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1
Alia, Sylvie, Jean Azérad, Marc Janian, Gérard Lévy, and Bernard Pollin. "Substance P dans les neurones sensitifs primaires innervant la pulpe dentaire, chez le cobaye." Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie 321, no. 4 (April 1998): 283–88. http://dx.doi.org/10.1016/s0764-4469(98)80052-8.
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Foisset, F., C. Lehalle, A. Nasri, C. Bourdais, I. Vachier, S. Assou, Q. Muller, et al. "Développement d’un modèle d’épithélium bronchique innervé par des neurones sensitifs à partir de cellules souches pluripotentes induites humaines (iPSCs)." Revue des Maladies Respiratoires 40, no. 2 (February 2023): 111. http://dx.doi.org/10.1016/j.rmr.2022.11.006.
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RIND, F. CLAIRE. "IDENTIFICATION OF DIRECTIONALLY SELECTIVE MOTION-DETECTING NEURONES IN THE LOCUST LOBULA AND THEIR SYNAPTIC CONNECTIONS WITH AN IDENTIFIED DESCENDING NEURONE." Journal of Experimental Biology 149, no. 1 (March 1, 1990): 21–43. http://dx.doi.org/10.1242/jeb.149.1.21.
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The anatomy and physiology of two directionally selective motion-detecting neurones in the locust are described. Both neurones had dendrites in the lobula, and projected to the ipsilateral protocerebrum. Their cell bodies were located on the posterio-dorsal junction of the optic lobe with the protocerebrum. The neurones were sensitive to horizontal motion of a visual stimulus. One neurone, LDSMD(F), had a preferred direction forwards over the ipsilateral eye, and a null direction backwards. The other neurone, LDSMD(B), had a preferred direction backwards over the ipsilateral eye 1. Motion in the preferred direction caused EPSPs and spikes in the LDSMD neurones. Motion in the null direction resulted in IPSPs 2. Both excitatory and inhibitory inputs were derived from the ipsilateral eye 3. The DSMD neurones responded to velocities of movement up to and beyond 270°s−1 4. The response of both LDSMD neurones showed no evidence of adaptation during maintained apparent or real movement 5. There was a delay of 60–80 ms between a single step of apparent movement, either the preferred or the null direction, and the start of the response 6. There was a monosynaptic, excitatory connection between the LDSMD(B) neurone and the protocerebral, descending DSMD neurone (PDDSMD) identified in the preceding paper (Rind, 1990). At resting membrane potential, a single presynaptic spike did not give rise to a spike in the postsynaptic neurone
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Labhart, T. "How polarization-sensitive interneurones of crickets see the polarization pattern of the sky: a field study with an opto-electronic model neurone." Journal of Experimental Biology 202, no. 7 (April 1, 1999): 757–70. http://dx.doi.org/10.1242/jeb.202.7.757.
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Many insects gain directional information from the polarization pattern of the sky. Polarization vision is mediated by the specialized ommatidia of the dorsal rim area of the compound eye, which contains highly polarization-sensitive photoreceptors. In crickets Gryllus campestris, polarized light information conveyed by the dorsal rim ommatidia was found to be processed by polarization-opponent interneurones (POL-neurones). In this study, a field-proof opto-electronic model of a POL-neurone was constructed that implements the physiological properties of cricket POL-neurones as measured by previous electrophysiological experiments in the laboratory. Using this model neurone, both the strength of the celestial polarization signal and the directional information available to POL-neurones were assessed under a variety of meteorological conditions. We show that the polarization signal as experienced by cricket POL-neurones is very robust, both because of the special filtering properties of these neurones (polarization-antagonism, spatial low-pass, monochromacy) and because of the relatively stable e-vector pattern of the sky.
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Truman, J. W., J. De Vente, and E. E. Ball. "Nitric oxide-sensitive guanylate cyclase activity is associated with the maturational phase of neuronal development in insects." Development 122, no. 12 (December 1, 1996): 3949–58. http://dx.doi.org/10.1242/dev.122.12.3949.
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Many developing insect neurones pass through a phase when they respond to nitric oxide (NO) by producing cyclic GMP. Studies on identified grasshopper motoneurones show that this NO sensitivity appears after the growth cone has arrived at its target but before it has started to send out branches. NO sensitivity typically ends as synaptogenesis is nearing completion. Data from interneurones and sensory neurones are also consistent with the hypothesis that NO sensitivity appears as a developing neurone changes from axonal outgrowth to maturation and synaptogenesis. Cyclic GMP likely constitutes part of a retrograde signalling pathway between a neurone and its synaptic partner. NO sensitivity also appears in some mature neurones at times when they may be undergoing synaptic rearrangement. Comparative studies on other insects indicate that the association between an NO-sensitive guanylate cyclase and synaptogenesis is an ancient one, as evidenced by its presence in both ancient and more recently evolved insect groups.
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Labhart, Thomas, Jürgen Petzold, and Hansruedi Helbling. "Spatial integration in polarization-sensitive interneurones of crickets: a survey of evidence, mechanisms and benefits." Journal of Experimental Biology 204, no. 14 (July 15, 2001): 2423–30. http://dx.doi.org/10.1242/jeb.204.14.2423.
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SUMMARY Many insects exploit the polarization pattern of the sky for compass orientation in navigation or cruising-course control. Polarization-sensitive neurones (POL1-neurones) in the polarization vision pathway of the cricket visual system have wide visual fields of approximately 60° diameter, i.e. these neurones integrate information over a large area of the sky. This results from two different mechanisms. (i) Optical integration; polarization vision is mediated by a group of specialized ommatidia at the dorsal rim of the eye. These ommatidia lack screening pigment, contain a wide rhabdom and have poor lens optics. As a result, the angular sensitivity of the polarization-sensitive photoreceptors is very wide (median approximately 20°). (ii) Neural integration; each POL1-neurone receives input from a large number of dorsal rim photoreceptors with diverging optical axes. Spatial integration in POL1-neurones acts as a spatial low-pass filter. It improves the quality of the celestial polarization signal by filtering out cloud-induced local disturbances in the polarization pattern and increases sensitivity.
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Grigorian, Gayane, Bella Harutiunian-Kozak, Anahit Kazarian, Armenui Hekimian, Tigran Markarian, and Julius Kozak. "Spatial summation processes in visually driven neurones of cat's pretectal region." Acta Neurobiologiae Experimentalis 54, no. 4 (December 31, 1994): 321–33. http://dx.doi.org/10.55782/ane-1994-1039.
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The spatial summation processes of single neurones of cat's pretectal region were investigated with moving and stationary visual stimuli. The results indicate that the majority of the investigated neurones changed their responses essentially at the gradual increase of size of the applied stimuli (i.e. showed negative or positive summation). Particularly, direction non-sensitive neurones showed symmetrical changes of spatial summation curves in response to two opposite directions of movement. By contrast, in some direction sensitive neurones different characteristics of responses for the two opposite directions of movement were observed. Thus the number of discharges in the responses to the preferred direction could increase or decrease at the gradual increase of the moving stimulus size, while the responses to the null direction could remain stable or vice versa. The same was observed for the "ON" and "OFF" responses in the ON-OFF neurones. Thus, it appears that the pattern of responses of a given neurone to different directions of movement and to the "on" and "off" periods of stationary stimulation are shaped by independent mechanisms.
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Siegelbaum, S. A., F. Belardetti, J. S. Camardo, and M. J. Shuster. "Modulation of the serotonin-sensitive potassium channel in Aplysia sensory neurone cell body and growth cone." Journal of Experimental Biology 124, no. 1 (September 1, 1986): 287–306. http://dx.doi.org/10.1242/jeb.124.1.287.
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Using single-channel recording, we have been able to obtain some insight into the molecular mechanism of a modulatory transmitter action in Aplysia sensory neurones. Our results show that serotonin produces a slow EPSP and increases action potential duration in the sensory neurones by producing prolonged closures of the S potassium channel. Such closures appear to be mediated by cyclic AMP-dependent phosphorylation of a membrane protein which may be the channel. Modulation of S channels by serotonin also occurs in sensory neurone growth cones. This provides the first direct evidence that channel modulation occurs in nerve processes and increases the likelihood of channel modulation at the nerve terminal.
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Calabrese, B., and M. Pellegrino. "Remodelling of an intact neurone in the central nervous system of the leech." Journal of Experimental Biology 198, no. 9 (September 1, 1995): 1989–94. http://dx.doi.org/10.1242/jeb.198.9.1989.
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The regeneration pattern of two identified central neurones was studied in the leech Hirudo medicinalis. Anterior pagoda (AP) and mechanosensory touch-sensitive (T) neurones were stained in adult segmental ganglia, maintained in culture for 6-10 days. AP neurones, which normally project only to the contralateral nerve roots, sprouted extensively in all the available nerve paths during regeneration. Mechanosensory T cells, in the same experimental conditions, showed only a moderate growth and did not change their normal pattern of axonal projections. The observed differences in the growth pattern might account for the different electrophysiological responses to axotomy exhibited by the two types of neurone. Interruption of interganglionic connectives induced a moderate and stereotyped remodelling of the morphology of intact AP neurones, which was reminiscent of that transiently exhibited during embryonic development. This response was observed in 25% of the AP neurones we examined.
