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1
Quinlan, E. M., K. Gregory, and A. D. Murphy. "An identified glutamatergic interneuron patterns feeding motor activity via both excitation and inhibition." Journal of Neurophysiology 73, no. 3 (March 1, 1995): 945–56. http://dx.doi.org/10.1152/jn.1995.73.3.945.
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1. Previously we demonstrated that glutamate is an important neurotransmitter in the CNS of Helisoma. Exogenous glutamate applied to the buccal ganglia mimicked both the excitatory and inhibitory effects of subunit 2 (S2) of the tripartite central pattern generator (CPG) on S2 postsynaptic motor neurons. Here we identify buccal interneuron B2 as an S2 interneuron by utilizing a combination of electrophysiology, pharmacology, and intracellular staining. In addition, neurons that were electrophysiologically and morphologically characterized as neuron B2 demonstrated antiglutamate immunoreactivity, suggesting that neuron B2 is a source of endogenous glutamate in the buccal ganglia. 2. Depolarization of neuron B2 evoked excitatory postsynaptic potentials in motor neurons excited by S2. The excitatory effects of B2 depolarization and S2 activation were reversibly antagonized by the ionotropic glutamate receptor antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione, similar to the antagonism shown previously for application of exogenous glutamate. Depolarization of neuron B2 also evoked inhibitory postsynaptic potentials in motor neurons inhibited by S2. When such motor neurons were maintained in isolated cell culture, application of exogenous glutamate produced a direct hyperpolarization of the membrane potential. 3. The activity of neuron B2 is necessary for the production of the standard pattern of buccal motor neuron activity, which underlies functional feeding movements. The subunits of the tripartite buccal CPG must be active in the temporal sequence S1-S2-S3 to produce the standard feeding pattern. Rhythmic inhibition from neuron B2 terminated activity in S1 postsynaptic motor neurons and entrained the frequency of activity in S3 postsynaptic motor neurons. Hyperpolarization of neuron B2 disrupted the production of the standard motor pattern by eliminating S2 postsynaptic potentials in identified buccal motor neurons, thereby prolonging S1 activity and disrupting S3 bursting. 4. These data support the hypothesis that S2 neuron B2 is glutamatergic and demonstrate that glutamatergic transmission, and especially inhibition, is fundamental to the production of behaviorally critical motor neuron activity patterns in Helisoma.
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Segal, M. M. "Epileptiform activity in microcultures containing one excitatory hippocampal neuron." Journal of Neurophysiology 65, no. 4 (April 1, 1991): 761–70. http://dx.doi.org/10.1152/jn.1991.65.4.761.
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1. Paroxysmal depolarizing shifts (PDSs) occur during interictal epileptiform activity. Sustained depolarizations are characteristic of ictal activity, and events resembling PDSs also occur during the sustained depolarizations. To study these elements of epileptiform activity in a simpler context, I used the in vitro chronic-excitatory-block model of epilepsy of Furshpan and Potter and the microculture technique of Segal and Furshpan. 2. Intracellular recordings were made from 93 single-neuron microcultures. Forty of these solitary neurons were excitatory, their action potentials were replaced by PDS-like events or sustained depolarizations as kynurenate was removed from the perfusion solution. PDS-like events were similar to PDSs in intact cortex, mass cultures, and microcultures with more than one neuron. Small voltage fluctuations were also seen in solitary excitatory neurons in the absence of recorded action potentials. Sustained depolarizations developed in 5 of the 40 excitatory neurons. Forty-eight of the 93 solitary neurons were inhibitory, with bicuculline-sensitive hyperpolarizations after the action potential (ascribable to gamma-aminobutyric acid-A autapses). None of the solitary inhibitory neurons displayed sustained depolarizations. Five of the 93 neurons were insensitive to both kynurenate and bicuculline and were not placed in either the excitatory or the inhibitory category. 3. Both N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors contributed to the PDS-like events and sustained depolarizations. Only a non-NMDA glutamate receptor component was evident for the small voltage fluctuations. 4. Intracellular recordings were also made from two-neuron microcultures, each containing one excitatory neuron and one inhibitory neuron. Sustained depolarizations developed in five microcultures, in each case only in the excitatory neuron.
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Wang, Rubin, Ichiro Tsuda, and Zhikang Zhang. "A New Work Mechanism on Neuronal Activity." International Journal of Neural Systems 25, no. 03 (April 8, 2015): 1450037. http://dx.doi.org/10.1142/s0129065714500373.
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By re-examining the neuronal activity energy model, we show the inadequacies in the current understanding of the energy consumption associated with neuron activity. Specifically, we show computationally that a neuron first absorbs and then consumes energy during firing action potential, and this result cannot be produced from any current neuron models or biological neural networks. Based on this finding, we provide an explanation for the observation that when neurons are excited in the brain, blood flow increases significantly while the incremental oxygen consumption is very small. We can also explain why external stimulation and perception emergence are synchronized. We also show that negative energy presence in neurons at the sub-threshold state is an essential reason that leads to blood flow incremental response time in the brain rather than neural excitation to delay.
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Weaver, Adam L., and Scott L. Hooper. "Follower Neurons in Lobster (Panulirus interruptus) Pyloric Network Regulate Pacemaker Period in Complementary Ways." Journal of Neurophysiology 89, no. 3 (March 1, 2003): 1327–38. http://dx.doi.org/10.1152/jn.00704.2002.
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Distributed neural networks (ones characterized by high levels of interconnectivity among network neurons) are not well understood. Increased insight into these systems can be obtained by perturbing network activity so as to study the functions of specific neurons not only in the network's “baseline” activity but across a range of network activities. We applied this technique to study cycle period control in the rhythmic pyloric network of the lobster, Panulirus interruptus. Pyloric rhythmicity is driven by an endogenous oscillator, the Anterior Burster (AB) neuron. Two network neurons feed back onto the pacemaker, the Lateral Pyloric (LP) neuron by inhibition and the Ventricular Dilator (VD) neuron by electrical coupling. LP and VD neuron effects on pyloric cycle period can be studied across a range of periods by altering period by injecting current into the AB neuron and functionally removing (by hyperpolarization) the LP and VD neurons from the network at each period. Within a range of pacemaker periods, the LP and VD neurons regulate period in complementary ways. LP neuron removal speeds the network and VD neuron removal slows it. Outside this range, network activity is disrupted because the LP neuron cannot follow slow periods, and the VD neuron cannot follow fast periods. These neurons thus also limit, in complementary ways, normal pyloric activity to a certain period range. These data show that follower neurons in pacemaker networks can play central roles in controlling pacemaker period and suggest that in some cases specific functions can be assigned to individual network neurons.
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Spencer, Robert M., and Dawn M. Blitz. "Network feedback regulates motor output across a range of modulatory neuron activity." Journal of Neurophysiology 115, no. 6 (June 1, 2016): 3249–63. http://dx.doi.org/10.1152/jn.01112.2015.
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Modulatory projection neurons alter network neuron synaptic and intrinsic properties to elicit multiple different outputs. Sensory and other inputs elicit a range of modulatory neuron activity that is further shaped by network feedback, yet little is known regarding how the impact of network feedback on modulatory neurons regulates network output across a physiological range of modulatory neuron activity. Identified network neurons, a fully described connectome, and a well-characterized, identified modulatory projection neuron enabled us to address this issue in the crab ( Cancer borealis) stomatogastric nervous system. The modulatory neuron modulatory commissural neuron 1 (MCN1) activates and modulates two networks that generate rhythms via different cellular mechanisms and at distinct frequencies. MCN1 is activated at rates of 5–35 Hz in vivo and in vitro. Additionally, network feedback elicits MCN1 activity time-locked to motor activity. We asked how network activation, rhythm speed, and neuron activity levels are regulated by the presence or absence of network feedback across a physiological range of MCN1 activity rates. There were both similarities and differences in responses of the two networks to MCN1 activity. Many parameters in both networks were sensitive to network feedback effects on MCN1 activity. However, for most parameters, MCN1 activity rate did not determine the extent to which network output was altered by the addition of network feedback. These data demonstrate that the influence of network feedback on modulatory neuron activity is an important determinant of network output and feedback can be effective in shaping network output regardless of the extent of network modulation.
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Suri, Roland E., and Wolfram Schultz. "Temporal Difference Model Reproduces Anticipatory Neural Activity." Neural Computation 13, no. 4 (April 1, 2001): 841–62. http://dx.doi.org/10.1162/089976601300014376.
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Anticipatory neural activity preceding behaviorally important events has been reported in cortex, striatum, and midbrain dopamine neurons. Whereas dopamine neurons are phasically activated by reward-predictive stimuli, anticipatory activity of cortical and striatal neurons is increased during delay periods before important events. Characteristics of dopa-mine neuron activity resemble those of the prediction error signal of the temporal difference (TD) model of Pavlovian learning (Sutton & Barto, 1990). This study demonstrates that the prediction signal of the TD model reproduces characteristics of cortical and striatal anticipatory neural activity. This finding suggests that tonic anticipatory activities may reflect prediction signals that are involved in the processing of dopamine neuron activity.
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Park, Jihoon, Koki Ichinose, Yuji Kawai, Junichi Suzuki, Minoru Asada, and Hiroki Mori. "Macroscopic Cluster Organizations Change the Complexity of Neural Activity." Entropy 21, no. 2 (February 23, 2019): 214. http://dx.doi.org/10.3390/e21020214.
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In this study, simulations are conducted using a network model to examine how the macroscopic network in the brain is related to the complexity of activity for each region. The network model is composed of multiple neuron groups, each of which consists of spiking neurons with different topological properties of a macroscopic network based on the Watts and Strogatz model. The complexity of spontaneous activity is analyzed using multiscale entropy, and the structural properties of the network are analyzed using complex network theory. Experimental results show that a macroscopic structure with high clustering and high degree centrality increases the firing rates of neurons in a neuron group and enhances intraconnections from the excitatory neurons to inhibitory neurons in a neuron group. As a result, the intensity of the specific frequency components of neural activity increases. This decreases the complexity of neural activity. Finally, we discuss the research relevance of the complexity of the brain activity.
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Hu, Xiaoyu, and Chongxin Liu. "Bursting and Synchronization of Coupled Neurons under Electromagnetic Radiation." Complexity 2019 (December 4, 2019): 1–10. http://dx.doi.org/10.1155/2019/4835379.
