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Journal articles on the topic 'Electrode mappings'
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1
Garde, Henrik, and Nuutti Hyvönen. "Mimicking relative continuum measurements by electrode data in two-dimensional electrical impedance tomography." Numerische Mathematik 147, no. 3 (February 15, 2021): 579–609. http://dx.doi.org/10.1007/s00211-020-01170-8.
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AbstractThis paper introduces a constructive method for approximating relative continuum measurements in two-dimensional electrical impedance tomography based on data originating from either the point electrode model or the complete electrode model. The upper bounds for the corresponding approximation errors explicitly depend on the number (and size) of the employed electrodes as well as on the regularity of the continuum current that is mimicked. In particular, if the input current and the object boundary are infinitely smooth, the discrepancy associated with the point electrode model converges to zero faster than any negative power of the number of electrodes. The results are first proven for the unit disk via trigonometric interpolation and quadrature rules, and they are subsequently extended to more general domains with the help of conformal mappings.
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Oproiu, Ana Maria, Ioan Lascar, Octavian Dontu, Catalin Florea, Rodica Scarlet, Ioana Sebe, Lidia Dobrescu, et al. "Topography of the Human Ulnar Nerve for Mounting a Neuro-Prosthesis with Sensory Feedback." Revista de Chimie 69, no. 9 (October 15, 2018): 2494–97. http://dx.doi.org/10.37358/rc.18.9.6561.
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This article presents the performed experimental measurements for connecting a sensory feedback neuro-prosthesis to the peripheral nervous system of a patient with forearm amputation. The experiments focused on the ring finger motion�s neuron control in the forearm prosthesis and on the neural path transmission of the tactile sensation coming from the pressure sensors fitted on the small finger phalanges (F5). For the ring finger, both motor control and sensory feedback are transmitted through the ulnar nerve�s motor axons, respectively by the ulnar nerve�s sensory axons. At the beginning of this study, the topography of the ulnar nerve has been performed, in order to identify the axons by which motor controls are transmitted for the small finger movement (F5) and the axons through which small finger (F5) tactile information is transmitted. A Carl Zeiss S8 electronic microscope was used to analyze the ulnar nerve�s transverse sections for an anonymous patient. Cross sections in the ulnar nerve have been examined, from the tip of the small finger (F5) to the shoulder area. The separately mappings of motor and sensory axons from the ulnar nerve at the wrist�s level and at the elbow�s level were then performed. 3D modeling was performed using CATIA software solution for mapping the axon topography in the ulnar nerve. By means of the ulnar nerve�s 3D topographic map, the optimal place for the implantation of both motor control electrodes and small finger (F5) sensory feedback electrodes were identified in the particular case of a patient with forearm amputation. Subsequently, by surgical procedures, experimental implantation of a motor control electrode for the small finger (F5) from a neuro-prosthesis was performed as well as a sensory feedback electrode for the same finger. For the next two weeks, measurements were made while the patient has been learning to move the small finger (F5) of the neuro-prosthesis and feel the tactile sensation from this finger. After these two weeks the electrodes were extracted from the patient�s stump by surgery.
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Kakemoto, Hirofumi, Jianyong Li, Takakiyo Harigai, Song Min Nam, Satoshi Wada, and Takaaki Tsurumi. "High Frequency Dielectric Permittivity Measurement of Dielectric Layer of MLCC Using Non-Contact Probe." Key Engineering Materials 350 (October 2007): 243–46. http://dx.doi.org/10.4028/www.scientific.net/kem.350.243.
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Direct observations for high frequency microscopic dielectric distributions in cross sections of a multi-layer ceramic capacitor were carried out using non-contact type microwave probe. The measured data were imaged from the raw data and rounding data process. Using microwave reflection intensity mappings from cross sections of multi-layer ceramic capacitor, the dielectric permittivity distribution in micro-region of a multi-layer ceramic capacitor was measured at room temperature. The spatial resolution was experimentally estimated to be about 10 μm from mappings of the dielectric and inner electrode layers in a multi-layer ceramic capacitor.