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Lundstrom, Brian Nils, Sungho Hong, Matthew H. Higgs, and Adrienne L. Fairhall. "Two Computational Regimes of a Single-Compartment Neuron Separated by a Planar Boundary in Conductance Space." Neural Computation 20, no. 5 (May 2008): 1239–60. http://dx.doi.org/10.1162/neco.2007.05-07-536.
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Recent in vitro data show that neurons respond to input variance with varying sensitivities. Here we demonstrate that Hodgkin-Huxley (HH) neurons can operate in two computational regimes: one that is more sensitive to input variance (differentiating) and one that is less sensitive (integrating). A boundary plane in the 3D conductance space separates these two regimes. For a reduced HH model, this plane can be derived analytically from the V nullcline, thus suggesting a means of relating biophysical parameters to neural computation by analyzing the neuron's dynamical system.
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HERTEL, HORST, and ULRIKE MARONDE. "The Physiology and Morphology of Centrally Projecting Visual Interneurones in the Honeybee Brain." Journal of Experimental Biology 133, no. 1 (November 1, 1987): 301–15. http://dx.doi.org/10.1242/jeb.133.1.301.
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Visual interneurones with projections into the median protocerebrum of the honeybee brain were characterized by electrophysiological and neuroanatomical methods. Extrinsic medulla neurones with wide ramifications in the medulla and terminations in the median posterior protocerebrum show spatial opponency in their tonic responses to stationary light. Wide-field lobula neurones projecting into the dorsal lobe code the direction of movement of visual stimuli by changing the sign of their tonic response. Lobula neurones, with two branches ipsi- and contralateral to the oesophagus, are binocularly sensitive. A moving stimulus in either direction causes excitation or inhibition of these neurones, the sign of the response being dependent on the side of stimulation. The presumed dendrites of an extrinsic lobula neurone, showing combined spectral and spatial opponency, differ markedly in shape from those of lobula movement-detecting neurones. Neurones that connect the optic tubercle with the contralateral dorsal lobe are characterized. They show a non-directionally selective movement sensitivity within a binocular receptive field. Note: Present address: B A M, FG 5.1; Unter den Eichen 87, D-1000 Berlin 45, FRG.
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Buckingham, S., B. Lapied, H. Corronc, and F. Sattelle. "Imidacloprid actions on insect neuronal acetylcholine receptors." Journal of Experimental Biology 200, no. 21 (November 1, 1997): 2685–92. http://dx.doi.org/10.1242/jeb.200.21.2685.
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The neonicotinoid insecticide Imidacloprid acts at three pharmacologically distinct acetylcholine receptor (AChR) subtypes in the cockroach (Periplaneta americana) nervous system, but is ineffective on muscarinic receptors. Imidacloprid (3-100µmoll-1) induced dose-dependent depolarizations at cockroach cercal afferent/giant interneurone synapses. These responses were insensitive to 20µmoll-1 atropine but were completely blocked by the nicotinic antagonist mecamylamine (50µmoll-1). Similarly, Imidacloprid-induced depolarizations of cultured cockroach dorsal unpaired median (DUM) neurones dissociated from the same (terminal abdominal) ganglion were also completely blocked by 100µmoll-1 mecamylamine. However, two components of the response could be distinguished on the basis of their differential sensitivities to 0.1µmoll-1-bungarotoxin (-BTX), which selectively blocks AChRs with 'mixed' nicotinic/muscarinic pharmacology in this preparation. This indicates that Imidacloprid affects both AChRs sensitive to -BTX and -BTX-insensitive nicotinic acetylcholine receptors (nAChRs). Thus, in the cockroach, Imidacloprid activates -BTX-sensitive synaptic nAChRs in giant interneurones, -BTX-insensitive extrasynaptic nAChRs in DUM neurones, and a recently characterized DUM neurone 'mixed' AChR that is sensitive to both nicotinic and muscarinic ligands. Imidacloprid does not act on muscarinic acetylcholine receptors (mAChRs) present on DUM neurone cell bodies and at the cercal afferent/giant interneurone synapses. This study shows that Imidacloprid can act on pharmacologically diverse nAChR subtypes.
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STUMPNER, ANDREAS, and BERNHARD RONACHER. "Auditory Interneurones in the Metathoracic Ganglion of the Grasshopper Chorthippus Biguttulus: I. Morphological and Physiological Characterization." Journal of Experimental Biology 158, no. 1 (July 1, 1991): 391–410. http://dx.doi.org/10.1242/jeb.158.1.391.
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1. Auditory intemeurones originating in the metathoracic ganglion of females of the grasshopper Chorthippus biguttulus can be classified as local (SN), bisegmental (BSN), T-shaped (TN) and ascending neurones (AN). A comparison of branching patterns and physiological properties indicates that auditory interneurones of C. biguttulus are homologous with those described for the locust. 2. Eighteen types of auditory neurones are morphologically characterized on the basis of Lucifer Yellow staining. All of them branch bilaterally in the metathoracic ganglion. Smooth dendrites, from which postsynaptic potentials (PSPs) can be recorded, predominate on the side ipsilateral to the soma. If ‘beaded’ branches exist, they predominate contralaterally. The ascending axon runs contralaterally to the soma, except in T-fibres. 3. Auditory receptors respond tonically. The dynamic range of their intensity-response curve covers 20–25 dB. Local, bisegmental and T-shaped neurones are most sensitive to stimulation ipsilateral to the soma. The responses of SN1 and TNI to white-noise stimuli are similar to those of receptors, while phasic-tonic responses are found in SN4, SN5, SN7 and BSN1. The bisegmental neurones receive side-dependent inhibition that corresponds to a 20–30dB attenuation. One local element (SN6) is predominantly inhibited by acoustic stimuli. 4. Ascending neurones are more sensitive to contralateral stimulation (i.e. on their axon side). Only one of them (AN6) responds tonically to white-noise stimuli at all intensities; others exhibit a tonic discharge only at low or at high intensities.One neurone (AN12) responds with a phasic burst over a wide intensity range. The most directional neurones (AN1, AN2) are excited by contralateral stimuli and (predominantly) inhibited by ipsilateral stimuli. Three ascending neurones (AN13-AN15) are spontaneously active and are inhibited by acoustic stimuli. 5. All auditory intemeurones, except SN5, are more sensitive to pure tones below 10 kHz than to ultrasound.
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Bott, C. J., C. G. Johnson, C. C. Yap, N. D. Dwyer, K. A. Litwa, and B. Winckler. "Nestin in immature embryonic neurons affects axon growth cone morphology and Semaphorin3a sensitivity." Molecular Biology of the Cell 30, no. 10 (May 2019): 1214–29. http://dx.doi.org/10.1091/mbc.e18-06-0361.
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Correct wiring in the neocortex requires that responses to an individual guidance cue vary among neurons in the same location, and within the same neuron over time. Nestin is an atypical intermediate filament expressed strongly in neural progenitors and is thus used widely as a progenitor marker. Here we show a subpopulation of embryonic cortical neurons that transiently express nestin in their axons. Nestin expression is thus not restricted to neural progenitors, but persists for 2–3 d at lower levels in newborn neurons. We found that nestin-expressing neurons have smaller growth cones, suggesting that nestin affects cytoskeletal dynamics. Nestin, unlike other intermediate filament subtypes, regulates cdk5 kinase by binding the cdk5 activator p35. Cdk5 activity is induced by the repulsive guidance cue Semaphorin3a (Sema3a), leading to axonal growth cone collapse in vitro. Therefore, we tested whether nestin-expressing neurons showed altered responses to Sema3a. We find that nestin-expressing newborn neurons are more sensitive to Sema3a in a roscovitine-sensitive manner, whereas nestin knockdown results in lowered sensitivity to Sema3a. We propose that nestin functions in immature neurons to modulate cdk5 downstream of the Sema3a response. Thus, the transient expression of nestin could allow temporal and/or spatial modulation of a neuron’s response to Sema3a, particularly during early axon guidance.
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Simmons, P. "The transfer of signals from photoreceptor cells to large second-order neurones in the ocellar visual system of the locust Locusta migratoria." Journal of Experimental Biology 198, no. 2 (February 1, 1995): 537–49. http://dx.doi.org/10.1242/jeb.198.2.537.