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Bursting is an important firing activity of neurons, which is caused by a slow process that modulates fast spiking activity. Based on the original second-order Morris-Lecar neuron model, an improved third-order Morris-Lecar neuron model can produce bursting activity is proposed, in which the effect of electromagnetic radiation is considered as a slow process and the original equation of Morris-Lecar neuron model as a fast process. Extensive numerical simulation results show that the improved neuron model can produce different types of bursting, and bursting activity shows a deep dependence on system parameters and electromagnetic radiation parameters. In addition, synchronization transitions of identical as well as no-identical coupled third-order Morris-Lecar neurons are studied, the results show that identical coupled neurons experience a complex synchronization process and reach complete synchronization finally with the increase of coupling intensity. For no-identical coupled neurons, only anti-phase synchronization and in-phase synchronization can be reached. The studies of bursting activity of single neuron and synchronization transition of coupled neurons have important guiding significance for further understanding the information processing of neurons and collective behaviors in neuronal network under electromagnetic radiation environment.
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Hooper, S. L., and M. Moulins. "Cellular and synaptic mechanisms responsible for a long-lasting restructuring of the lobster pyloric network." Journal of Neurophysiology 64, no. 5 (November 1, 1990): 1574–89. http://dx.doi.org/10.1152/jn.1990.64.5.1574.
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1. In the lobster Palinurus vulgaris a sensory input in the lateral posterolateral nerve (lpln) of the stomatogastric nervous system (STS) is able to turn on the cardiac sac (CS) network and to induce dramatic long-lasting alterations in the output of the pyloric network. This long-lasting alteration of pyloric network output consists primarily of changes in the activity of the two neurons that innervate the muscles of the cardiopyloric valve of the stomach, with the dilator neuron (the ventricular dilator, VD) transferring from the pyloric network to the CS network and the constrictor neuron (the inferior cardiac, IC) shifting to fire earlier in the pyloric pattern. 2. The inferior ventricular (IV) neurons of the CS network make complex multiaction synaptic connections onto several pyloric neurons in a related species, Panulirus interruptus. We show that many of the short-term alterations in pyloric activity observed during CS network bursts in Palinurus are due to similar IV neuron synaptic connections. However, the long-lasting effects of lpln stimulation on pyloric output are not due to this synaptic input, because 1) direct activation of the IV neurons does not induce long-lasting changes in pyloric activity and 2) pharmacologic disconnection of this synaptic input does not abolish lpln stimulation's long-lasting effects. Lpln stimulation therefore activates two different neuronal inputs to the pyloric network. 3. The transfer of the VD neuron from the pyloric to the CS network is the result of the concerted actions of these two inputs. Lpln stimulation turns on the CS network, and the IV neurons of the CS network excite the VD neuron and ensure it fires with the CS network. The second neuronal input (that not involving known CS network neurons) abolishes in a long-lasting fashion the VD neuron regenerative (plateau) properties, and thus suppresses the ability of the VD neuron to participate in the pyloric rhythmic pattern between CS network bursts. 4. Experimental manipulation of VD neuron activity can both mimic and reverse the effects of lpln stimulation on the IC neuron. The changes in IC neuron activity are therefore not due to direct lpln-activated synaptic input onto the IC neuron, but instead are indirect "network" effects arising from the changes in VD neuron activity.
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Weaver, Adam L., and Scott L. Hooper. "Relating Network Synaptic Connectivity and Network Activity in the Lobster (Panulirus interruptus) Pyloric Network." Journal of Neurophysiology 90, no. 4 (October 2003): 2378–86. http://dx.doi.org/10.1152/jn.00705.2002.
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The lobster pyloric network has a densely interconnected synaptic connectivity pattern, and the role individual synapses play in generating network activity is consequently difficult to discern. We examined this issue by quantifying the effect on pyloric network phasing and spiking activity of removing the Lateral Pyloric (LP) and Ventricular Dilator (VD) neurons, which synapse onto almost all pyloric neurons. A confounding factor in this work is that LP and VD neuron removal alters pyloric cycle period. To determine the effects of LP and VD neuron removal on pyloric activity independent of these period alterations, we altered network period by current injection into a pyloric pacemaker neuron, hyperpolarized the LP or VD neuron to functionally remove each from the network, and plotted various measures of pyloric neuron activity against period with and without the LP or VD neuron. In normal physiological saline, in many (or most) cases removing either neuron had surprisingly little effect on the activity of its postsynaptic partners, which suggests that under these conditions these neurons play a relatively small role in determining pyloric activity. In the cases in which removal did alter postsynaptic activity, the effects were inconsistent across preparations, which suggests that either despite producing very similar neural outputs, pyloric networks from different animals have different cellular and synaptic properties, or some synapses contribute to network activity only under certain modulatory conditions, and the “baseline” level of modulatory influence the network receives from higher centers varies from animal to animal.
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Burdakov, Denis, and Mahesh Karnani. "Orexin neuron activity in mating mice - a pilot study." Neuroanatomy and Behaviour 3 (June 2, 2021): e17. http://dx.doi.org/10.35430/nab.2021.e17.
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Mating behaviours affect hypothalamic orexin/hypocretin neurons and vice versa. However, activity of orexin neurons has not been recorded during mating before. We report an anecdotal dataset of freely-moving miniature microscope recordings of orexin neuron activity during mating behaviours, as well as an oral sexual encounter previously undocumented in mice. Across the orexin neuron population in the male, firing rates were maximally diverse during ejaculation, similarly diverse though weaker during intromission, and inverse to this during anterior thrusting. In the female mouse, orexin neurons tended to decrease firing during intromission after a transient increase. We provide this brief dataset for re-use, to enable further studies of these rare behaviours with challenging surgical preparations.
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Azhar, Feraz, and William S. Anderson. "Predicting Single-Neuron Activity in Locally Connected Networks." Neural Computation 24, no. 10 (October 2012): 2655–77. http://dx.doi.org/10.1162/neco_a_00343.
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The characterization of coordinated activity in neuronal populations has received renewed interest in the light of advancing experimental techniques that allow recordings from multiple units simultaneously. Across both in vitro and in vivo preparations, nearby neurons show coordinated responses when spontaneously active and when subject to external stimuli. Recent work (Truccolo, Hochberg, & Donoghue, 2010 ) has connected these coordinated responses to behavior, showing that small ensembles of neurons in arm-related areas of sensorimotor cortex can reliably predict single-neuron spikes in behaving monkeys and humans. We investigate this phenomenon using an analogous point process model, showing that in the case of a computational model of cortex responding to random background inputs, one is similarly able to predict the future state of a single neuron by considering its own spiking history, together with the spiking histories of randomly sampled ensembles of nearby neurons. This model exhibits realistic cortical architecture and displays bursting episodes in the two distinct connectivity schemes studied. We conjecture that the baseline predictability we find in these instances is characteristic of locally connected networks more broadly considered.
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Schieber, Marc H., and Gil Rivlis. "Partial Reconstruction of Muscle Activity From a Pruned Network of Diverse Motor Cortex Neurons." Journal of Neurophysiology 97, no. 1 (January 2007): 70–82. http://dx.doi.org/10.1152/jn.00544.2006.
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Primary motor cortex (M1) neurons traditionally have been viewed as “upper motor neurons” that directly drive spinal motoneuron pools, particularly during finger movements. We used spike-triggered averages (SpikeTAs) of electromyographic (EMG) activity to select M1 neurons whose spikes signaled the arrival of input in motoneuron pools, and examined the degree of similarity between the activity patterns of these M1 neurons and their target muscles during 12 individuated finger and wrist movements. Neuron–EMG similarity generally was low. Similarity was unrelated to the strength of the SpikeTA effect, to whether the effect was pure versus synchrony, or to the number of muscles influenced by the neuron. Nevertheless, the sum of M1 neuron activity patterns, each weighted by the sign and strength of its SpikeTA effect, could be more similar to the EMG than the average similarity of individual neurons. Significant correlations between the weighted sum of M1 neuron activity patterns and EMG were obtained in six of 17 muscles, but showed R2 values ranging from only 0.26 to 0.42. These observations suggest that additional factors—including inputs from sources other than M1 and nonlinear summation of inputs to motoneuron pools—also contributed substantially to EMG activity patterns. Furthermore, although each of these M1 neurons produced SpikeTA effects with a significant peak or trough 6–16 ms after the triggering spike, shifting the weighted sum of neuron activity to lead the EMG by 40–60 ms increased their similarity, suggesting that the influence of M1 neurons that produce SpikeTA effects includes substantial synaptic integration that in part may reach the motoneuron pools over less-direct pathways.
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Mazurek, Kevin A., and Marc H. Schieber. "Mirror neurons precede non-mirror neurons during action execution." Journal of Neurophysiology 122, no. 6 (December 1, 2019): 2630–35. http://dx.doi.org/10.1152/jn.00653.2019.
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Mirror neurons are thought to represent an individual’s ability to understand the actions of others by discharging as one individual performs or observes another individual performing an action. Studies typically have focused on mirror neuron activity during action observation, examining activity during action execution primarily to validate mirror neuron involvement in the motor act. As a result, little is known about the precise role of mirror neurons during action execution. In this study, during execution of reach-grasp-manipulate movements, we found activity of mirror neurons generally preceded that of non-mirror neurons. Not only did the onset of task-related modulation occur earlier in mirror neurons, but state transitions detected by hidden Markov models also occurred earlier in mirror neuron populations. Our findings suggest that mirror neurons may be at the forefront of action execution. NEW & NOTEWORTHY Mirror neurons commonly are thought to provide a neural substrate for understanding the actions of others, but mirror neurons also are active during action execution, when additional, non-mirror neurons are active as well. Examining the timing of activity during execution of a naturalistic reach-grasp-manipulate task, we found that mirror neuron activity precedes that of non-mirror neurons at both the unit and the population level. Thus mirror neurons may be at the leading edge of action execution.
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Thuma, Jeff B., and Scott L. Hooper. "Quantification of Cardiac Sac Network Effects on a Movement-Related Parameter of Pyloric Network Output in the Lobster." Journal of Neurophysiology 89, no. 2 (February 1, 2003): 745–53. http://dx.doi.org/10.1152/jn.00631.2002.