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Adamatzky, Andrew, Jörg Schnauß, and Florian Huber. "Actin droplet machine." Royal Society Open Science 6, no. 12 (December 2019): 191135. http://dx.doi.org/10.1098/rsos.191135.
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The actin droplet machine is a computer model of a three-dimensional network of actin bundles developed in a droplet of a physiological solution, which implements mappings of sets of binary strings. The actin bundle network is conductive to travelling excitations, i.e. impulses. The machine is interfaced with an arbitrary selected set of k electrodes through which stimuli, binary strings of length k represented by impulses generated on the electrodes, are applied and responses are recorded. The responses are recorded in a form of impulses and then converted to binary strings. The machine’s state is a binary string of length k : if there is an impulse recorded on the i th electrode, there is a ‘1’ in the i th position of the string, and ‘0’ otherwise. We present a design of the machine and analyse its state transition graphs. We envisage that actin droplet machines could form an elementary processor of future massive parallel computers made from biopolymers.
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Rabinowitz, William M., and Donald K. Eddington. "Effects of Channel-to-Electrode Mappings on Speech Reception with the Ineraid Cochlear Implant." Ear and Hearing 16, no. 5 (October 1995): 450–58. http://dx.doi.org/10.1097/00003446-199510000-00002.
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Parker, Jonathon J., Ryan M. Jamiolkowski, Gerald A. Grant, Scheherazade Le, and Casey H. Halpern. "Hybrid Fluoroscopic and Neurophysiological Targeting of Responsive Neurostimulation of the Rolandic Cortex." Operative Neurosurgery 21, no. 3 (June 16, 2021): E180—E186. http://dx.doi.org/10.1093/ons/opab182.
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Abstract BACKGROUND Precise targeting of cortical surface electrodes to epileptogenic regions defined by anatomic and electrophysiological guideposts remains a surgical challenge during implantation of responsive neurostimulation (RNS) devices. OBJECTIVE To describe a hybrid fluoroscopic and neurophysiological technique for targeting of subdural cortical surface electrodes to anatomic regions with limited direct visualization, such as the interhemispheric fissure. METHODS Intraoperative two-dimensional (2D) fluoroscopy was used to colocalize and align an electrode for permanent device implantation with a temporary in Situ electrode placed for extraoperative seizure mapping. Intraoperative phase reversal mapping technique was performed to distinguish primary somatosensory and motor cortex. RESULTS We applied these techniques to optimize placement of an interhemispheric strip electrode connected to a responsive neurostimulator system for detection and treatment of seizures arising from a large perirolandic cortical malformation. Intraoperative neuromonitoring (IONM) phase reversal technique facilitated neuroanatomic mapping and electrode placement. CONCLUSION In challenging-to-access anatomic regions, fluoroscopy and intraoperative neurophysiology can be employed to augment targeting of neuromodulation electrodes to the site of seizure onset zone or specific neurophysiological biomarkers of clinical interest while minimizing brain retraction.
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Carlson, Jonathan Dennis, Kate Elizabeth McLeod, Pamela Sue McLeod, and Jamelynn Brooke Mark. "Stereotactic Accuracy and Surgical Utility of the O-Arm in Deep Brain Stimulation Surgery." Operative Neurosurgery 13, no. 1 (June 27, 2016): 96–107. http://dx.doi.org/10.1227/neu.0000000000001326.