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The operation of the first synapse in the ocellar pathway of the locust Locusta migratoria has been studied by making simultaneous intracellular recordings from photoreceptors and large, second-order L-neurones. 1. The transfer curve for the synapse, obtained by plotting the amplitudes of the initial peak responses by the two cells to pulses of light against each other, shows that L-neurones are extremely sensitive to changes in photoreceptor potential and that the connection is tonically active in darkness. 2. Postsynaptic current in an L-neurone, produced when pulses of light are delivered from a dark background, saturates at a slightly brighter light intensity than does the postsynaptic potential. 3. The signal-to-noise ratio improves with increases in light intensity in both cells, but the reduction in noise as signals are transmitted from photoreceptors to L-neurones is less than would be expected from the number of photoreceptors that probably converge on each L-neurone. 4. In both cells, in the presence of different intensities of background illumination, the slope of the intensity­response curve is maintained as the curve moves along the light intensity axis. Adaptation is relatively slow so that, at least for several minutes after an increase in background illumination, both cells maintain a sustained response and the responses to stimuli of increased illumination are reduced in amplitude. During sustained background illumination, the transfer curve for the synapse between a photoreceptor and an L-neurone shifts along both axes without a change in its maximum slope. 5. The slope of the synaptic transfer curve depends on the speed as well as the amplitude of changes in light. 6. In response to injection of depolarising pulses of current into a photoreceptor, an L-neurone generates brief, hyperpolarising responses. The amplitude of the responses depends on the strength and speed of the depolarising stimuli. After an initial response by an L-neurone, subsequent responses are reduced in amplitude for 200 ms. 7. The amplitude of L-neurone responses to electrical stimulation of a photoreceptor increases when the hyperpolarising constant current is injected into the photoreceptor.
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Grolleau, F., and B. Lapied. "Dorsal unpaired median neurones in the insect central nervous system: towards a better understanding of the ionic mechanisms underlying spontaneous electrical activity." Journal of Experimental Biology 203, no. 11 (June 1, 2000): 1633–48. http://dx.doi.org/10.1242/jeb.203.11.1633.
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The efferent dorsal unpaired median (DUM) neurones, which include octopaminergic neurones, are among the most intensively studied neurones in the insect central nervous system. They differ from other insect neurones in generating endogenous spontaneous overshooting action potentials. The second half of the 1980s is certain to be considered a turning point in the study of the ion channels underlying the electrical activity of DUM neurones. Recent advances made using the patch-clamp technique have stimulated an increasing interest in the understanding of the biophysical properties of both voltage-dependent and voltage-independent ion channels. Patch-clamp studies of DUM neurones in cell culture demonstrate that these neurones express a wide variety of ion channels. At least five different types of K(+) channel have been identified: inward rectifier, delayed rectifier and A-like channels as well as Ca(2+)- and Na(+)-activated K(+) channels. Moreover, besides voltage-dependent Na(+) and Ca(2+)-sensitive Cl(−) channels, DUM neurones also express four types of Ca(2+) channel distinguished on the basis of their kinetics, voltage range of activation and pharmacological profile. Finally, two distinct resting Ca(2+) and Na(+) channels have been shown to be involved in maintaining the membrane potential and in regulating the firing pattern. In this review, we have also attempted critically to evaluate these existing ion channels with regard to their specific functions in the generation of the different phases of the spontaneous electrical activity of the DUM neurone.
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Ruff, Douglas A., and Richard T. Born. "Feature attention for binocular disparity in primate area MT depends on tuning strength." Journal of Neurophysiology 113, no. 5 (March 1, 2015): 1545–55. http://dx.doi.org/10.1152/jn.00772.2014.
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Attending to a stimulus modulates the responses of sensory neurons that represent features of that stimulus, a phenomenon named “feature attention.” For example, attending to a stimulus containing upward motion enhances the responses of upward-preferring direction-selective neurons in the middle temporal area (MT) and suppresses the responses of downward-preferring neurons, even when the attended stimulus is outside of the spatial receptive fields of the recorded neurons (Treue S, Martinez-Trujillo JC. Nature 399: 575–579, 1999). This modulation renders the representation of sensory information across a neuronal population more selective for the features present in the attended stimulus (Martinez-Trujillo JC, Treue S. Curr Biol 14: 744–751, 2004). We hypothesized that if feature attention modulates neurons according to their tuning preferences, it should also be sensitive to their tuning strength, which is the magnitude of the difference in responses to preferred and null stimuli. We measured how the effects of feature attention on MT neurons in rhesus monkeys ( Macaca mulatta) depended on the relationship between features—in our case, direction of motion and binocular disparity—of the attended stimulus and a neuron's tuning for those features. We found that, as for direction, attention to stimuli containing binocular disparity cues modulated the responses of MT neurons and that the magnitude of the modulation depended on both a neuron's tuning preferences and its tuning strength. Our results suggest that modulation by feature attention may depend not just on which features a neuron represents but also on how well the neuron represents those features.
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Wu, Ziniu, Harold Rockwell, Yimeng Zhang, Shiming Tang, and Tai Sing Lee. "Complexity and diversity in sparse code priors improve receptive field characterization of Macaque V1 neurons." PLOS Computational Biology 17, no. 10 (October 25, 2021): e1009528. http://dx.doi.org/10.1371/journal.pcbi.1009528.
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System identification techniques—projection pursuit regression models (PPRs) and convolutional neural networks (CNNs)—provide state-of-the-art performance in predicting visual cortical neurons’ responses to arbitrary input stimuli. However, the constituent kernels recovered by these methods are often noisy and lack coherent structure, making it difficult to understand the underlying component features of a neuron’s receptive field. In this paper, we show that using a dictionary of diverse kernels with complex shapes learned from natural scenes based on efficient coding theory, as the front-end for PPRs and CNNs can improve their performance in neuronal response prediction as well as algorithmic data efficiency and convergence speed. Extensive experimental results also indicate that these sparse-code kernels provide important information on the component features of a neuron’s receptive field. In addition, we find that models with the complex-shaped sparse code front-end are significantly better than models with a standard orientation-selective Gabor filter front-end for modeling V1 neurons that have been found to exhibit complex pattern selectivity. We show that the relative performance difference due to these two front-ends can be used to produce a sensitive metric for detecting complex selectivity in V1 neurons.
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Watanabe, Masayuki, Hiroki Tanaka, Takanori Uka, and Ichiro Fujita. "Disparity-Selective Neurons in Area V4 of Macaque Monkeys." Journal of Neurophysiology 87, no. 4 (April 1, 2002): 1960–73. http://dx.doi.org/10.1152/jn.00780.2000.
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Area V4 is an intermediate stage of the ventral visual pathway providing major input to the final stages in the inferior temporal cortex (IT). This pathway is involved in the processing of shape, color, and texture. IT neurons are also sensitive to horizontal binocular disparity, suggesting that binocular disparity is processed along the ventral visual pathway. In the present study, we examined the processing of binocular disparity information by V4 neurons. We recorded responses of V4 neurons to binocularly disparate stimuli. A population of V4 neurons modified their responses according to changes of stimulus disparity; neither monocular responses nor eye movements could account for this modulation. Disparity-tuning curves were similar for different locations within a neuron's receptive field. Neighboring neurons recorded using a single electrode displayed similar disparity-tuning properties. These findings indicate that a population of V4 neurons is selective for binocular disparity, invariant for the position of the stimulus within the receptive field. The finding that V4 neurons with similar disparity selectivity are clustered suggests the existence of functional modules for disparity processing in V4.
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Matheson, T. "Octopamine modulates the responses and presynaptic inhibition of proprioceptive sensory neurones in the locust Schistocerca gregaria." Journal of Experimental Biology 200, no. 9 (January 1, 1997): 1317–25. http://dx.doi.org/10.1242/jeb.200.9.1317.
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A multineuronal proprioceptor, the femoral chordotonal organ (feCO), monitors the position and movements of the tibia of an insect leg. Superfusing the locust metathoracic feCO with the neuromodulator octopamine, or the octopamine agonist synephrine, affects the position (tonic) component of the organ's response, but not the movement (phasic) component. Both octopamine and synephrine act with the same threshold (10(-6) mol l-1). Individual sensory neurones that respond tonically at flexed tibial angles show increased tonic spike activity following application of octopamine, but those that respond at extended angles do not. Tonic spiking of phaso-tonic flexion-sensitive neurones is enhanced but their phasic spiking is unaffected. Bath application of octopamine to the feCO increases the tonic component of presynaptic inhibition recorded in the sensory terminals, but not the phasic component. This inhibition should at least partially counteract the increased sensory spiking and reduce its effect on postsynaptic targets such as motor neurones. Furthermore, some phasic sensory neurones whose spiking is not affected by octopamine nevertheless show enhanced tonic synaptic inputs. The chordotonal organ is not known to be under direct efferent control, but its output is modified by octopamine acting on its sensory neurones to alter their responsiveness to mechanical stimuli and by presynaptic inhibition acting on their central branches. The effects of this neuromodulator acting peripherally on sensory neurones are therefore further complicated by indirect interactions between the sensory neurones within the central nervous system. Increases of sensory neurone spiking caused by neuromodulators may not necessarily lead to parallel increases in the responses of postsynaptic target neurones.
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Gabbiani, Fabrizio, and Holger G. Krapp. "Spike-Frequency Adaptation and Intrinsic Properties of an Identified, Looming-Sensitive Neuron." Journal of Neurophysiology 96, no. 6 (December 2006): 2951–62. http://dx.doi.org/10.1152/jn.00075.2006.