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Cardiac sac network activity (cycle period tens of seconds to minutes) has long been known to alter pyloric network activity (cycle period approximately 1 s), but these effects have not been quantified. Some pyloric muscles extract cardiac sac timed variations in pyloric motor neuron firing, and consequently produce cardiac sac timed movements even though no cardiac sac neurons innervate them. Determining pyloric behavior therefore requires detailed description of cardiac sac effects on pyloric neural output. Pyloric muscle activity correlates well with motor neuron overall spike frequency (OSF, number of spikes per burst divided by cycle period). We therefore quantified the effects of cardiac sac activity on the OSF of all pyloric neurons in the lobster, Panulirus interruptus. The ventricular dilator (VD) neuron had a biphasic response, with its OSF first increasing and then decreasing during cardiac sac bursts. Lateral pyloric (LP) neuron OSF decreased during cardiac sac activity. The pyloric (PY) neurons had two responses, with OSF either decreasing or increasing just after the beginning of cardiac sac activity. The pyloric dilator (PD) neurons had a triphasic response, with OSF increasing slightly at the beginning of cardiac sac activity, decreasing during the cardiac sac burst, and strongly increasing after cardiac sac activity ended. The inferior cardiac (IC) neuron had a biphasic response, with OSF decreasing at the beginning of cardiac sac activity and strongly increasing when cardiac sac activity ceased. These data provide the quantitative description of cardiac sac effects on pyloric activity necessary to predict pyloric movement from pyloric neural output.
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Zhang, Mengliang, and Kevin D. Alloway. "Stimulus-Induced Intercolumnar Synchronization of Neuronal Activity in Rat Barrel Cortex: A Laminar Analysis." Journal of Neurophysiology 92, no. 3 (September 2004): 1464–78. http://dx.doi.org/10.1152/jn.01272.2003.
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We used cross-correlation analysis to characterize the coordination of stimulus-induced neuronal activity in the primary somatosensory barrel cortex of isoflurane-anesthetized rats. On each trial, multiple whiskers were simultaneously deflected at frequencies that corresponded to 2, 5, 8, or 11 Hz. Among 476 neuron pairs that we examined, 342 (71.8%) displayed significant peaks of synchronized activity that exceeded the 99.9% confidence limits. The incidence and strength of these functional associations varied across different cortical layers. Only 52.9% of neuron pairs in layer IV displayed synchronized responses, whereas 84.1% of the infragranular neuron pairs were synchronized during whisker stimulation. Neuronal synchronization was strongest in the infragranular layers, weakest in layer IV, and varied according to the columnar configuration of the neuron pairs. Thus correlation coefficients were largest for neuron pairs in the same whisker barrel row but were smallest for neurons in different rows and arcs. Spontaneous activity in the infragranular layers was also synchronized to a greater degree than in the other layers. Although infragranular neuron pairs displayed similar amounts of synchronization in response to each stimulus frequency, granular and supragranular neurons were synchronized mainly during stimulation at 2 or 5 Hz. These results are consistent with previous studies indicating that infragranular neurons have intrinsic properties that facilitate synchronized activity, and they suggest that neuronal synchronization plays an important role in transmitting sensory information to other cortical or subcortical brain regions.
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Awal, Mehraj R., Doug Austin, Jeremy Florman, Mark Alkema, Christopher V. Gabel, and Christopher W. Connor. "Breakdown of Neural Function under Isoflurane Anesthesia." Anesthesiology 129, no. 4 (October 1, 2018): 733–43. http://dx.doi.org/10.1097/aln.0000000000002342.
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Abstract Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Previous work on the action of volatile anesthetics has focused at either the molecular level or bulk neuronal measurement such as electroencephalography or functional magnetic resonance imaging. There is a distinct gulf in resolution at the level of cellular signaling within neuronal systems. The authors hypothesize that anesthesia is caused by induced dyssynchrony in cellular signaling rather than suppression of individual neuron activity. Methods Employing confocal microscopy and Caenorhabditis elegans expressing the calcium-sensitive fluorophore GCaMP6s in specific command neurons, the authors measure neuronal activity noninvasively and in parallel within the behavioral circuit controlling forward and reverse crawling. The authors compare neuronal dynamics and coordination in a total of 31 animals under atmospheres of 0, 4, and 8% isoflurane. Results When not anesthetized, the interneurons controlling forward or reverse crawling occupy two possible states, with the activity of the “reversal” neurons AVA, AVD, AVE, and RIM strongly intercorrelated, and the “forward” neuron AVB anticorrelated. With exposure to 4% isoflurane and onset of physical quiescence, neuron activity wanders rapidly and erratically through indeterminate states. Neuron dynamics shift toward higher frequencies, and neuron pair correlations within the system are reduced. At 8% isoflurane, physical quiescence continues as neuronal signals show diminished amplitude with little correlation between neurons. Neuronal activity was further studied using statistical tools from information theory to quantify the type of disruption caused by isoflurane. Neuronal signals become noisier and more disordered, as measured by an increase in the randomness of their activity (Shannon entropy). The coordination of the system, measured by whether information exhibited in one neuron is also exhibited in other neurons (multiinformation), decreases significantly at 4% isoflurane (P = 0.00015) and 8% isoflurane (P = 0.0028). Conclusions The onset of anesthesia corresponds with high-frequency randomization of individual neuron activity coupled with induced dyssynchrony and loss of coordination between neurons that disrupts functional signaling.
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Adams, E. M., A. D. Horres, and R. Frayser. "Inspiratory neuron activity in the ventrolateral medulla of the dog." Journal of Applied Physiology 62, no. 1 (January 1, 1987): 335–43. http://dx.doi.org/10.1152/jappl.1987.62.1.335.
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The purpose of this study was to describe the distribution and activity pattern of respiratory neurons located in the ventrolateral medulla (VLM) of the dog. Spike activity of 129 respiratory neurons was recorded in 23 ketamine-anesthetized spontaneously breathing dogs. Pontamine blue dye was used to mark the location of each neuron. Most VLM neurons displaying respiratory related spike patterns were located in a column related closely to ambigual and retroambigual nuclei. Both inspiratory and expiratory neurons were present with inspiratory units being grouped more rostrally. The predominant inspiratory neuron firing pattern was “late” inspiratory, although eight “early” types were located. All expiratory firing patterns were the late expiratory variety. Each neuron burst pattern was characterized by determining burst duration (BD), spikes per burst (S/B), peak frequency (PF), time to peak frequency (TPF), rate of rise to peak frequency (PF/TPF), and mean frequency. CO2-induced minute ventilation increases were associated with decreases in BD and TPF and increases in PF, S/B, and PF/TPF. In 11 experiments the relative influences of vagotomy and tracheal occlusion on late inspiratory units were compared. Tracheal occlusion increased late inspiratory BD and S/B but did not alter PF/TPF. Vagotomy increased BD and S/B beyond those obtained by tracheal occlusion and, in some neurons, decreased the PF/TPF. We conclude that the location of respiratory units in the VLM of the dog is similar to that in other species, the discharge pattern of VLM respiratory units is similar to those in cat VLM, and vagotomy and tracheal occlusion affect discharge patterns differently.
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YAMAZAKI, TADASHI, and SHIGERU TANAKA. "A NEURAL NETWORK MODEL FOR TRACE CONDITIONING." International Journal of Neural Systems 15, no. 01n02 (February 2005): 23–30. http://dx.doi.org/10.1142/s0129065705000037.
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We studied the dynamics of a neural network that has both recurrent excitatory and random inhibitory connections. Neurons started to become active when a relatively weak transient excitatory signal was presented and the activity was sustained due to the recurrent excitatory connections. The sustained activity stopped when a strong transient signal was presented or when neurons were disinhibited. The random inhibitory connections modulated the activity patterns of neurons so that the patterns evolved without recurrence with time. Hence, a time passage between the onsets of the two transient signals was represented by the sequence of activity patterns. We then applied this model to represent the trace eyeblink conditioning, which is mediated by the hippocampus. We assumed this model as CA3 of the hippocampus and considered an output neuron corresponding to a neuron in CA1. The activity pattern of the output neuron was similar to that of CA1 neurons during trace eyeblink conditioning, which was experimentally observed.
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Church, P. J., and P. E. Lloyd. "Activity of multiple identified motor neurons recorded intracellularly during evoked feedinglike motor programs in Aplysia." Journal of Neurophysiology 72, no. 4 (October 1, 1994): 1794–809. http://dx.doi.org/10.1152/jn.1994.72.4.1794.
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1. The firing patterns of 22 motor neurons were determined by simultaneously recording intracellularly from up to 7 neurons during evoked feedinglike buccal motor programs (BMPs). Intracellular stimulation of cerebral-buccal interneuron 2 (CBI-2) or tactile stimulation of the odontophore were used to elicit BMPs in a reduced preparation. 2. Evoked BMPs were identified as either ingestive-like (iBMP) or egestive-like (eBMP) on the basis of their similarity to those previously recorded in select neurons in freely behaving animals. Neurons were divided into the p-group, r-group, or c-group, on the basis of the phase relationships of rhythmic membrane depolarizations and hyperpolarizations during evoked BMPs. Depolarization of the p-, r-, and c-group neurons was associated with radular protraction, retraction, and closure, respectively. With one exception, the motor neurons segregated into the same groups during iBMPs and eBMPs. The exception, B7, was categorized as a c-group neuron during iBMPs, but as an r-group neuron during eBMPs. 3. Every motor neuron exhibited cyclic membrane depolarizations and hyperpolarizations, and over one-half of the neurons fired bursts of action potentials, during both iBMPs and eBMPs. The neurons fired in patterns that would be likely to release both their conventional and peptide transmitters. 4. A marked hyperpolarizing step in the p-group neurons coincident with a depolarization in the r-group neurons was observed during both iBMPs and eBMPs, suggesting a degree of shared premotor circuitry for the two BMPs. 5. A shift in the timing of activity in c-group neurons relative to that in p- and r-group neurons during iBMPs and eBMPs was observed and correlates well with the shift in phase of radular closure relative to protraction and retraction, which is useful in distinguishing ingestion from egestion in the behaving animal. 6. The firing patterns recorded in neurons that innervate overlapping populations of muscle fibers suggested that there would be complex interactions of multiple transmitters. This is particularly intriguing in the case of I3a muscle fibers, which are innervated by two excitatory and one inhibitory neuron. The firing patterns recorded in these neurons suggest that the inhibitory motor neuron may serve to not only block inappropriate contractions, but also to specifically shape evoked contractions during feeding.
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Chen, Li, and Daniel J. Lodge. "The lateral mesopontine tegmentum regulates both tonic and phasic activity of VTA dopamine neurons." Journal of Neurophysiology 110, no. 10 (November 15, 2013): 2287–94. http://dx.doi.org/10.1152/jn.00307.2013.