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Abstract BACKGROUND: The stereotactic accuracy of intraoperative imaging is critical to clinical outcome, particularly in “asleep” deep brain stimulation (DBS) surgery that typically forgoes neurophysiological techniques. Different intraoperative imaging modalities and associated accuracies have been reported, including magnetic resonance imaging (MRI), computed tomography (CT), and O-arm. OBJECTIVE: To analyze intraoperative O-arm imaging accuracy and to evaluate the utility of microelectrode mapping. METHODS: O-arm images of DBS electrodes were collected during implantation in the subthalamic nucleus in patients with Parkinson disease. Images were fused to postoperative MRI and postoperative CT scans. Stereotactic coordinates for the electrode tip were measured independently. Radial distances between the images were compared. The impact of microelectrode mapping on final DBS electrode positioning was also evaluated. RESULTS: In 71 consecutive DBS electrodes, the average radial error of the electrode tip between the O-arm and MRI was 1.55 ± 0.58 mm. The average radial error between the O-arm and CT was 1.03 ± 0.61 mm. Thus, the O-arm images accurately depicted the position of the electrode. However, in 14% of cases, microelectrode mapping revised the DBS electrode position beyond the preoperative direct target in combination with accurate intraoperative imaging. CONCLUSION: Intraoperative O-arm images reliably and accurately displayed the location of the DBS electrode compared with postoperative CT and MRI images. Microelectrode mapping provided superior subnuclear resolution to imaging. Both intraoperative imaging and microelectrode mapping are effective tools that can be synergistically combined for optimal DBS electrode placement.
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Bradley, D. C., P. R. Troyk, J. A. Berg, M. Bak, S. Cogan, R. Erickson, C. Kufta, et al. "Visuotopic Mapping Through a Multichannel Stimulating Implant in Primate V1." Journal of Neurophysiology 93, no. 3 (March 2005): 1659–70. http://dx.doi.org/10.1152/jn.01213.2003.
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We report on our efforts to establish an animal model for the development and testing of a cortical visual prostheses. One-hundred-fifty-two electrodes were implanted in the primary visual cortex of a rhesus monkey. The electrodes were made from iridium with an activated iridium oxide film, which has a large charge capacity for a given surface area, and insulated with parylene-C. One-hundred-fourteen electrodes were functional after implantation. The activity of small (2–3) neuronal clusters was first recorded to map the visually responsive region corresponding to each electrode. The animal was then trained in a memory (delayed) saccade task, first with a visual target, then to a target defined by direct cortical stimulation with coordinates specified by the stimulating electrode's mapped receptive field. The SD of saccade endpoints was ∼2.5 larger for electrically stimulated versus visual saccades; nevertheless, when trial-to-trial scatter was averaged out, the correlation between saccade end points and receptive field locations was highly significant and approached unity after several months of training. Five electrodes were left unused until the monkey was fully trained; when these were introduced, the receptive field-saccade correlations were high on the first day of use ( R = 0.85, P = 0.03 for angle, R = 0.98, P < 0.001 for eccentricity), indicating that the monkey had not learned to perform the task empirically by memorizing reward zones. The results of this experiment suggest the potential for rigorous behavioral testing of cortical visual prostheses in the macaque.
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Han, Seunggu Jude, Zoe Teton, Kunal Gupta, Aaron Kawamoto, and Ahmed M. Raslan. "Novel Use of Stimulating Fence-Post Technique for Functional Mapping of Subcortical White Matter During Tumor Resection: A Technical Case Series." Operative Neurosurgery 19, no. 3 (March 4, 2020): 264–70. http://dx.doi.org/10.1093/ons/opaa027.
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Abstract Background Maximal safe resection remains a key principle in infiltrating glioma management. Stimulation mapping is a key adjunct for minimizing functional morbidity while “fence-post” procedures use catheters or dye to mark the tumor border at the start of the procedure prior to brain shift. Objective To report a novel technique using stereotactically placed electrodes to guide tumor resection near critical descending subcortical fibers. Methods Navigated electrodes were placed prior to tumor resection along the deep margin bordering presumed eloquent tracts. Stimulation was administered through these depth electrodes for subcortical motor and language mapping. Results Twelve patients were included in this preliminary technical report. Seven patients (7/12, 58%) were in asleep cases, while the other 5 cases (5/12, 42%) were performed awake. Mapping of motor fibers was performed in 8 cases, and language mapping was done in 1 case. In 3 cases, both motor and language mapping were performed using the same depth electrode spanning corticospinal tract and the arcuate fasciculus. Conclusion Stereotactic depth electrode placement coupled with stimulation mapping of white matter tracts can be used concomitantly to demarcate the border between deep tumor margins and eloquent brain, thus helping to maximize extent of resection while minimizing functional morbidity.