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We investigated in vivo the characteristics of spike-frequency adaptation and the intrinsic membrane properties of an identified, looming-sensitive interneuron of the locust optic lobe, the lobula giant movement detector (LGMD). The LGMD had an input resistance of 4–5 MΩ, a membrane time constant of about 8 ms, and exhibited inward rectification and rebound spiking after hyperpolarizing current pulses. Responses to depolarizing current pulses revealed the neuron's intrinsic bursting properties and pronounced spike-frequency adaptation. The characteristics of adaptation, including its time course, the attenuation of the firing rate, the mutual dependency of these two variables, and their dependency on injected current, closely followed the predictions of a model first proposed to describe the adaptation of cat visual cortex pyramidal neurons in vivo. Our results thus validate the model in an entirely different context and suggest that it might be applicable to a wide variety of neurons across species. Spike-frequency adaptation is likely to play an important role in tuning the LGMD and in shaping the variability of its responses to visual looming stimuli.
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Fitzpatrick, D. C., S. Kuwada, R. Batra, and C. Trahiotis. "Neural responses to simple simulated echoes in the auditory brain stem of the unanesthetized rabbit." Journal of Neurophysiology 74, no. 6 (December 1, 1995): 2469–86. http://dx.doi.org/10.1152/jn.1995.74.6.2469.
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1. In most natural environments, sound waves from a single source will reach a listener through both direct and reflected paths. Sound traveling the direct path arrives first, and determines the perceived location of the source despite the presence of reflections from many different locations. This phenomenon is called the "law of the first wavefront" or "precedence effect." The time at which the reflection is first perceived as a separately localizable sound defines the end of the precedence window and is called "echo threshold." The precedence effect represents an important property of the auditory system, the neural basis for which has only recently begun to be examined. Here we report the responses of single neurons in the inferior colliculus (IC) and superior olivary complex (SOC) of the unanesthetized rabbit to a sound and its simulated reflection. 2. Stimuli were pairs of monaural or binaural clicks delivered through earphones. The leading click, or conditioner, simulated a direct sound, and the lagging click, or probe, simulated a reflection. Interaural time differences (ITDs) were introduced in the binaural conditioners and probes to adjust their simulated locations. The probe was always set at the neuron's best ITD, whereas the conditioner was set at the neuron's best ITD or its worst ITD. To measure the time course of the effects of the conditioner on the probe, we examined the response to the probe as a function of the conditioner-probe interval (CPI). 3. When IC neurons were tested with conditioners and probes set at the neuron's best ITD, the response to the probe as a function of CPI had one of two forms: early-low or early-high. In early-low neurons the response to the probe was initially suppressed but recovered monotonically at longer CPIs. Early-high neurons showed a nonmonotonic recovery pattern. In these neurons the maximal suppression did not occur at the shortest CPIs, but rather after a period of less suppression. Beyond this point, recovery was similar to that of early-low neurons. The presence of early-high neurons meant that the overall population was never entirely suppressed, even at short CPIs. Taken as a whole. CPIs for 50% recovery of the response to the probe among neurons ranged from 1 to 64 ms with a median of approximately 6 ms. 4. The above results are consistent with the time course of the precedence effect for the following reasons. 1) The lack of complete suppression at any CPI is compatible with behavioral results that show the presence of a probe can be detected even at short CPIs when it is not separately localizable. 2) At a CPI corresponding to echo threshold for human listeners (approximately 4 ms CPI) there was a considerable response to the probe, consistent with it being heard as a separately localizable sound at this CPI. 3) Full recovery for all neurons required a period much longer than that associated with the precedence effect. This is consistent with the relatively long time required for conditioners and probes to be heard with equal loudness. 5. Conditioners with either the best ITD or worst ITD were used to determine the effect of ITD on the response to the probe. The relative amounts of suppression caused by the two ITDs varied among neurons. Some neurons were suppressed about equally by both types of conditioners, others were suppressed more by a conditioner with the best ITD, and still others by a conditioner with the worst ITD. Because the best ITD and worst ITD presumably activate different pathways, these results suggest that different neurons receive a different balance of inhibition from different sources. 6. The recovery functions of neurons not sensitive to ITDs were similar to those of ITD-sensitive, neurons. This suggests that the time course of suppression may be common among different IC populations. 7. We also studied neurons in the SOC. Although many showed binaural interactions, none were sensitive to ITDs. Thus the response of this population may not be
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Robinson, Jane. "Prenatal programming of the female reproductive neuroendocrine system by androgens." Reproduction 132, no. 4 (October 2006): 539–47. http://dx.doi.org/10.1530/rep.1.00064.
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It has been clear for several decades that the areas of the brain that control reproductive function are sexually dimorphic and that the ‘programming actions’ of the male gonadal steroids are responsible for sex-specific release of the gonadotrophins from the pituitary gland. The administration of exogenous steroids to fetal/neonatal animals has pinpointed windows of time in an animals’ development when the reproductive neuroendocrine axis is responsive to the organisational influences of androgens. These ‘critical’ periods for sexual differentiation of the brain are trait- and species-specific. The neural network regulating the activity of the gonadotrophin releasing hormone (GnRH) neurones is vital to the control of reproductive function. It appears that early exposure to androgens does not influence the migratory pathway of the GnRH neurone from the olfactory placode or the size of the population of neurones that colonise the postnatal hypothalamus. However, androgens do influence the number and the nature of connections that these neurones make with other neural phenotypes. Gonadal steroid hormones play key roles in the regulation of GnRH release acting largely via steroid-sensitive intermediary neurones that impinge on the GnRH cells. Certain populations of hormonally responsive neurones have been identified that are sexually dimorphic and project from hypothalamic areas known to be involved in the regulation of GnRH release. These neurones are excellent candidates for the programming actions of male hormones in the reproductive neuroendocrine axis of the developing female.
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Dogas, Z., M. Krolo, E. A. Stuth, M. Tonkovic-Capin, F. A. Hopp, D. R. McCrimmon, and E. J. Zuperku. "Differential Effects of GABAA Receptor Antagonists in the Control of Respiratory Neuronal Discharge Patterns." Journal of Neurophysiology 80, no. 5 (November 1, 1998): 2368–77. http://dx.doi.org/10.1152/jn.1998.80.5.2368.
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Dogas, Z., M. Krolo, E. A. Stuth, M. Tonkovic-Capin, F. A. Hopp, D. R. McCrimmon, and E. J. Zuperku. Differential effects of GABAA receptor antagonists in the control of respiratory neuronal discharge patterns. J. Neurophysiol. 80: 2368–2377, 1998. To ascertain the role of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) in shaping and controlling the phasic discharge patterns of medullary respiratory premotor neurons, localized pressure applications of the competitive GABAA receptor antagonist bicuculline (BIC) and the noncompetitive GABAA receptor antagonist picrotoxin (PIC) were studied. Multibarrel micropipettes were used in halothane anesthetized, paralyzed, ventilated, vagotomized dogs to record single unit activity from inspiratory and expiratory neurons in the caudal ventral respiratory group and to picoeject GABAA receptor antagonists. The moving time average of phrenic nerve activity was used to determine respiratory phase durations and to synchronize cycle-triggered histograms of discharge patterns. Picoejection of BIC and PIC had qualitatively different effects on the discharge patterns of respiratory neurons. BIC caused an increase in the discharge rate during the neuron's active phase without inducing activity during the neuron's normally silent phase. The resulting discharge patterns were amplified replicas (×2–3) of the underlying preejection phasic patterns. In contrast, picoejection of PIC did not increase the peak discharge rate during the neuron's active phase but induced a tonic level of activity during the neuron's normally silent phase. The maximum effective BIC dose (15 ± 1.8 pmol/min) was considerably smaller than that for PIC (280 ± 53 pmol/min). These findings suggest that GABAA receptors with differential pharmacology mediate distinct functions within the same neuron, 1) gain modulation that is BIC sensitive but PIC insensitive and 2) silent-phase inhibition blocked by PIC. These studies also suggest that the choice of an antagonist is an important consideration in the determination of GABA receptor function within the respiratory motor control system.
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Dean, J. B., and J. A. Boulant. "Delayed firing rate responses to temperature in diencephalic slices." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 263, no. 3 (September 1, 1992): R679—R684. http://dx.doi.org/10.1152/ajpregu.1992.263.3.r679.
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Thermoregulatory responses may be delayed in onset and offset by several minutes after changes in hypothalamic temperature. Our preceding study found neurons that displayed delayed firing rate responses during clamped thermal stimulation in remote regions of rat diencephalic tissue slices. The present study looked for similar delayed firing rate responses during clamped (1.5-10 min) changes in each neuron's local temperature. Of 26 neurons tested with clamped thermal stimulation, six (i.e., 23%) showed delayed responses, with on-latencies of 1.0-7.8 min. These neurons rarely showed off-latencies, and the delayed response was not eliminated by synaptic blockade. The on-latencies and ranges of local thermosensitivity were similar to delayed neuronal responses to remote temperature; however, remote-sensitive neurons displayed off-latencies, higher firing rates at 37 degrees C, and greater sensitivity to thermal stimulation. Our findings suggest that delayed thermosensitivity is an intrinsic property of certain neurons and may initiate more elaborate or prolonged delayed responses in synaptically connected diencephalic networks. These networks could explain the delayed thermoregulatory responses observed during hypothalamic thermal stimulation.