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Anatomic studies have demonstrated that the mesolimbic dopamine system receives a substantial afferent input from a variety of regions ranging from the prefrontal cortex through to the brain stem. However, how these afferents regulate dopamine neuron activity is still largely unknown. The mesopontine tegmentum provides a significant input to ventral tegmental area (VTA) dopamine neurons, and it has been demonstrated that discrete subdivisions within this region differentially alter dopamine neuron activity. Thus the laterodorsal tegmental nucleus provides a tonic input essential for maintaining burst firing of dopamine neurons, whereas the pedunculopontine tegmental (PPTg) nucleus regulates a transition from single-spike firing to burst firing. In contrast, the recently identified rostromedial tegmental nucleus provides an inhibitory input to the VTA and decreases spontaneous dopamine neuron activity. Here, we demonstrate that an area adjacent to the PPTg regulates both population activity as well as burst firing of VTA dopamine neurons. Specifically, N-methyl-d-aspartic acid (NMDA) activation of the lateral mesopontine tegmentum produces an increase in the number of spontaneously active dopamine neurons and an increase in the average percentage of burst firing of dopamine neurons. This increase in neuronal activity was correlated with extracellular dopamine efflux in the nucleus accumbens, as measured by in vivo microdialysis. Taken together, we provide further evidence that the mesopontine tegmentum regulates discrete dopamine neuron activity states that are relevant for the understanding of dopamine system function in both normal and disease states.
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Yu, Ruichi, Jui-Hsin (Larry) Lai, Shun-Xuan Wang, and Ching-Yung Lin. "Brain Neuron Network Extraction and Analysis of Live Mice from Imaging Videos." International Journal of Multimedia Data Engineering and Management 8, no. 3 (July 2017): 1–20. http://dx.doi.org/10.4018/ijmdem.2017070101.
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Modern brain mapping techniques are producing increasingly large datasets of anatomical or functional connection patterns. Recently, it became possible to record detailed live imaging videos of mammal brain while the subject is engaging routine activity. We analyze videos recorded from ten mice to describe how to detect neurons, extract neuron signals, map correlation of neuron signals to mice activity, detect the network topology of active neurons, and analyze network topology characteristics. We propose a neuron position alignment method to compensate the distortion and movement of cerebral cortex in live mouse brain and the background luminance compensation to extract and model neuron activity. To find out the network topology, a cross-correlation based method and a causal Bayesian network method are proposed and used for analysis. Afterwards, we did preliminary analysis on network topologies. The significance of this paper is on how to extract neuron activities from live mouse brain imaging videos and a network analysis method to analyze its topology.
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Quinlan, E. M., and A. D. Murphy. "Plasticity in the multifunctional buccal central pattern generator of Helisoma illuminated by the identification of phase 3 interneurons." Journal of Neurophysiology 75, no. 2 (February 1, 1996): 561–74. http://dx.doi.org/10.1152/jn.1996.75.2.561.
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1. The mechanism for generating diverse patterns of buccal motor neuron activity was explored in the multifunctional central pattern generator (CPG) of Helisoma. The standard pattern of motor neuron activity, which results in typical feeding behavior, consists of three distinct phases of buccal motor neuron activity. We have previously identified CPG interneurons that control the motor neuron activity during phases 1 and 2 of the standard pattern. Here we identify a pair of interneurons responsible for buccal motor neuron activity during phase 3, and examine the variability in the interactions between this third subunit and other subunits of the CPG. 2. During the production of the standard pattern, phase 3 excitation in many buccal motor neurons follows a prominent phase 2 inhibitory postsynaptic potential. Therefore phase 3 excitation was previously attributed to postinhibitory rebound (PIR) in these motor neurons. Two classes of observations indicated that PIR was insufficient to account for phase 3 activity, necessitating phase 3 interneurons. 1) A subset of identified buccal neurons is inhibited during phase 3 by discrete synaptic input. 2) Other identified buccal neurons display discrete excitation during both phases 2 and 3. 3. A bilaterally symmetrical pair of CPG interneurons, named N3a, was identified and characterized as the source of phase 3 postsynaptic potentials in motor neurons. During phase 3 of the standard motor pattern, interneuron N3a generated bursts of action potentials. Stimulation of N3a, in quiescent preparations, evoked a depolarization in motor neurons that are excited during phase 3 and a hyperpolarization in motor neurons that are inhibited during phase 3. Hyperpolarization of N3a during patterned motor activity eliminated both phase 3 excitation and inhibition. Physiological and morphological characterization of interneuron N3a is provided to invite comparisons with possible homologues in other gastropod feeding CPGs. 4. These data support a model proposed for the organization of the tripartite buccal CPG. According to the model, each of the three phases of buccal motor neuron activity is controlled by discrete subsets of pattern-generating interneurons called subunit 1 (S1), subunit 2 (S2), and subunit 3 (S3). The standard pattern of buccal motor neuron activity underlying feeding is mediated by an S1-S2-S3 sequence of CPG subunit activity. However, a number of "nonstandard" patterns of buccal motor activity were observed. In particular, S2 and S3 activity can occur independently or be linked sequentially in rhythmic patterns other than the standard feeding pattern. Simultaneous recordings of S3 interneuron N3a with effector neurons indicated that N3a can account for phase-3-like postsynaptic potentials (PSPs) in nonstandard patterns. The variety of patterns of buccal motor neuron activity indicates that each CPG subunit can be active in the absence of, or in concert with, activity in any other subunit. 5. To explore how CPG activity may be regulated to generate a particular motor pattern from the CPG's full repertoire, we applied the neuromodulator serotonin. Serotonin initiated and sustained the production of an S2-S3 pattern of activity, in part by enhancing PIR in S3 interneuron N3a after the termination of phase 2 inhibition.
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Dilsiz, Pelin, Iltan Aklan, Nilufer Sayar Atasoy, Yavuz Yavuz, Gizem Filiz, Fulya Koksalar, Tayfun Ates, et al. "MCH Neuron Activity Is Sufficient for Reward and Reinforces Feeding." Neuroendocrinology 110, no. 3-4 (June 3, 2019): 258–70. http://dx.doi.org/10.1159/000501234.
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Background: Melanin-concentrating hormone (MCH)-expressing neurons have been implicated in regulation of energy homeostasis and reward, yet the role of their electrical activity in short-term appetite and reward modulation has not been fully understood. Objectives: We investigated short-term behavioral and physiological effects of MCH neuron activity manipulations. Methods: We used optogenetic and chemogenetic approaches in Pmch-cre transgenic mice to acutely stimulate/inhibit MCH neuronal activity while probing feeding, locomotor activity, anxiety-like behaviors, glucose homeostasis, and reward. Results: MCH neuron activity is neither required nor sufficient for short-term appetite unless stimulation is temporally paired with consumption. MCH neuronal activation does not affect short-term locomotor activity, but inhibition improves glucose tolerance and is mildly anxiolytic. Finally, using two different operant tasks, we showed that activation of MCH neurons alone is sufficient to induce reward. Conclusions: Our results confirm diverse behavioral/physiological functions of MCH neurons and suggest a direct role in reward function.
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Mlinar, Boris, Alberto Montalbano, Gilda Baccini, Francesca Tatini, Rolando Berlinguer Palmini, and Renato Corradetti. "Nonexocytotic serotonin release tonically suppresses serotonergic neuron activity." Journal of General Physiology 145, no. 3 (February 23, 2015): 225–51. http://dx.doi.org/10.1085/jgp.201411330.
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The firing activity of serotonergic neurons in raphe nuclei is regulated by negative feedback exerted by extracellular serotonin (5-HT)o acting through somatodendritic 5-HT1A autoreceptors. The steady-state [5-HT]o, sensed by 5-HT1A autoreceptors, is determined by the balance between the rates of 5-HT release and reuptake. Although it is well established that reuptake of 5-HTo is mediated by 5-HT transporters (SERT), the release mechanism has remained unclear. It is also unclear how selective 5-HT reuptake inhibitor (SSRI) antidepressants increase the [5-HT]o in raphe nuclei and suppress serotonergic neuron activity, thereby potentially diminishing their own therapeutic effect. Using an electrophysiological approach in a slice preparation, we show that, in the dorsal raphe nucleus (DRN), continuous nonexocytotic 5-HT release is responsible for suppression of phenylephrine-facilitated serotonergic neuron firing under basal conditions as well as for autoinhibition induced by SSRI application. By using 5-HT1A autoreceptor-activated G protein–gated inwardly rectifying potassium channels of patched serotonergic neurons as 5-HTo sensors, we show substantial nonexocytotic 5-HT release under conditions of abolished firing activity, Ca2+ influx, vesicular monoamine transporter 2–mediated vesicular accumulation of 5-HT, and SERT-mediated 5-HT transport. Our results reveal a cytosolic origin of 5-HTo in the DRN and suggest that 5-HTo may be supplied by simple diffusion across the plasma membrane, primarily from the dense network of neurites of serotonergic neurons surrounding the cell bodies. These findings indicate that the serotonergic system does not function as a sum of independently acting neurons but as a highly interdependent neuronal network, characterized by a shared neurotransmitter pool and the regulation of firing activity by an interneuronal, yet activity-independent, nonexocytotic mechanism.
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West, Katherine Stuhrman, and Aaron G. Roseberry. "Neuropeptide-Y alters VTA dopamine neuron activity through both pre- and postsynaptic mechanisms." Journal of Neurophysiology 118, no. 1 (July 1, 2017): 625–33. http://dx.doi.org/10.1152/jn.00879.2016.