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Fan, Xiaoyao, David W. Roberts, Yasmin Kamal, Jonathan D. Olson, and Keith D. Paulsen. "Quantification of Subdural Electrode Shift Between Initial Implantation, Postimplantation Computed Tomography, and Subsequent Resection Surgery." Operative Neurosurgery 16, no. 1 (March 29, 2018): 9–19. http://dx.doi.org/10.1093/ons/opy050.
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Abstract BACKGROUND Subdural electrodes are often implanted for localization of epileptic regions. Postoperative computed tomography (CT) is typically acquired to locate electrode positions for planning any subsequent surgical resection. Electrodes are assumed to remain stationary between CT acquisition and resection surgery. OBJECTIVE To quantify subdural electrode shift that occurred between the times of implantation (Crani 1), postoperative CT acquisition, and resection surgery (Crani 2). METHODS Twenty-three patients in this case series undergoing subdural electrode implantation were evaluated. Preoperative magnetic resonance and postoperative CT were acquired and coregistered, and electrode positions were extracted from CT. Intraoperative positions of electrodes and the cortical surface were digitized with a coregistered stereovision system. Movement of the exposed cortical surface was also tracked, and change in electrode positions was calculated relative to both the skull and the cortical surface. RESULTS In the 23 cases, average shift of electrode positions was 8.0 ± 3.3 mm between Crani 1 and CT, 9.2 ± 3.7 mm between CT and Crani 2, and 6.2 ± 3.0 mm between Crani 1 and Crani 2. The average cortical shift was 4.7 ± 1.4 mm with 2.9 ± 1.0 mm in the lateral direction. The average shift of electrode positions relative to the cortical surface between Crani 1 and Crani 2 was 5.5 ± 3.7 mm. CONCLUSION The results show that electrodes shifted laterally not only relative to the skull, but also relative to the cortical surface, thereby displacing the electrodes from their initial placement on the cortex. This has significant clinical implications for resection based upon seizure activity and functional mapping derived from intracranial electrodes.
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VAN DEURSEN, A. P. J. "INFLUENCE OF ELECTRODE AND SAMPLE SHAPE ON THE 1/f NOISE PARAMETER fQ: A SCHWARZ-CHRISTOFFEL ANALYSIS." Fluctuation and Noise Letters 10, no. 04 (December 2011): 485–95. http://dx.doi.org/10.1142/s0219477511000697.
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Thin films for material characterization and noise tests are preferentially manufactured with rectangular electrode shapes. In the companying paper Vandamme presents expressions for resistance and geometrical noise factor fQ for the case of circular electrodes. The present paper employs numerical conformal mapping to obtain accurate values for rectangular and circular electrodes. The sample size is either assumed very large, or is taken comparable to the electrodes.
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Pieters, Thomas A., Christopher R. Conner, and Nitin Tandon. "Recursive grid partitioning on a cortical surface model: an optimized technique for the localization of implanted subdural electrodes." Journal of Neurosurgery 118, no. 5 (May 2013): 1086–97. http://dx.doi.org/10.3171/2013.2.jns121450.