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Lemon, Christian H., David M. Wilson, and Susan M. Brasser. "Differential neural representation of oral ethanol by central taste-sensitive neurons in ethanol-preferring and genetically heterogeneous rats." Journal of Neurophysiology 106, no. 6 (December 2011): 3145–56. http://dx.doi.org/10.1152/jn.00580.2011.
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In randomly bred rats, orally applied ethanol stimulates neural substrates for appetitive sweet taste. To study associations between ethanol's oral sensory characteristics and genetically mediated ethanol preference, we made electrophysiological recordings of oral responses (spike density) by taste-sensitive nucleus tractus solitarii neurons in anesthetized selectively bred ethanol-preferring (P) rats and their genetically heterogeneous Wistar (W) control strain. Stimuli (25 total) included ethanol [3%, 5%, 10%, 15%, 25%, and 40% (vol/vol)], a sucrose series (0.01, 0.03, 0.1, 0.3, 0.5, and 1 M), and other sweet, salt, acidic, and bitter stimuli; 50 P and 39 W neurons were sampled. k-means clustering applied to the sucrose response series identified cells showing high (S1) or relatively low (S0) sensitivity to sucrose. A three-way factorial analysis revealed that activity to ethanol was influenced by a neuron's sensitivity to sucrose, ethanol concentration, and rat line ( P = 0.01). Ethanol produced concentration-dependent responses in S1 neurons that were larger than those in S0 cells. Although responses to ethanol by S1 cells did not differ between lines, neuronal firing rates to ethanol in S0 cells increased across concentration only in P rats. Correlation and multivariate analyses revealed that ethanol evoked responses in W neurons that were strongly and selectively associated with activity to sweet stimuli, whereas responses to ethanol by P neurons were not easily associated with activity to representative sweet, sodium salt, acidic, or bitter stimuli. These findings show differential central neural representation of oral ethanol between genetically heterogeneous rats and P rats genetically selected to prefer alcohol.
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Chiquet, M., and J. G. Nicholls. "Neurite outgrowth and synapse formation by identified leech neurones in culture." Journal of Experimental Biology 132, no. 1 (September 1, 1987): 191–206. http://dx.doi.org/10.1242/jeb.132.1.191.
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After injury, neurones in the central nervous system (CNS) of the leech regenerate with a high degree of specificity. The aim of our experiments has been to study the sequential steps involved in neurite growth and synapse formation using isolated identified neurones in culture. An important requirement for sprouting of leech neurones is the substrate. Neurites grow only slowly and sparsely on polylysine or vertebrate laminin. The extracellular matrix of leech ganglion capsules contains a protease-sensitive factor which can be extracted with urea. With this material as substrate, growth proceeds rapidly in defined medium. Another neurite-promoting substrate is provided by the plant lectin concanavalin A (Con A). The activity of Con A, but not of the capsule matrix factor, is blocked by the Con A-specific hapten methyl alpha-D-mannoside. The morphology and branching pattern of the neurites in culture depend on the specific substrate and on the type of neurone. During stimulation, less Ca2+ uptake occurs into growth cones than in cell bodies. The mechanism of neurite growth seems not to depend on activity-mediated Ca2+ influx or on interactions between neuronal cell surfaces. However, even without profuse outgrowth, electrical and chemical synapses develop between neighbouring neurones. The type of synapse depends predictably on the types of neurones within the cell pair. Since the development of a synapse can be followed with time in culture, the sequential events can each be studied separately for this multi-step process.
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Flight, Monica Hoyos. "Stroke-sensitive neurons uncovered." Nature Reviews Neuroscience 14, no. 3 (February 13, 2013): 156. http://dx.doi.org/10.1038/nrn3460.
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Wiemann, Martin, Robert E. Baker, Udo Bonnet, and Dieter Bingmann. "CO2-sensitive medullary neurons." NeuroReport 9, no. 1 (January 1998): 167–70. http://dx.doi.org/10.1097/00001756-199801050-00034.
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Soffe, S. R., and K. T. Sillar. "Patterns of synaptic drive to ventrally located spinal neurones in Rana temporaria embryos during rhythmic and non-rhythmic motor responses." Journal of Experimental Biology 156, no. 1 (March 1, 1991): 101–18. http://dx.doi.org/10.1242/jeb.156.1.101.
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1. Intracellular recordings have been made from ventrally located neurones in the spinal cord of Rana temporaria embryos at around the time of hatching. Both short-latency ‘reflex’ and more prolonged rhythmic motor responses can be elicited by stimulation of the skin in immobilized embryos. Initial responses to single-sided skin stimuli usually involve excitation of neurones on the opposite side and strychnine-sensitive inhibition of neurones on the same side. Less reliable responses to dimming the lights also involve initial excitation on one side associated with inhibition on the opposite side. 2. Intracellular recordings from single neurones during rhythmic activity show that on each cycle the same neurone can fire one or many spikes during the course of a single evoked or spontaneous episode. Bursts occur at longer cycle periods, generally at the start of episodes; single spikes occur at shorter cycle periods, generally later in episodes. 3. During sustained rhythmic responses, neuronal membrane potential is generally depolarised and returns gradually to its resting level at the end of the episode. During the episode, relatively depolarising phases of synaptic excitation alternate with relatively hyperpolarising phases of chloride-dependent synaptic inhibition. Cell input resistance is reduced by around 50% throughout each episode. Within each cycle, input resistance is reduced further during the hyperpolarising phase than during the depolarising phase. 4. Rhythmic excitation and inhibition of ventrally located neurones appears to be similar throughout the whole range of cycle periods, supporting the suggestion that a single rhythm-generating system with a wide ‘permissive’ range drives rhythmic movements in R. temporaria embryos.
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Zhu, Weiguo, Sam M. Galoyan, Jeffrey C. Petruska, Gerry S. Oxford, and Lorne M. Mendell. "A Developmental Switch in Acute Sensitization of Small Dorsal Root Ganglion (DRG) Neurons to Capsaicin or Noxious Heating by NGF." Journal of Neurophysiology 92, no. 5 (November 2004): 3148–52. http://dx.doi.org/10.1152/jn.00356.2004.
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Using dissociated rat dorsal root ganglion (DRG) neurons, we have explored the ability of nerve growth factor (NGF) to acutely (within minutes) sensitize responses of nociceptors to capsaicin or noxious heat during postnatal development. While robust sensitization of noxious heat or capsaicin responses by NGF is observed in adult DRG neurons, responses to such stimuli in trkA-positive neurons from early postnatal animals are not sensitized by NGF. Neurons acquire sensitivity to the hyperalgesic effects of NGF between postnatal days 4 and 10 (P4–P10). In contrast to NGF, bradykinin sensitizes responses to noxious heat in both adult and neonatal DRG neurons. These observations suggest a developmental switch in signal transduction cascades linking trkA receptors to hyperalgesia during postnatal development and differences in the signaling pathways mediating bradykinin- and NGF-induced sensitization.
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SONG, YUNING, and CURTIS L. BAKER. "Neural mechanisms mediating responses to abutting gratings: Luminance edgesvs.illusory contours." Visual Neuroscience 23, no. 2 (March 2006): 181–99. http://dx.doi.org/10.1017/s0952523806232036.
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The discontinuities of phase-shifted abutting line gratings give rise to perception of an “illusory contour” (IC) along the line terminations. Neuronal responses to such ICs have been interpreted as evidence for a specialized visual mechanism, since such responses cannot be predicted from conventional linear receptive fields. However, when the spatial scale of the component gratings (carriers) is large compared to the neuron's luminance passband, these IC responses might be evoked simply by the luminance edges at the line terminations. Thus by presenting abutting gratings at a series of carrier spatial scales to cat A18 neurons, we were able to distinguish genuine nonlinear responses from those due to luminance edges. Around half of the neurons (both simple and complex types) showed a bimodal response pattern to abutting gratings: one peak at a low carrier spatial frequency range that overlapped with the luminance passband, and a second distinct peak at much higher frequencies beyond the neuron's grating resolution. For those bimodally responding neurons, the low-frequency responses were sensitive to carrier phase, but the high-frequency responses were phase-invariant. Thus the responses at low carrier spatial frequencies could be understoodviaa linear model, while the higher frequency responses represented genuine nonlinear IC processing. IC responsive neurons also demonstrated somewhat lower spatial preference to the periodic contours (envelopes) compared to gratings, but the optimal orientation and motion direction for both were quite similar. The nonlinear responses to ICs could be explained by the same energy mechanism underlying responses to second-order stimuli such as contrast-modulated gratings. Similar neuronal preferences for ICs and for gratings may contribute to the form-cue invariant perception of moving contours.
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Mander, P., and G. C. Brown. "Nitric oxide, hypoxia and brain inflammation." Biochemical Society Transactions 32, no. 6 (October 26, 2004): 1068–69. http://dx.doi.org/10.1042/bst0321068.