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The mesocorticolimbic dopamine system, the brain’s reward system, regulates many different behaviors including food intake, food reward, and feeding-related behaviors, and there is increasing evidence that hypothalamic feeding-related neuropeptides alter dopamine neuron activity to affect feeding. For example, neuropeptide-Y (NPY), a strong orexigenic hypothalamic neuropeptide, increases motivation for food when injected into the ventral tegmental area (VTA). How NPY affects the activity of VTA dopamine neurons to regulate feeding behavior is unknown, however. In these studies we have used whole cell patch-clamp electrophysiology in acute brain slices from mice to examine how NPY affects VTA dopamine neuron activity. NPY activated an outward current that exhibited characteristics of a G protein-coupled inwardly rectifying potassium channel current in ~60% of dopamine neurons tested. In addition to its direct effects on VTA dopamine neurons, NPY also decreased the amplitude and increased paired-pulse ratios of evoked excitatory postsynaptic currents in a subset of dopamine neurons, suggesting that NPY decreases glutamatergic transmission through a presynaptic mechanism. Interestingly, NPY also strongly inhibited evoked inhibitory postsynaptic currents onto dopamine neurons by a presynaptic mechanism. Overall these studies demonstrate that NPY utilizes multiple mechanisms to affect VTA dopamine neuron activity, and they provide an important advancement in our understanding of how NPY acts in the VTA to control feeding behavior. NEW & NOTEWORTHY Neuropeptide-Y (NPY) has been shown to act on mesolimbic dopamine circuits to increase motivated behaviors toward food, but it is unclear exactly how NPY causes these responses. Here, we demonstrate that NPY directly inhibited a subset of ventral tegmental area (VTA) dopamine neurons through the activation of G protein-coupled inwardly rectifying potassium currents, and it inhibited both excitatory postsynaptic currents and inhibitory postsynaptic currents onto subsets of dopamine neurons through a presynaptic mechanism. Thus NPY uses multiple mechanisms to dynamically control VTA dopamine neuron activity.
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Onimaru, Hiroshi, Yuko Kumagawa, and Ikuo Homma. "Respiration-Related Rhythmic Activity in the Rostral Medulla of Newborn Rats." Journal of Neurophysiology 96, no. 1 (July 2006): 55–61. http://dx.doi.org/10.1152/jn.01175.2005.
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There are at least two respiration-related rhythm generators in the medulla: the pre-Bötzinger complex, which produces inspiratory (Insp) neuron bursts, and the parafacial respiratory group (pFRG), which produces predominantly preinspiratory (Pre-I) neuron bursts. The pFRG Pre-I neuron activity has not been correlated with motor neuron activity in slice or block preparations of rostral medulla. In this study, we attempted to detect pFRG Pre-I activity as motor output in the rostral medulla. We recorded respiratory activity of the facial nerve in the brain stem–spinal cord preparation of 0- to 2-day-old rats. Facial nerve activity consisted of preinspiratory, Insp, and postinspiratory activity. Pre- and postinspiratory activity corresponded well with membrane potential trajectories of Pre-I neurons in the rostral ventrolateral medulla. In response to perfusion of 1 μM DAMGO (a μ-opiate agonist), fourth cervical ventral root (C4) Insp activity was depressed and facial nerve activity continued to synchronize with Pre-I neuron bursts. After transverse sectioning between the levels of the pre-Bötzinger complex and the pFRG, C4 Insp activity recovered within 15 min, but facial nerve activity was inhibited. When DAMGO was applied, C4 Insp activity was inhibited, and rhythmic facial nerve activity recovered. Subsequent elevation of K+ concentration reinduced C4 activity, but facial nerve activity was inhibited. Whole cell recordings in the rostral block revealed the presence of putative Pre-I neurons, the activity of which was synchronized with facial nerve activity. These results show that the rostral medulla, not including the pre-Bötzinger complex, produces Pre-I–like rhythmic activity that can be monitored as facial nerve motor output in newborn rat in vitro preparations.
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Morozova, Ekaterina O., Maxym Myroshnychenko, Denis Zakharov, Matteo di Volo, Boris Gutkin, Christopher C. Lapish, and Alexey Kuznetsov. "Contribution of synchronized GABAergic neurons to dopaminergic neuron firing and bursting." Journal of Neurophysiology 116, no. 4 (October 1, 2016): 1900–1923. http://dx.doi.org/10.1152/jn.00232.2016.
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In the ventral tegmental area (VTA), interactions between dopamine (DA) and γ-aminobutyric acid (GABA) neurons are critical for regulating DA neuron activity and thus DA efflux. To provide a mechanistic explanation of how GABA neurons influence DA neuron firing, we developed a circuit model of the VTA. The model is based on feed-forward inhibition and recreates canonical features of the VTA neurons. Simulations revealed that γ-aminobutyric acid (GABA) receptor (GABAR) stimulation can differentially influence the firing pattern of the DA neuron, depending on the level of synchronization among GABA neurons. Asynchronous activity of GABA neurons provides a constant level of inhibition to the DA neuron and, when removed, produces a classical disinhibition burst. In contrast, when GABA neurons are synchronized by common synaptic input, their influence evokes additional spikes in the DA neuron, resulting in increased measures of firing and bursting. Distinct from previous mechanisms, the increases were not based on lowered firing rate of the GABA neurons or weaker hyperpolarization by the GABAR synaptic current. This phenomenon was induced by GABA-mediated hyperpolarization of the DA neuron that leads to decreases in intracellular calcium (Ca2+) concentration, thus reducing the Ca2+-dependent potassium (K+) current. In this way, the GABA-mediated hyperpolarization replaces Ca2+-dependent K+ current; however, this inhibition is pulsatile, which allows the DA neuron to fire during the rhythmic pauses in inhibition. Our results emphasize the importance of inhibition in the VTA, which has been discussed in many studies, and suggest a novel mechanism whereby computations can occur locally.
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Amari, Shun-ichi, Hiroyuki Nakahara, Si Wu, and Yutaka Sakai. "Synchronous Firing and Higher-Order Interactions in Neuron Pool." Neural Computation 15, no. 1 (January 1, 2003): 127–42. http://dx.doi.org/10.1162/089976603321043720.
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The stochastic mechanism of synchronous firing in a population of neurons is studied from the point of view of information geometry. Higher-order interactions of neurons, which cannot be reduced to pairwise correlations, are proved to exist in synchronous firing. In a neuron pool where each neuron fires stochastically, the probability distribution q(r) of the activity r, which is the fraction of firing neurons in the pool, is studied. When q(r) has a widespread distribution, in particular, when q(r) has two peaks, the neurons fire synchronously at one time and are quiescent at other times. The mechanism of generating such a probability distribution is interesting because the activity r is concentrated on its mean value when each neuron fires independently, because of the law of large numbers. Even when pairwise interactions, or third-order interactions, exist, the concentration is not resolved. This shows that higher-order interactions are necessary to generate widespread activity distributions. We analyze a simple model in which neurons receive common overlapping inputs and prove that such a model can have a widespread distribution of activity, generating higher-order stochastic interactions.
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Reichenstein, Irit, Chen Eitan, Sandra Diaz-Garcia, Guy Haim, Iddo Magen, Aviad Siany, Mariah L. Hoye, et al. "Human genetics and neuropathology suggest a link between miR-218 and amyotrophic lateral sclerosis pathophysiology." Science Translational Medicine 11, no. 523 (December 18, 2019): eaav5264. http://dx.doi.org/10.1126/scitranslmed.aav5264.
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Motor neuron–specific microRNA-218 (miR-218) has recently received attention because of its roles in mouse development. However, miR-218 relevance to human motor neuron disease was not yet explored. Here, we demonstrate by neuropathology that miR-218 is abundant in healthy human motor neurons. However, in amyotrophic lateral sclerosis (ALS) motor neurons, miR-218 is down-regulated and its mRNA targets are reciprocally up-regulated (derepressed). We further identify the potassium channel Kv10.1 as a new miR-218 direct target that controls neuronal activity. In addition, we screened thousands of ALS genomes and identified six rare variants in the human miR-218-2 sequence. miR-218 gene variants fail to regulate neuron activity, suggesting the importance of this small endogenous RNA for neuronal robustness. The underlying mechanisms involve inhibition of miR-218 biogenesis and reduced processing by DICER. Therefore, miR-218 activity in motor neurons may be susceptible to failure in human ALS, suggesting that miR-218 may be a potential therapeutic target in motor neuron disease.
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Page, Keri L., Jure Zakotnik, Volker Dürr, and Thomas Matheson. "Motor Control of Aimed Limb Movements in an Insect." Journal of Neurophysiology 99, no. 2 (February 2008): 484–99. http://dx.doi.org/10.1152/jn.00922.2007.
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Limb movements that are aimed toward tactile stimuli of the body provide a powerful paradigm with which to study the transformation of motor activity into context-dependent action. We relate the activity of excitatory motor neurons of the locust femoro-tibial joint to the consequent kinematics of hind leg movements made during aimed scratching. There is posture-dependence of motor neuron activity, which is stronger in large amplitude (putative fast) than in small (putative slow and intermediate) motor neurons. We relate this posture dependency to biomechanical aspects of the musculo-skeletal system and explain the occurrence of passive tibial movements that occur in the absence of agonistic motor activity. There is little recorded co-activation of antagonistic tibial extensor and flexor motor neurons, and there is differential recruitment of proximal and distal flexor motor neurons. Large-amplitude motor neurons are often recruited soon after a switch in joint movement direction. Motor bursts containing large-amplitude spikes exhibit high spike rates of small-amplitude motor neurons. The fast extensor tibiae neuron, when recruited, exhibits a pattern of activity quite different to that seen during kicking, jumping, or righting: there is no co-activation of flexor motor neurons and no full tibial flexion. Changes in femoro-tibial joint angle and angular velocity are most strongly dependent on variations in the number of motor neuron spikes and the duration of motor bursts rather than on firing frequency. Our data demonstrate how aimed scratching movements result from interactions between biomechanical features of the musculo-skeletal system and patterns of motor neuron recruitment.
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Brunn, Dennis E., and Antje Heuer. "Cooperative Mechanisms Between Leg Joints of Carausius morosusII. Motor Neuron Activity and Influence of ConditionalBursting Interneuron." Journal of Neurophysiology 79, no. 6 (June 1, 1998): 2977–85. http://dx.doi.org/10.1152/jn.1998.79.6.2977.