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Object Precise localization of subdural electrodes (SDEs) is essential for the interpretation of data from intracranial electrocorticography recordings. Blood and fluid accumulation underneath the craniotomy flap leads to a nonlinear deformation of the brain surface and of the SDE array on postoperative CT scans and adversely impacts the accurate localization of electrodes located underneath the craniotomy. Older methods that localize electrodes based on their identification on a postimplantation CT scan with coregistration to a preimplantation MR image can result in significant problems with accuracy of the electrode localization. The authors report 3 novel methods that rely on the creation of a set of 3D mesh models to depict the pial surface and a smoothed pial envelope. Two of these new methods are designed to localize electrodes, and they are compared with 6 methods currently in use to determine their relative accuracy and reliability. Methods The first method involves manually localizing each electrode using digital photographs obtained at surgery. This is highly accurate, but requires time intensive, operator-dependent input. The second uses 4 electrodes localized manually in conjunction with an automated, recursive partitioning technique to localize the entire electrode array. The authors evaluated the accuracy of previously published methods by applying the methods to their data and comparing them against the photograph-based localization. Finally, the authors further enhanced the usability of these methods by using automatic parcellation techniques to assign anatomical labels to individual electrodes as well as by generating an inflated cortical surface model while still preserving electrode locations relative to the cortical anatomy. Results The recursive grid partitioning had the least error compared with older methods (672 electrodes, 6.4-mm maximum electrode error, 2.0-mm mean error, p < 10−18). The maximum errors derived using prior methods of localization ranged from 8.2 to 11.7 mm for an individual electrode, with mean errors ranging between 2.9 and 4.1 mm depending on the method used. The authors also noted a larger error in all methods that used CT scans alone to localize electrodes compared with those that used both postoperative CT and postoperative MRI. The large mean errors reported with these methods are liable to affect intermodal data comparisons (for example, with functional mapping techniques) and may impact surgical decision making. Conclusions The authors have presented several aspects of using new techniques to visualize electrodes implanted for localizing epilepsy. The ability to use automated labeling schemas to denote which gyrus a particular electrode overlies is potentially of great utility in planning resections and in corroborating the results of extraoperative stimulation mapping. Dilation of the pial mesh model provides, for the first time, a sense of the cortical surface not sampled by the electrode, and the potential roles this “electrophysiologically hidden” cortex may play in both eloquent function and seizure onset.
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Berte, Benjamin, Katja Zeppenfeld, and Roderick Tung. "Impact of Micro-, Mini- and Multi-Electrode Mapping on Ventricular Substrate Characterisation." Arrhythmia & Electrophysiology Review 9, no. 3 (November 5, 2020): 128–35. http://dx.doi.org/10.15420/aer.2020.24.
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Accurate substrate characterisation may improve the evolving understanding and treatment of cardiac arrhythmias. During substrate-based ablation techniques, wide practice variations exist with mapping via dedicated multi-electrode catheter or conventional ablation catheters. Recently, newer ablation catheter technology with embedded mapping electrodes have been introduced. This article focuses on the general misconceptions of voltage mapping and more specific differences in unipolar and bipolar signal morphology, field of view, signal-to-noise ratio, mapping capabilities (density and resolution), catheter-specific voltage thresholds and impact of micro-, mini- and multi-electrodes for substrate mapping. Efficiency and cost-effectiveness of different catheter types are discussed. Increasing sampling density with smaller electrodes allows for higher resolution with a greater likelihood to record near-field electrical information. These advances may help to further improve our mechanistic understanding of the correlation between substrate and ventricular tachycardia, as well as macro-reentry arrhythmia in humans.
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Malkin, Robert A., and Bradford D. Pendley. "Construction of a very high-density extracellular electrode array." American Journal of Physiology-Heart and Circulatory Physiology 279, no. 1 (July 1, 2000): H437—H442. http://dx.doi.org/10.1152/ajpheart.2000.279.1.h437.