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NO (nitric oxide) acutely and potently inhibits mitochondrial cytochrome oxidase in competition with oxygen, thereby raising the apparent KM for oxygen of mitochondria and neurons into the physiological or pathological range. We find that NO from an NO donor or glial inducible NOS (nitric oxide synthase) highly sensitizes neurons to hypoxia-induced death, probably via the NO–oxygen competition at cytochrome oxidase. Thus the NO from neuronal NOS during excitotoxicity or the NO from inducible NOS during inflammation may sensitize the brain to hypoxic/ischaemic damage.
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Richmond, J. E., L. R. Funte, W. L. Smith, D. A. Price, and P. G. Haydon. "Activation of a peptidergic synapse locally modulates postsynaptic calcium influx." Journal of Experimental Biology 161, no. 1 (November 1, 1991): 257–71. http://dx.doi.org/10.1242/jeb.161.1.257.
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We examined the synaptic connection between Phe-Met-Arg-Phe-NH2 (FMRFamide)-immunoreactive neurone VD4 and its target neurone P1, both found in the central nervous system of the pond snail Helisoma trivolvis. The major FMRFamide-like peak in neurone VD4 appears to be FMRFamide itself, based on its high performance liquid chromatography (HPLC) elution time and immunoreactivity before and after oxidation, but small peaks are also present at the elution times of Phe-Leu-Arg-Phe-NH2 (FLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide). The modulatory actions of the neuropeptides found in neurone VD4 were tested on the postsynaptic target cell P1. Bath application of both the tetrapeptides FMRFamide and FLRFamide at a concentration of 10(−5) mol l-1 reduced the macroscopic voltage-sensitive calcium current of neurone P1 in culture; FMRFamide by 45% and FLRFamide by 51%. Bath application of the heptapeptide GDPFLRFamide (10(−5) mol l-1) reduced the calcium current by only 8%. We reconstructed the synaptic connection between VD4 and P1 in culture. Action-potential-evoked calcium transients in neurites growing from P1 cells in culture were monitored using Fura-2. Addition of FMRFamide, FLRFamide or GDPFLRFamide reduced the magnitude of the calcium transient in P1. Stimulation of VD4 mimicked the effects of peptide application and caused localized reductions in the action-potential-evoked calcium transients in P1 at the points of contact between the neurites of neurones VD4 and P1. These results suggest that neurone VD4 modulates the calcium influx of neurone P1 through the release of endogenous FMRFamide-related peptides and that this modulatory action is restricted to sites of synaptic interaction.
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Siveke, Ida, Christian Leibold, and Benedikt Grothe. "Spectral Composition of Concurrent Noise Affects Neuronal Sensitivity to Interaural Time Differences of Tones in the Dorsal Nucleus of the Lateral Lemniscus." Journal of Neurophysiology 98, no. 5 (November 2007): 2705–15. http://dx.doi.org/10.1152/jn.00275.2007.
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We are regularly exposed to several concurrent sounds, producing a mixture of binaural cues. The neuronal mechanisms underlying the localization of concurrent sounds are not well understood. The major binaural cues for localizing low-frequency sounds in the horizontal plane are interaural time differences (ITDs). Auditory brain stem neurons encode ITDs by firing maximally in response to “favorable” ITDs and weakly or not at all in response to “unfavorable” ITDs. We recorded from ITD-sensitive neurons in the dorsal nucleus of the lateral lemniscus (DNLL) while presenting pure tones at different ITDs embedded in noise. We found that increasing levels of concurrent white noise suppressed the maximal response rate to tones with favorable ITDs and slightly enhanced the response rate to tones with unfavorable ITDs. Nevertheless, most of the neurons maintained ITD sensitivity to tones even for noise intensities equal to that of the tone. Using concurrent noise with a spectral composition in which the neuron's excitatory frequencies are omitted reduced the maximal response similar to that obtained with concurrent white noise. This finding indicates that the decrease of the maximal rate is mediated by suppressive cross-frequency interactions, which we also observed during monaural stimulation with additional white noise. In contrast, the enhancement of the firing rate to tones at unfavorable ITD might be due to early binaural interactions (e.g., at the level of the superior olive). A simple simulation corroborates this interpretation. Taken together, these findings suggest that the spectral composition of a concurrent sound strongly influences the spatial processing of ITD-sensitive DNLL neurons.
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Yap, Li-Peng, Jerome V. Garcia, Derick S. Han, and Enrique Cadenas. "Role of nitric oxide-mediated glutathionylation in neuronal function: potential regulation of energy utilization." Biochemical Journal 428, no. 1 (April 28, 2010): 85–93. http://dx.doi.org/10.1042/bj20100164.
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Excessive generation of nitric oxide radical (NO•) in neuroinflammation, excitotoxicity and during age-related neurodegenerative disorders entails the localized and concerted increase in nitric oxide synthase(s) expression in glial cells and neurons. The aim of the present study was to assess the biological significance of the impact of NO• on the cell's thiol status with emphasis on S-glutathionylation of targeted proteins. Exposure of primary cortical neurons or astrocytes to increasing flow rates of NO• (0.061–0.25 μM/s) resulted in the following. (i) A decrease in GSH (glutathione) in neurons accompanied by formation of GSNO (S-nitrosoglutathione) and GSSG (glutathione disulfide); neurons were far more sensitive to NO• exposure than astrocytes. (ii) A dose-dependent oxidation of the cellular redox status: the neuron's redox potential increased ~42 mV and that of astrocytes ~23 mV. A good correlation was observed between cell viability and the cellular redox potential. The higher susceptibility of neurons to NO• can be partly explained by a reduced capacity to recover GSH through lower activities of GSNO and GSSG reductases. (iii) S-glutathionylation of a small subset of proteins, among them GAPDH (glyceraldehyde-3-phosphate dehydrogenase), the S-glutathionylation of which resulted in inhibition of enzyme activity. The quantitative analyses of changes in the cell's thiol potential upon NO• exposure and their consequences for S-glutathionylation are discussed in terms of the distinct redox environment of astrocytes and neurons.
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Zhang, Huiming, and Jack B. Kelly. "Responses of Neurons in the Rat's Ventral Nucleus of the Lateral Lemniscus to Amplitude-Modulated Tones." Journal of Neurophysiology 96, no. 6 (December 2006): 2905–14. http://dx.doi.org/10.1152/jn.00481.2006.
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Recordings were made from single neurons in the rat's ventral nucleus of the lateral lemniscus (VNLL) to determine responses to amplitude-modulated (AM) tones. The neurons were first characterized on the basis of their response to tone bursts presented to the contralateral ear and a distinction was made between those with transient onset responses and those with sustained responses. Sinusoidal AM tones were then presented to the contralateral ear with a carrier that matched the neuron's characteristic frequency (CF). Modulation transfer functions were generated on the basis of firing rate (MTFFR) and vector strength (MTFVS). Ninety-two percent of onset neurons that responded continuously to AM tones had band-pass MTFFRs with best modulation frequencies from 10 to 300 Hz. Fifty-four percent of sustained neurons had band-pass MTFFRs with best modulation frequencies from 10 to 500 Hz; other neurons had band-suppressed, all-pass, low-pass, or high-pass functions. Most neurons showed either band-pass or low-pass MTFVS. Responses were well synchronized to the modulation cycle with maximum vector strengths ranging from 0.37 to 0.98 for sustained neurons and 0.78 to 0.99 for onset neurons. The upper frequency limit for response synchrony was higher than that reported for inferior colliculus, but lower than that seen in more peripheral structures. Results suggest that VNLL neurons, especially those with onset responses to tone bursts, are sensitive to temporal features of sounds and narrowly tuned to different modulation rates. However, there was no evidence of a topographic relation between dorsoventral position along the length of VNLL and best modulation frequency as determined by either firing rate or vector strength.
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Larkin, Marilynn. "Sensitive neurons may exacerbate headaches." Lancet 348, no. 9042 (December 1996): 1649. http://dx.doi.org/10.1016/s0140-6736(05)65701-7.
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Aggarwal, Arun. "Handgrip Maximal Voluntary Isometric Contraction Does Not Correlate with Thenar Motor Unit Number Estimation." Neurology Research International 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/187947.
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In slowly progressive conditions, such as motor neurone disease (MND), 50–80% of motor units may be lost before weakness becomes clinically apparent. Despite this, maximal voluntary isometric contraction (MVIC) has been reported as a clinically useful, reliable, and reproducible measure for monitoring disease progression in MND. We performed a study on a group of asymptomatic subjects that showed a lack of correlation between isometric grip strength and thenar MUNE. Motor unit number estimation (MUNE) estimates the number of functioning lower motor neurones innervating a muscle or a group of muscles. We used the statistical electrophysiological technique of MUNE to estimate the number of motor units in thenar group of muscles in 69 subjects: 19 asymptomatic Cu, Zn superoxide dismutase 1 (SOD 1) mutation carriers, 34 family controls, and 16 population controls. The Jamar hand dynamometer was used to measure isometric grip strength. This study suggests that MUNE is more sensitive for monitoring disease progression than maximal voluntary isometric contraction (MVIC), as MUNE correlates with the number of functional motor neurones. This supports the observation that patients with substantial chronic denervation can maintain normal muscle twitch tension until 50–80% of motor units are lost and weakness is detectable.