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Brunn, Dennis E. and Antje Heuer. Cooperative mechanisms between leg joints of Carausius morosus. II. Motor neuron activity and influence of conditional bursting interneuron. J. Neurophysiol. 79: 2977–2985, 1998. The activity of the motor neuron pools of the protractor coxae muscle and of the thoracic part of the depressor trochanteris muscle during forward walking in the stick insect was investigated, and a spiking local interneuron, able to produce “endogenous bursting” and innervating both motor neuron pools, was identified. Extracellular recordings of the motor neurons innervating the protractor and the thoracic depressor of front, middle, and rear legs, respectively, were made with oil-hook electrodes from the peripheral nerves nl2c and nl4a while the animals were walking on a styrofoam treadwheel. The corresponding leg movements were registered and phase histograms were created with the software Spike2. Intracellular recordings were made in the neuropile of the metathoracic ganglion with glass electrodes filled with the dye Lucifer yellow. In all three legs measured (front, middle, and rear), both motor neuron pools increased their activity during the swing movement. The increase in the activity of the protractor motor neurons started at the end of the stance ∼100 ms before reaching the posterior extreme position (PEP), and the activity of the large-sized depressor motor neurons increased as soon as the tarsus was lifted at the PEP. A local spiking interneuron was identified that excited both motor neuron pools. In 4 of 23 recordings the interneuron started to burst in synchrony with protractor and thoracic depressor motor neurons. During bursting a depolarizing stimulus reinforced and a hyperpolarizing stimulus inhibited the activity of both motor neuron pools. Thus we conclude that the thoracic part of the depressor trochanteris muscle might be a component of the neuromuscular system that shapes the swing movement. The two proximal joints, subcoxal and coxa-trochanter, connected mechanically via the thoracic part of the depressor trochanteris muscle, are also connected neurally by segmental and intersegmental spiking interneurons (this paper) and by nonspiking local interneurons (see companion paper).
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Barash, S., R. M. Bracewell, L. Fogassi, J. W. Gnadt, and R. A. Andersen. "Saccade-related activity in the lateral intraparietal area. II. Spatial properties." Journal of Neurophysiology 66, no. 3 (September 1, 1991): 1109–24. http://dx.doi.org/10.1152/jn.1991.66.3.1109.
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1. Single-neuron activity was recorded from the inferior parietal lobule (IPL) of Macaca mulatta monkeys while they were performing delayed saccades and related tasks. Temporal characteristics of this activity were presented in the companion paper. Here we focus on the spatial characteristics of the activity. The analysis was based on recordings from 145 neurons. All these neurons were from the lateral intraparietal area (LIP), a recently defined subdivision of the IPL. 2. Delayed saccades were made in eight directions. Direction-tuning curves were calculated for each neuron, during each of the following activity phases that were described in the companion paper: light sensitive (LS), delay-period memory (M), and saccade related (S); the latter further partitioned into presaccadic (Pre-S), saccade coincident (S-Co), and postsaccadic (Post-S). 3. Width and preferred direction were calculated for each direction-tuning curve. We studied the distributions of widths and preferred directions in LIP's neuronal population. In each case we included only neurons that showed clear excitatory activity in the phases in question. 4. Width was defined as the angle over which the response was higher than 50% of its maximal net value. Width distributions were similar for all phases studied. Widths varied widely from neuron to neuron, from very narrow (less than 45 degrees) to very wide (close to 360 degrees). Median widths were approximately 90 degrees in all phases. 5. Preferred-direction distributions were also similar for various phases. All directions were represented in each distribution, but contralateral directions were more frequent (e.g., 69% for S-Co). 6. For each neuron the alignment of the preferred directions of its various phases was determined. Distributions of alignments were calculated (again, phases that were not clearly excitatory were disregarded). On the level of the neuronal population LS, M, and Pre-S were well aligned with each other. S-Co was also aligned with these phases, but less precisely. 7. A set of "narrowly tuned" neurons was selected by imposing a constraint of narrow (width, less than 90 degrees) LS and S-Co direction tuning. In this set of neurons, the LS and S-Co preferred directions were very well aligned (median, 12 degrees). The fraction of narrowly tuned neurons in the population was 40% (25/63). Thus, in a large subpopulation of area LIP, a fairly precise alignment exists between sensory and motor fields. 8. An additional set of 82 area LIP neurons were recorded while the monkey performed delayed saccades to 32 targets located on small, medium, and large imaginary circles.(ABSTRACT TRUNCATED AT 400 WORDS)
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Beal, Eleanor. "Single-neuron activity in epilepsy." Nature Reviews Neurology 7, no. 5 (May 2011): 243. http://dx.doi.org/10.1038/nrneurol.2011.56.
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Norris, B. J., M. J. Coleman, and M. P. Nusbaum. "Pyloric motor pattern modification by a newly identified projection neuron in the crab stomatogastric nervous system." Journal of Neurophysiology 75, no. 1 (January 1, 1996): 97–108. http://dx.doi.org/10.1152/jn.1996.75.1.97.
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1. We have used multiple, simultaneous intra- and extracellular recordings as well as Lucifer yellow dye-fills to identify modulatory commissural neuron 5 (MCN5) and characterize its effects in the stomatogastric nervous system (STNS) of the crab, Cancer borealis. MCN5 has a soma and neuropilar arborization in the commissural ganglion (CoG; Figs. 1 and 2), and it projects through the inferior esophageal nerve (ion) and stomatogastric nerve (stn) to the stomatogastric ganglion (STG; Figs. 1-3). 2. Within the CoGs, MCN5 receives esophageal rhythm-timed excitation and pyloric rhythm-timed inhibition (Fig. 4). Additionally, during the lateral teeth protractor phase of the gastric mill rhythm, the pyloric-timed inhibition of MCN5 is reduced or eliminated. 3. Intracellular stimulation of MCN5 excites the pyloric pacemaker ensemble, including the anterior burster (AB), pyloric dilator (PD), and lateral posterior gastric (LPG) neurons. This produces a faster pyloric rhythm. MCN5 stimulation also inhibits all nonpacemaker pyloric neurons, reducing or eliminating their activity (Figs. 5 and 6A; Tables 1 and 2). After MCN5 stimulation, bursting is enhanced for several cycles in some pyloric neurons when compared with their prestimulus activity (Figs. 5 and 6A; Tables 1 and 2). 4. MCN5 evokes distinct responses from each pyloric pacemaker neuron (Figs. 6-8). The AB and LPG neurons respond with increased activity. The AB response includes the presence of large amplitude excitatory postsynaptic potentials (EPSPs) that contribute to a depolarization of the trough of its rhythmic oscillations (Fig. 6). LPG responds by exhibiting increased activity that prolongs the duration of its burst beyond that of AB and PD (Fig. 7). In contrast, MCN5 stimulation initially produces decreased PD neuron activity, followed by a slight enhancement of each PD burst (Figs. 7 and 8). PD activity is further enhanced after MCN5 stimulation (Figs. 7 and 8). 5. MCN5-elicited action potentials evoke discrete, constant latency inhibitory postsynaptic potentials (IPSPs) in all nonpacemaker pyloric neurons, including the inferior cardiac (IC), lateral pyloric (LP), pyloric (PY), and ventricular dilator (VD) neurons (Fig. 9). MCN5 activity also inhibits these neurons indirectly, via its excitation of the pacemaker neurons. The pyloric pacemaker neurons synaptically inhibit all four nonpacemaker neurons. 6. The increased activity in the VD neuron, after MCN5 stimulation, is not mimicked by either direct hyperpolarization or by synaptically inhibiting VD via another pathway (Fig. 10). The poststimulation increase in IC neuron activity is stronger than that after hyperpolarizing current injection but is comparable with that resulting from stimulation of another inhibitory pathway (Fig. 10). The enhanced PY neuron activity is comparable with that resulting from either direct current injection or synaptic inhibition from another pathway (Fig. 10). 7. MCN5 activity increases the pyloric cycle frequency of both slow (< 1 Hz) and fast (1-2 Hz) rhythms (Fig. 11), and it significantly alters the phase relationships that define this motor pattern (Fig. 12). These phase relationships change again after MCN5 stimulation (Fig. 12). 8. MCN5 acts in concert with the pyloric pacemaker ensemble to elicit a pyloric rhythm that exhibits enhanced pacemaker neuron activity and reduced activity in all nonpacemaker neurons. Additionally, despite their electrical coupling, the three types of pacemaker neurons exhibit distinct responses to MCN5 stimulation. This partially uncouples their normally coactive bursts. The resulting motor pattern is distinct from all previously characterized pyloric rhythms.
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Houweling, Arthur R., Guy Doron, Birgit C. Voigt, Lucas J. Herfst, and Michael Brecht. "Nanostimulation: Manipulation of Single Neuron Activity by Juxtacellular Current Injection." Journal of Neurophysiology 103, no. 3 (March 2010): 1696–704. http://dx.doi.org/10.1152/jn.00421.2009.
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In the mammalian brain, many thousands of single-neuron recording studies have been performed but less than 10 single-cell stimulation studies. This paucity of single-cell stimulation data reflects a lack of easily applicable single-cell stimulation techniques. We provide a detailed description of the procedures involved in nanostimulation, a single-cell stimulation method derived from the juxtacellular labeling technique. Nanostimulation is easy to apply and can be directed to a wide variety of identifiable neurons in anesthetized and awake animals. We describe the recording approach and the parameters of the electric configuration underlying nanostimulation. We use glass pipettes with a DC resistance of 4–7 MΩ. Obtaining the juxtacellular configuration requires a close contact between pipette tip and neuron and is associated with a several-fold increase in resistance to values ≥20 MΩ. The recorded action potential (AP) amplitude grows to ≥2 mV, and neurons can be activated with currents in the nanoampere range—hence the term nanostimulation. While exact AP timing has not been achieved, AP frequency and AP number can be parametrically controlled. We demonstrate that nanostimulation can also be used to selectively inhibit sensory responses in identifiable neurons. Nanostimulation is biophysically similar to electroporation, and based on this assumption, we argue that nanostimulation operates on membranes in the micrometer area directly below the pipette tip, where membrane pores are induced by high transmembrane voltage. There is strong evidence to suggest that nanostimulation selectively activates single neurons and that the evoked effects are cell-specific. Nanostimulation therefore holds great potential for elucidating how single neurons contribute to behavior.
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WANG, LEI, PEI-JI LIANG, PU-MING ZHANG, and YI-HONG QIU. "ADAPTATION-DEPENDENT SYNCHRONIZATION TRANSITIONS AND BURST GENERATIONS IN ELECTRICALLY COUPLED NEURAL NETWORKS." International Journal of Neural Systems 24, no. 08 (November 20, 2014): 1450033. http://dx.doi.org/10.1142/s0129065714500336.