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Alam, M. N., D. McGinty, and R. Szymusiak. "Neuronal discharge of preoptic/anterior hypothalamic thermosensitive neurons: relation to NREM sleep." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 269, no. 5 (November 1, 1995): R1240—R1249. http://dx.doi.org/10.1152/ajpregu.1995.269.5.r1240.
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Thermosensitive neurons of the preoptic/anterior hypothalamic area (POAH) have been implicated in the regulation of non-rapid eye movement (NREM) sleep. We attempted to identify those medial POAH thermosensitive neurons that may be involved in NREM sleep regulation. The thermosensitivity of medial POAH neurons was studied in five freely moving adult cats by local cooling or warming of the medial POAH with a water-perfused thermode. Of 308 neurons, 65 (21%) were classified as thermosensitive, including 31 (10%) warm-sensitive and 34 (11%) cold-sensitive neurons. The spontaneous discharge rates of 28 warm-sensitive, 34 cold-sensitive, and 115 randomly selected thermoinsensitive neurons were recorded through one to three sleep-waking cycles. Patterns of spontaneous activity for warm- and cold-sensitive neurons were different. Of 28 warm-sensitive neurons, 18 (64%) exhibited increased discharge rate during NREM sleep compared with waking (NREM/wake, > or = 1.2). This subpopulation of warm-sensitive neurons also exhibited significantly increased thermosensitivity when tested during NREM sleep. Of 34 cold-sensitive neurons, 25 (74%) discharged more slowly during NREM sleep compared with waking (NREM/wake, < or = 0.8). This subpopulation of cold-sensitive neurons exhibited decreased thermosensitivity during NREM sleep. These results are consistent with a hypothesis that the activation of sleep-related warm-sensitive neurons and the deactivation of wake-related cold-sensitive neurons may play a key role in the onset and regulation of NREM sleep.
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Labhart, T. "How polarization-sensitive interneurones of crickets perform at low degrees of polarization." Journal of Experimental Biology 199, no. 7 (July 1, 1996): 1467–75. http://dx.doi.org/10.1242/jeb.199.7.1467.
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In crickets, polarized-light information from the blue sky is processed by polarization-opponent interneurones (POL-neurones). These neurones receive input from the polarization-sensitive blue receptors found in the specialized dorsal rim area of the compound eye. Even under optimal conditions, the degree of polarization d does not exceed 0.75 in the blue region of the spectrum and it is normally much lower. The aim of this study is to assess how POL-neurones perform at low, physiologically relevant degrees of polarization. The spiking activity of POL-neurones is a sinusoidal function of e-vector orientation with a 180 ° period. The modulation amplitude of this function decreases strongly as the degree of polarization decreases. However, our data indicate that POL-neurones can signal e-vector information at d-values as low as 0.05, which would allow the polarization-sensitive system of crickets to exploit polarized light from the sky for orientation even under unfavourable meteorological conditions.
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Keemink, Sander W., Clemens Boucsein, and Mark C. W. van Rossum. "Effects of V1 surround modulation tuning on visual saliency and the tilt illusion." Journal of Neurophysiology 120, no. 3 (September 1, 2018): 942–52. http://dx.doi.org/10.1152/jn.00864.2017.
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Neurons in the primary visual cortex respond to oriented stimuli placed in the center of their receptive field, yet their response is modulated by stimuli outside the receptive field (the surround). Classically, this surround modulation is assumed to be strongest if the orientation of the surround stimulus aligns with the neuron’s preferred orientation, irrespective of the actual center stimulus. This neuron-dependent surround modulation has been used to explain a wide range of psychophysical phenomena, such as biased tilt perception and saliency of stimuli with contrasting orientation. However, several neurophysiological studies have shown that for most neurons surround modulation is instead center dependent: it is strongest if the surround orientation aligns with the center stimulus. As the impact of such center-dependent modulation on the population level is unknown, we examine this using computational models. We find that with neuron-dependent modulation the biases in orientation coding, commonly used to explain the tilt illusion, are larger than psychophysically reported, but disappear with center-dependent modulation. Therefore we suggest that a mixture of the two modulation types is necessary to quantitatively explain the psychophysically observed biases. Next, we find that under center-dependent modulation average population responses are more sensitive to orientation differences between stimuli, which in theory could improve saliency detection. However, this effect depends on the specific saliency model. Overall, our results thus show that center-dependent modulation reduces coding bias, while possibly increasing the sensitivity to salient features. NEW & NOTEWORTHY Neural responses in the primary visual cortex are modulated by stimuli surrounding the receptive field. Most earlier studies assume this modulation depends on the neuron’s tuning properties, but experiments have shown that instead it depends mostly on the stimulus characteristics. We show that this simple change leads to neural coding that is less biased and under some conditions more sensitive to salient features.
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Ichikawa, T. "MOTION-SENSITIVE CELLS: PUTATIVE LARVAL NEURONES INCORPORATED INTO THE OPTIC LOBE OF THE ADULT SWALLOWTAIL BUTTERFLY." Journal of Experimental Biology 195, no. 1 (October 1, 1994): 361–80. http://dx.doi.org/10.1242/jeb.195.1.361.
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Intracellular recordings were made from neurones with large somata situated at the anteromedial edge of the medulla of the swallowtail butterfly Papilio xuthus; the neurones were then filled with Lucifer Yellow. These cells are putative larval visual interneurones incorporated into the adult optic lobe of the butterfly. There are four classes of motion-sensitive neurones. Two have a dendritic arborization in the dorsal half of the medulla and project an axon to the medial protocerebrum or the contralateral medulla. They respond to vertical downward motion with a strong burst of action potentials and their background activities are inhibited by motion in the opposite direction. Variations in position of the dendritic fields suggest that each group of neurones forms a coherent set of cells detecting vertical motion in the dorsal half of the visual field of the eye. The third class of neurones connects the lobula plate to the midbrain and is preferentially sensitive to vertical upward motion. The fourth class of neurones has a dendritic arborization in the lobula. These neurones are tonically excited by a moving grating irrespective of the stimulus orientation and movement direction. The presence of motion-sensitive medulla neurones suggests that the detection of local motion is completed in the distal medulla.
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Kazarian, Anahit, Armenui Hekimian, Bella Harutiunian-Kozak, Gajane Grigorian, Julius Kozak, and Tigran Markarian. "Responses of cat's dorsal hippocampal neurons to moving visual stimuli." Acta Neurobiologiae Experimentalis 55, no. 2 (June 30, 1995): 99–107. http://dx.doi.org/10.55782/ane-1995-1065.
Full textAbstract:
Response properties of visually driven neurones in the cat's hippocampal region were investigated. Out of 688 single cells observed 181 (26%) were visually driven. Ocular dominance was determined for 147 of those cells, 90 of which were driven only by the contralateral eye, 20 were driven exclusively by ipsilateral eye and 37 neurones could be activated by both eyes. Receptive field boundaries were outlined for 157; 152 of those neurones were movement-sensitive, and 125 neurones were sensitive to stationary stimuli. A small group of neurones (13%) showed more pronounced reactions to the vertical direction of motion. Some neurones (22%) revealed sensitivity to the shape and size of the applied visual stimuli. These results confirmed earlier data indicating that visually driven neurones in hippocampal region possess complex properties. They are probably involved in a higher level of visual information processing.
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Albeck, Y., and M. Konishi. "Responses of neurons in the auditory pathway of the barn owl to partially correlated binaural signals." Journal of Neurophysiology 74, no. 4 (October 1, 1995): 1689–700. http://dx.doi.org/10.1152/jn.1995.74.4.1689.