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A typical feature of neurons is their ability to encode neural information dynamically through spike frequency adaptation (SFA). Previous studies of SFA on neuronal synchronization were mainly concentrated on the correlated firing between neuron pairs, while the synchronization of neuron populations in the presence of SFA is still unclear. In this study, the influence of SFA on the population synchronization of neurons was numerically explored in electrically coupled networks, with regular, small-world, and random connectivity, respectively. The simulation results indicate that cross-correlation indices decrease significantly when the neurons have adaptation compared with those of nonadapting neurons, similar to previous experimental observations. However, the synchronous activity of population neurons exhibits a rather complex adaptation-dependent manner. Specifically, synchronization strength of neuron populations changes nonmonotonically, depending on the degree of adaptation. In addition, single neurons in the networks can switch from regular spiking to bursting with the increase of adaptation degree. Furthermore, the connection probability among neurons exhibits significant influence on the population synchronous activity, but has little effect on the burst generation of single neurons. Accordingly, the results may suggest that synchronous activity and burst firing of population neurons are both adaptation-dependent.
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MIFTAHOF, ROUSTEM, and N. R. AKHMADEEV. "COMPUTER SIMULATION OF COTRANSMISSION BY EXCITATORY AMINO ACIDS AND ACETYLCHOLINE IN THE ENTERIC NERVOUS SYSTEM." Journal of Mechanics in Medicine and Biology 07, no. 02 (June 2007): 229–46. http://dx.doi.org/10.1142/s0219519407002261.
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The role of cotransmission by α-amino-3-hydroxy-5-methyl-4-isoxalose propionic acid (AMPA), L-aspartate, N-methyl-D-aspartate (NMDA), and acetylcholine (ACh) as well as the coexpression of AMPA, NMDA, and nicotinic ACh (nACh) receptors on the electrophysiological activity of the primary sensory (AH) and motor (S) neurons of the enteric nervous system are numerically assessed. Results of computer simulations showed that AMPA and L-Asp alone can induce fast action potentials of short duration on AH and S neurons. Costimulation of nACh and AMPA receptors on the soma of the S neuron resulted in periodic spiking activity. A characteristic biphasic response was recorded from the AH neuron after coactivation of AMPA and NMDA receptors. Glutamate alone acting on NMDA receptors caused prolonged depolarization of the AH neuron and failed to depolarize the S neuron. Cojoint stimulation of the AMPA or nACh receptors was required to produce the effect of glutamate. The overall electrical response of neurons to the activation of NMDA receptors was long-term depolarization. Acetylcholine, AMPA, and glutamate acting alone or cojointly enhanced phasic contraction of the longitudinal smooth muscle. Treatment of neurons with AMPA, NMDA, and nACh receptor antagonists revealed intricate properties of the AH and S neurons. Application of MK-801, D-AP5, and CPP reduced the excitability of the AH neuron and totally abolished electrical activity in the S neuron. The information gained into the cotransmission by excitatory amino acids and acetylcholine in the enteric nervous system may be beneficial in the development of novel effective therapeutics to treat diseases associated with altered visceral nociception, i.e. irritable bowel syndrome.
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MacIver, M. Bruce, Helen M. Bronte-Stewart, Jaimie M. Henderson, Richard A. Jaffe, and John G. Brock-Utne. "Human Subthalamic Neuron Spiking Exhibits Subtle Responses to Sedatives." Anesthesiology 115, no. 2 (August 1, 2011): 254–64. http://dx.doi.org/10.1097/aln.0b013e3182217126.
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Background During deep brain stimulation implant surgery, microelectrode recordings are used to map the location of targeted neurons. The effects produced by propofol or remifentanil on discharge activity of subthalamic neurons were studied intraoperatively to determine whether they alter neuronal activity. Methods Microelectrode recordings from 11 neurons, each from individual patients, were discriminated and analyzed before and after administration of either propofol or remifentanil. Subthalamic neurons in rat brain slices were recorded in patch-clamp to investigate cellular level effects. Results Neurons discharged at 42 ± 9 spikes/s (mean ± SD) and showed a common pattern of inhibition that lasted 4.3 ms. Unique discharge profiles were evident for each neuron, seen using joint-interval analysis. Propofol (intravenous bolus 0.3 mg/kg) produced sedation, with minor effects on discharge activity (less than 2.0% change in frequency). A prolongation of recurrent inhibition was evident from joint-interval analysis, and propofol's effect peaked within 2 min, with recovery evident at 10 min. Subthalamic neurons recorded in rat brain slices exhibited inhibitory synaptic currents that were prolonged by propofol (155%) but appeared to lack tonic inhibitory currents. Propofol did not alter membrane potential, membrane resistance, current-evoked discharge, or holding current during voltage clamp. Remifentanil (0.05 mg/kg) had little effect on overall subthalamic neuron discharge activity and did not prolong recurrent inhibition. Conclusions These results help to characterize the circuit properties and feedback inhibition of subthalamic neurons and demonstrate that both propofol and remifentanil produce only minor alterations of subthalamic neuron discharge activity that should not interfere with deep brain stimulation implant surgery.
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Carrasco, Dario I., Mark M. Rich, Qingbo Wang, Timothy C. Cope, and Martin J. Pinter. "Activity-Driven Synaptic and Axonal Degeneration in Canine Motor Neuron Disease." Journal of Neurophysiology 92, no. 2 (August 2004): 1175–81. http://dx.doi.org/10.1152/jn.00157.2004.
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The role of neuronal activity in the pathogenesis of neurodegenerative disease is largely unknown. In this study, we examined the effects of increasing motor neuron activity on the pathogenesis of a canine version of inherited motor neuron disease (hereditary canine spinal muscular atrophy). Activity of motor neurons innervating the ankle extensor muscle medial gastrocnemius (MG) was increased by denervating close synergist muscles. In affected animals, 4 wk of synergist denervation accelerated loss of motor-unit function relative to control muscles and decreased motor axon conduction velocities. Slowing of axon conduction was greatest in the most distal portions of motor axons. Morphological analysis of neuromuscular junctions (NMJs) showed that these functional changes were associated with increased loss of intact innervation and with the appearance of significant motor axon and motor terminal sprouting. These effects were not observed in the MG muscles of age-matched, normal animals with synergist denervation for 5 wk. The results indicate that motor neuron action potential activity is a major contributing factor to the loss of motor-unit function and degeneration in inherited canine motor neuron disease.
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Rouach, Nathalie, Jacques Glowinski, and Christian Giaume. "Activity-Dependent Neuronal Control of Gap-Junctional Communication in Astrocytes." Journal of Cell Biology 149, no. 7 (June 26, 2000): 1513–26. http://dx.doi.org/10.1083/jcb.149.7.1513.
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A typical feature of astrocytes is their high degree of intercellular communication through gap junction channels. Using different models of astrocyte cultures and astrocyte/neuron cocultures, we have demonstrated that neurons upregulate gap-junctional communication and the expression of connexin 43 (Cx43) in astrocytes. The propagation of intercellular calcium waves triggered in astrocytes by mechanical stimulation was also increased in cocultures. This facilitation depends on the age and number of neurons, indicating that the state of neuronal differentiation and neuron density constitute two crucial factors of this interaction. The effects of neurons on astrocytic communication and Cx43 expression were reversed completely after neurotoxic treatments. Moreover, the neuronal facilitation of glial coupling was suppressed, without change in Cx43 expression, after prolonged pharmacological treatments that prevented spontaneous synaptic activity. Altogether, these results demonstrate that neurons exert multiple and differential controls on astrocytic gap-junctional communication. Since astrocytes have been shown to facilitate synaptic efficacy, our findings suggest that neuronal and astrocytic networks interact actively through mutual setting of their respective modes of communication.
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Tryba, Andrew K., and Roy E. Ritzmann. "Multi-Joint Coordination During Walking and Foothold Searching in the Blaberus Cockroach. II. Extensor Motor Neuron Pattern." Journal of Neurophysiology 83, no. 6 (June 1, 2000): 3337–50. http://dx.doi.org/10.1152/jn.2000.83.6.3337.
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In a previous study, we combined joint kinematics and electromyograms (EMGs) to examine the change in the phase relationship of two principal leg joints during walking and searching. In this study, we recorded intracellularly from motor neurons in semi-intact behaving animals to examine mechanisms coordinating extension at these leg joints. In particular, we examined the change in the phase of the coxa-trochanter (CTr) and femur-tibia (FT) joint extension during walking and searching. In doing so, we discovered marked similarities in the activity of CTr and FT joint extensor motor neurons at the onset of extension during searching and at the end of stance during walking. The data suggest that the same interneurons may be involved in coordinating the CTr and FT extensor motor neurons during walking and searching. Previous studies in stick insects have suggested that extensor motor neuron activity during the stance phase of walking results from an increase in tonic excitation of the neuron leading to spiking that is periodically interrupted by centrally generated inhibition. However, the CTr and FT extensor motor neuron activity during walking consists of characteristic phasic modulations in motor neuron frequency within each step cycle. The phasic increases and decreases in extensor EMG frequency during stance are associated with kinematic events (i.e., foot set-down and joint cycle transitions) during walking. Sensory feedback associated with these events might be responsible for phasic modulation of the extensor motor neuron frequency. However, our data rule out the possibility that sensory cues resulting from foot set-down are responsible for a decline in CTr extensor activity that is characteristic of the Blaberusstep cycle. Our data also suggest that both phasic excitation and inhibition contribute to extensor motor neuron activity during the stance phase of walking.
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Gupta, Pallavi, Nandhini Balasubramaniam, Hwan-You Chang, Fan-Gang Tseng, and Tuhin Subhra Santra. "A Single-Neuron: Current Trends and Future Prospects." Cells 9, no. 6 (June 23, 2020): 1528. http://dx.doi.org/10.3390/cells9061528.
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The brain is an intricate network with complex organizational principles facilitating a concerted communication between single-neurons, distinct neuron populations, and remote brain areas. The communication, technically referred to as connectivity, between single-neurons, is the center of many investigations aimed at elucidating pathophysiology, anatomical differences, and structural and functional features. In comparison with bulk analysis, single-neuron analysis can provide precise information about neurons or even sub-neuron level electrophysiology, anatomical differences, pathophysiology, structural and functional features, in addition to their communications with other neurons, and can promote essential information to understand the brain and its activity. This review highlights various single-neuron models and their behaviors, followed by different analysis methods. Again, to elucidate cellular dynamics in terms of electrophysiology at the single-neuron level, we emphasize in detail the role of single-neuron mapping and electrophysiological recording. We also elaborate on the recent development of single-neuron isolation, manipulation, and therapeutic progress using advanced micro/nanofluidic devices, as well as microinjection, electroporation, microelectrode array, optical transfection, optogenetic techniques. Further, the development in the field of artificial intelligence in relation to single-neurons is highlighted. The review concludes with between limitations and future prospects of single-neuron analyses.
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von Wittgenstein, Julia, Fang Zheng, Marie-Theres Wittmann, Elli-Anna Balta, Fulvia Ferrazzi, Iris Schäffner, Benjamin M. Häberle, et al. "Sox11 is an Activity-Regulated Gene with Dentate-Gyrus-Specific Expression Upon General Neural Activation." Cerebral Cortex 30, no. 6 (February 20, 2020): 3731–43. http://dx.doi.org/10.1093/cercor/bhz338.
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Abstract Neuronal activity initiates transcriptional programs that shape long-term changes in plasticity. Although neuron subtypes differ in their plasticity response, most activity-dependent transcription factors (TFs) are broadly expressed across neuron subtypes and brain regions. Thus, how region- and neuronal subtype-specific plasticity are established on the transcriptional level remains poorly understood. We report that in young adult (i.e., 6–8 weeks old) mice, the developmental TF SOX11 is induced in neurons within 6 h either by electroconvulsive stimulation or by exploration of a novel environment. Strikingly, SOX11 induction was restricted to the dentate gyrus (DG) of the hippocampus. In the novel environment paradigm, SOX11 was observed in a subset of c-FOS expressing neurons (ca. 15%); whereas around 75% of SOX11+ DG granule neurons were c-FOS+, indicating that SOX11 was induced in an activity-dependent fashion in a subset of neurons. Environmental enrichment or virus-mediated overexpression of SOX11 enhanced the excitability of DG granule cells and downregulated the expression of different potassium channel subunits, whereas conditional Sox11/4 knock-out mice presented the opposite phenotype. We propose that Sox11 is regulated in an activity-dependent fashion, which is specific to the DG, and speculate that activity-dependent Sox11 expression may participate in the modulation of DG neuron plasticity.
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Israel, Davelene D., Sharone Sheffer-Babila, Carl de Luca, Young-Hwan Jo, Shun Mei Liu, Qiu Xia, Daniel J. Spergel, Siok L. Dun, Nae J. Dun, and Streamson C. Chua. "Effects of Leptin and Melanocortin Signaling Interactions on Pubertal Development and Reproduction." Endocrinology 153, no. 5 (March 9, 2012): 2408–19. http://dx.doi.org/10.1210/en.2011-1822.
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Leptin and melanocortin signaling control ingestive behavior, energy balance, and substrate utilization, but only leptin signaling defects cause hypothalamic hypogonadism and infertility. Although GnRH neurons do not express leptin receptors, leptin influences GnRH neuron activity via regulation of immediate downstream mediators including the neuropeptides neuropeptide Y and the melanocortin agonist and antagonist, α-MSH, agouti-related peptide, respectively. Here we show that modulation of melanocortin signaling in female db/db mice through ablation of agouti-related peptide, or heterozygosity of melanocortin 4 receptor, restores the timing of pubertal onset, fertility, and lactation. Additionally, melanocortin 4 receptor activation increases action potential firing and induces c-Fos expression in GnRH neurons, providing further evidence that melanocortin signaling influences GnRH neuron activity. These studies thus establish melanocortin signaling as an important component in the leptin-mediated regulation of GnRH neuron activity, initiation of puberty and fertility.
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KATORI, YUICHI, ERIC J. LANG, MIHO ONIZUKA, MITSUO KAWATO, and KAZUYUKI AIHARA. "QUANTITATIVE MODELING OF SPATIO-TEMPORAL DYNAMICS OF INFERIOR OLIVE NEURONS WITH A SIMPLE CONDUCTANCE-BASED MODEL." International Journal of Bifurcation and Chaos 20, no. 03 (March 2010): 583–603. http://dx.doi.org/10.1142/s0218127410025909.
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Inferior olive (IO) neurons project to the cerebellum and contribute to motor control. They can show intriguing spatio-temporal dynamics with rhythmic and synchronized spiking. IO neurons are connected to their neighbors via gap junctions to form an electrically coupled network, and so it is considered that this coupling contributes to the characteristic dynamics of this nucleus. Here, we demonstrate that a gap junction-coupled network composed of simple conductance-based model neurons (a simplified version of a Hodgkin–Huxley type neuron) reproduce important aspects of IO activity. The simplified phenomenological model neuron facilitated the analysis of the single cell and network properties of the IO while still quantitatively reproducing the spiking patterns of complex spike activity observed by simultaneous recording in anesthetized rats. The results imply that both intrinsic bistability of each neuron and gap junction coupling among neurons play key roles in the generation of the spatio-temporal dynamics of IO neurons.
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Wright, Nathaniel C., Mahmood S. Hoseini, Tansel Baran Yasar, and Ralf Wessel. "Coupling of synaptic inputs to local cortical activity differs among neurons and adapts after stimulus onset." Journal of Neurophysiology 118, no. 6 (December 1, 2017): 3345–59. http://dx.doi.org/10.1152/jn.00398.2017.
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Cortical activity contributes significantly to the high variability of sensory responses of interconnected pyramidal neurons, which has crucial implications for sensory coding. Yet, largely because of technical limitations of in vivo intracellular recordings, the coupling of a pyramidal neuron’s synaptic inputs to the local cortical activity has evaded full understanding. Here we obtained excitatory synaptic conductance ( g) measurements from putative pyramidal neurons and local field potential (LFP) recordings from adjacent cortical circuits during visual processing in the turtle whole brain ex vivo preparation. We found a range of g-LFP coupling across neurons. Importantly, for a given neuron, g-LFP coupling increased at stimulus onset and then relaxed toward intermediate values during continued visual stimulation. A model network with clustered connectivity and synaptic depression reproduced both the diversity and the dynamics of g-LFP coupling. In conclusion, these results establish a rich dependence of single-neuron responses on anatomical, synaptic, and emergent network properties. NEW & NOTEWORTHY Cortical neurons are strongly influenced by the networks in which they are embedded. To understand sensory processing, we must identify the nature of this influence and its underlying mechanisms. Here we investigate synaptic inputs to cortical neurons, and the nearby local field potential, during visual processing. We find a range of neuron-to-network coupling across cortical neurons. This coupling is dynamically modulated during visual processing via biophysical and emergent network properties.
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Yadav, Smita, Susan H. Younger, Linghua Zhang, Katherine L. Thompson-Peer, Tun Li, Lily Y. Jan, and Yuh Nung Jan. "Glial ensheathment of the somatodendritic compartment regulates sensory neuron structure and activity." Proceedings of the National Academy of Sciences 116, no. 11 (February 25, 2019): 5126–34. http://dx.doi.org/10.1073/pnas.1814456116.
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Sensory neurons perceive environmental cues and are important of organismal survival. Peripheral sensory neurons interact intimately with glial cells. While the function of axonal ensheathment by glia is well studied, less is known about the functional significance of glial interaction with the somatodendritic compartment of neurons. Herein, we show that three distinct glia cell types differentially wrap around the axonal and somatodendritic surface of the polymodal dendritic arborization (da) neuron of the Drosophila peripheral nervous system for detection of thermal, mechanical, and light stimuli. We find that glial cell-specific loss of the chromatin modifier gene dATRX in the subperineurial glial layer leads to selective elimination of somatodendritic glial ensheathment, thus allowing us to investigate the function of such ensheathment. We find that somatodendritic glial ensheathment regulates the morphology of the dendritic arbor, as well as the activity of the sensory neuron, in response to sensory stimuli. Additionally, glial ensheathment of the neuronal soma influences dendritic regeneration after injury.
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Flamm, R. E., and R. M. Harris-Warrick. "Aminergic modulation in lobster stomatogastric ganglion. II. Target neurons of dopamine, octopamine, and serotonin within the pyloric circuit." Journal of Neurophysiology 55, no. 5 (May 1, 1986): 866–81. http://dx.doi.org/10.1152/jn.1986.55.5.866.
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In the preceding paper, we describe how dopamine, octopamine, and serotonin modulate the neural circuit generating a well-described motor pattern, the pyloric rhythm of the stomatogastric ganglion in the spiny lobster, Panulirus interruptus. In this paper, we identify the neurons within the pyloric circuit that are directly affected by each amine. We accomplished this by isolating each pyloric neuron from all known synaptic input, using a combination of Lucifer yellow photoinactivation of presynaptic neurons and pharmacological blockade by pyloric neurotransmitters. Dopamine, octopamine, and serotonin were bath applied to the preparation, and the responses of synaptically isolated neurons were recorded. Each amine had a unique constellation of effects on the neurons of the pyloric circuit. Almost every neuron in the circuit was directly affected by each amine. Dopamine and octopamine modulated every neuron, whereas serotonin affected four of the six cell types. Each amine had multiple effects among pyloric neurons including the induction of endogenous rhythmic bursting activity, initiation or enhancement of tonic firing activity, and inhibition accompanied by hyperpolarization. All three amines induced rhythmic bursting in one neuron (the AB neuron), but the form of the underlying slow-wave membrane-potential oscillations was different with octopamine than with dopamine and serotonin. Our knowledge of the effects of each amine on each pyloric neuron, combined with the extensive knowledge of the synaptic organization of the pyloric circuit, has allowed us to explain qualitatively the major aspects of the unique variants of the pyloric motor rhythm that each amine produces in the synaptically intact circuit.
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Bressloff, P. C., and S. Coombes. "Physics of the Extended Neuron." International Journal of Modern Physics B 11, no. 20 (August 10, 1997): 2343–92. http://dx.doi.org/10.1142/s0217979297001209.
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We review recent work concerning the effects of dendritic structure on single neuron response and the dynamics of neural populations. We highlight a number of concepts and techniques from physics useful in studying the behaviour of the spatially extended neuron. First we show how the single neuron Green's function, which incorporates details concerning the geometry of the dendritic tree, can be determined using the theory of random walks. We then exploit the formal analogy between a neuron with dendritic structure and the tight-binding model of excitations on a disordered lattice to analyse various Dyson-like equations arising from the modelling of synaptic inputs and random synaptic background activity. Finally, we formulate the dynamics of interacting populations of spatially extended neurons in terms of a set of Volterra integro-differential equations whose kernels are the single neuron Green's functions. Linear stability analysis and bifurcation theory are then used to investigate two particular aspects of population dynamics (i) pattern formation in a strongly coupled network of analog neurons and (ii) phase-synchronization in a weakly coupled network of integrate-and-fire neurons.