Full textAbstract:
1. Extracellular single-unit recording in anesthetized barn owls was used to study neuronal response to dichotic stimuli of variable binaural correlation (BC). Recordings were made in the output fibers of nucleus laminaris (NL), the anterior division of the ventral lateral lemniscal nucleus (VLVa), the core of the central nucleus of the inferior colliculus (ICcC), the lateral shell of the central nucleus of the inferior colliculus (ICcLS), and the external nucleus of the inferior colliculus (ICx). 2. The response of all neurons sensitive to interaural time difference (ITD) varied with BC. The relationship between BC and impulse number fits a linear, a parabolic, or a ramp model. A linear or parabolic model fits most neurons in low-level nuclei. Higher order neurons in ICx did not respond to noise bursts with strong negative binaural correlation, creating a ramp-like response to BC. 3. A neuron's ability to detect ITD varied as a function of BC. Conversely, a neuron's response to BC changed with ITD. Neurons in NL, VLVa, and ICcC show almost periodic ITD response curves. In these neurons peaks and troughs of ITD response curves diminished as BC decreased, creating a flat ITD response when BC = 0. When BC was set to -1, the most favorable ITD became the least favorable one and vice versa. The ITD response curve of ICx neurons usually has a single dominant peak. The response of those neurons to a negatively correlated noise pair (BC = -1) showed two ITD peaks, flanking the position of the primary peak. 4. The parabolic BC response of NL neurons fits the prediction of the cross-correlation model, assuming half-wave rectification of the sound by the cochlea. Linear response is not predicted by the model. However, the parabolic and the linear neurons probably do not belong to two distinct groups as the difference between them is not statistically significant. Thus, the cross-correlation model provides a good description of the binaural response not only in NL but also in VLVa and ICcC. 5. Almost all ramp neurons occurred in either ICx or ICcLS where neurons are more broadly tuned to frequency than those in the lower nuclei. The synthesis of this response type requires, however, not only the convergence of different frequency channels but also inhibition between different ITD channels. We modeled the ramp response as a three-step process. First, different spectral channels converge to create broad frequency tuning. The response to variation in BC will be linear (or parabolic) because it is a sum of linear (parabolic) responses. Second, the activity in some adjacent ITD channels is subtracted by lateral inhibition. Finally, the result is rectified using a high threshold to avoid negative activity.
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Iceman, Kimberly E., George B. Richerson, and Michael B. Harris. "Medullary serotonin neurons are CO2 sensitive in situ." Journal of Neurophysiology 110, no. 11 (December 1, 2013): 2536–44. http://dx.doi.org/10.1152/jn.00288.2013.
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Brainstem central chemoreceptors are critical to the hypercapnic ventilatory response, but their location and identity are poorly understood. When studied in vitro, serotonin-synthesizing (5-HT) neurons within the rat medullary raphé are intrinsically stimulated by CO2/acidosis. The contributions of these neurons to central chemosensitivity in vivo, however, are controversial. Lacking is documentation of CO2-sensitive 5-HT neurons in intact experimental preparations and understanding of their spatial and proportional distribution. Here we test the hypothesis that 5-HT neurons in the rat medullary raphé are sensitive to arterial hypercapnia. We use extracellular recording and hypercapnic challenge of spontaneously active medullary raphé neurons in the unanesthetized in situ perfused decerebrate brainstem preparation to assess chemosensitivity of individual cells. Juxtacellular labeling of a subset of recorded neurons and subsequent immunohistochemistry for the 5-HT-synthesizing enzyme tryptophan hydroxylase (TPH) identify or exclude this neurotransmitter phenotype in electrophysiologically characterized chemosensitive and insensitive cells. We show that the medullary raphé houses a heterogeneous population, including chemosensitive and insensitive 5-HT neurons. Of 124 recorded cells, 16 cells were juxtacellularly filled, visualized, and immunohistochemically identified as 5-HT synthesizing, based on TPH-immunoreactivity. Forty-four percent of 5-HT cells were CO2 stimulated (increased firing rate with hypercapnia), while 56% were unstimulated. Our results demonstrate that medullary raphé neurons are heterogeneous and clearly include a subset of 5-HT neurons that are excited by arterial hypercapnia. Together with data identifying intrinsically CO2-sensitive 5-HT neurons in vitro, these results support a role for such cells as central chemoreceptors in the intact system.
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MADDESS, T., R. A. DUBOIS, and M. R. IBBOTSON. "Response Properties and Adaptation of Neurones Sensitive to Image Motion in the Butterfly Papilio Aegeus." Journal of Experimental Biology 161, no. 1 (November 1, 1991): 171–99. http://dx.doi.org/10.1242/jeb.161.1.171.
Full textAbstract:
Wide-field direction-selective neurones from the optic lobes of the butterfly Papilio aegeus show some properties similar to those displayed by the large neurones of the fly lobula plate. Temporal and spatial frequency threshold tuning curves show that butterfly optic lobe neurones sensitive to different directions of image motion are fed by presynaptic subunits similar to those of the fly. However, unlike fly lobula plate neurones, the butterfly optic lobe neurones show a steep low-spatial-frequency roll-off which persists even at high temporal frequencies. Also exceptional is the temporal resolution of rapid changes in image speed by the butterfly neurones. When the cells are adapted to continuous motion their responses indicate a further increase in temporal resolution. Evidence is provided that in any one state of adaptation the neurones may be thought of as piece-wise linear and, thus, their responses can be predicted by convolution with a velocity kernel measured for that adaptation state. Adaptation to continuous motion results in the cells responding to motion in proportion to the mean motion signal. Motion in the non-preferred direction also appears to adapt the cells. Velocity impulse responses of both butterfly and blowfly neurones were determined with one-dimensional gratings and two-dimensional textured patterns and the results for the two stimuli are shown to be very similar.
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Burgoon, Penny W., and Jack A. Boulant. "Temperature-sensitive properties of rat suprachiasmatic nucleus neurons." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, no. 3 (September 1, 2001): R706—R715. http://dx.doi.org/10.1152/ajpregu.2001.281.3.r706.
Full textAbstract:
The hypothalamic suprachiasmatic nucleus (SCN) contains a heterogeneous population of neurons, some of which are temperature sensitive in their firing rate activity. Neuronal thermosensitivity may provide cues that synchronize the circadian clock. In addition, through synaptic inhibition on nearby cells, thermosensitive neurons may provide temperature compensation to other SCN neurons, enabling postsynaptic neurons to maintain a constant firing rate despite changes in temperature. To identify mechanisms of neuronal thermosensitivity, whole cell patch recordings monitored resting and transient potentials of SCN neurons in rat hypothalamic tissue slices during changes in temperature. Firing rate temperature sensitivity is not due to thermally dependent changes in the resting membrane potential, action potential threshold, or amplitude of the fast afterhyperpolarizing potential (AHP). The primary mechanism of neuronal thermosensitivity resides in the depolarizing prepotential, which is the slow depolarization that occurs prior to the membrane potential reaching threshold. In thermosensitive neurons, warming increases the prepotential's rate of depolarization, such that threshold is reached sooner. This shortens the interspike interval and increases the firing rate. In some SCN neurons, the slow component of the AHP provides an additional mechanism for thermosensitivity. In these neurons, warming causes the slow AHP to begin at a more depolarized level, and this, in turn, shortens the interspike interval to increase firing rate.
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Silva, N. L., and J. A. Boulant. "Effects of testosterone, estradiol, and temperature on neurons in preoptic tissue slices." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 250, no. 4 (April 1, 1986): R625—R632. http://dx.doi.org/10.1152/ajpregu.1986.250.4.r625.
Full textAbstract:
Thermosensitive preoptic neurons have been implicated in the regulation of body temperature. Testosterone- and estrogen-sensitive preoptic neurons have been implicated in reproductive behavioral and endocrine responses. In this study, rat preoptic tissue slices were used to examine the specificity of these neurons by determining their individual firing rate responses to both temperature and reproductive steroids. Of the 180 neurons classified according to thermosensitivity, 37% were warm sensitive, 8% were cold sensitive, and 55% were temperature insensitive. Ninety-three neurons were tested for their responses to perfusion media containing either testosterone or estradiol (30 pg/ml). Of the cells tested with both steroids, testosterone or estradiol affected half of the thermosensitive neurons and one-third of the temperature-insensitive neurons. This indicates that the population of temperature-insensitive neurons does not contain the majority of the steroid-sensitive neurons. There was much specificity, however, between the two types of steroid-sensitive neurons; testosterone and estradiol rarely affected the same neuron. Although these findings do not indicate a strong specificity between thermosensitive and steroid-sensitive neurons, they do support previous studies suggesting interactions between thermoregulatory and reproductive systems.
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Jiang, M. M., A. Kirchgessner, M. D. Gershon, and A. Surprenant. "Cholera toxin-sensitive neurons in guinea pig submucosal plexus." American Journal of Physiology-Gastrointestinal and Liver Physiology 264, no. 1 (January 1, 1993): G86—G94. http://dx.doi.org/10.1152/ajpgi.1993.264.1.g86.
Full textAbstract:
Cholera toxin (CT) increases intestinal secretions by direct stimulation of mucosal enterocytes; enteric neurons also may play a role. We tested the latter possibility by retrograde labeling of mucosal terminals in guinea pig small intestine with the B subunit of CT (B-CT) and by intracellular recordings from submucosal neurons during superfusion with CT. All vasoactive intestinal peptide (VIP)-positive neurons, and only VIP-positive neurons, were labeled with B-CT. Fluorogold (FG) was used to retrogradely label nerve terminals in submucosal arterioles in preparations in which B-CT labeled mucosal terminals; colocalization of B-CT with FG was observed in neurons up to 3 mm from the site of FG application. CT selectively depolarized neurons known to contain VIP. We conclude that all VIP-containing neurons, and only VIP neurons, in guinea pig submucosal plexus possess B-CT binding sites and can be activated by CT. Some of these neurons provide a dual innervation to both arterioles and mucosa. We suggest that one functional consequence of CT may be to activate vasodilator nerves, thus increasing vascular perfusion of the mucosa to further stimulate intestinal secretions.