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Cellular activation mapping (specifying in time and space the electrical activation sequence of cells) is a well-established basic research tool in cardiac, neural, and gastric physiology. Much recent research in cardiac mapping has focused on large arrays (>200 electrodes) with small electrodes (<500 μm). Construction of such arrays using standard techniques is tedious and yields irregular electrode spacing. We present a novel construction technique that rapidly produces large arrays with regularly spaced small electrodes. For methods, fine-pitch copper ribbon cables, insulated with either polyvinylchloride (PVC) or polyimide (flexible printed circuit; FPC), were assembled together such that the active surface was the cut end of the cable. The cut end was sanded and polished, then coated with silver and sometimes silver chloride. Once completed, the alternating current (AC) root-mean-square (rms) potential was measured between two adjacent, individual electrodes. Polarization testing was conducted according to a previously reported protocol (Witkowski FX and Penkoske PA. J Electrocardiol 21: 273–282, 1988). Activation mapping was conducted in the open-chest guinea pig with both pacing- and defibrillation- strength stimuli. In terms of results, four PVC and three FPC arrays were constructed, ranging from 4 to 400 electrodes. Two hours of labor were needed to create a complete electrode array, independent of the number of electrodes, including connectors and silver/silver chloride coating. As expected, the addition of a silver/silver chloride coating significantly reduced (0.76–0.42 mV, P < 0.001) the AC rms potential difference between two electrodes. A nearly immediate recovery of the potential difference between adjacent pairs of silver/silver chloride electrodes was observed after defibrillation stimuli.
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Kowalczyk, L., H. Goszczynska, E. Zalewska, A. Bajera, and L. Krolicki. "Invisible Base Electrode Coordinates Approximation for Simultaneous SPECT and EEG Data Visualization." Measurement Science Review 14, no. 2 (April 1, 2014): 109–16. http://dx.doi.org/10.2478/msr-2014-0015.
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Abstract This work was performed as part of a larger research concerning the feasibility of improving the localization of epileptic foci, as compared to the standard SPECT examination, by applying the technique of EEG mapping. The presented study extends our previous work on the development of a method for superposition of SPECT images and EEG 3D maps when these two examinations are performed simultaneously. Due to the lack of anatomical data in SPECT images it is a much more difficult task than in the case of MRI/EEG study where electrodes are visible in morphological images. Using the appropriate dose of radioisotope we mark five base electrodes to make them visible in the SPECT image and then approximate the coordinates of the remaining electrodes using properties of the 10-20 electrode placement system and the proposed nine-ellipses model. This allows computing a sequence of 3D EEG maps spanning on all electrodes. It happens, however, that not all five base electrodes can be reliably identified in SPECT data. The aim of the current study was to develop a method for determining the coordinates of base electrode(s) missing in the SPECT image. The algorithm for coordinates approximation has been developed and was tested on data collected for three subjects with all visible electrodes. To increase the accuracy of the approximation we used head surface models. Freely available model from Oostenveld research based on data from SPM package and our own model based on data from our EEG/SPECT studies were used. For data collected in four cases with one electrode not visible we compared the invisible base electrode coordinates approximation for Oostenveld and our models. The results vary depending on the missing electrode placement, but application of the realistic head model significantly increases the accuracy of the approximation.
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Lammers, W. J., A. al-Kais, S. Singh, K. Arafat, and T. Y. el-Sharkawy. "Multielectrode mapping of slow-wave activity in the isolated rabbit duodenum." Journal of Applied Physiology 74, no. 3 (March 1, 1993): 1454–61. http://dx.doi.org/10.1152/jappl.1993.74.3.1454.
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The technique of multiple simultaneous recordings from a large number of extracellular electrodes (> 100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple-electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum, and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first results show that there is a considerable variation in conduction pattern, which is determined by the site of the natural pacemaker. Several experiments were performed to rule out possible deleterious effects of positioning the multiple-electrode assembly on the duodenum. Furthermore, prolonged periods of recording did not influence propagation speed and pattern provided that the positioning of the multiple electrode assembly was performed with care. Entrainment of the natural pacemaker was possible by applying electrical stimuli through 2 of the 240 extracellular electrodes during simultaneous recordings. In conclusion, multisite extracellular mapping of gastrointestinal smooth muscle is possible and can be used to study origin and spread of slow-wave activity.
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Barnett, Gene H., Richard C. Burgess, Issam A. Award, George J. Skipper, Christopher R. Edwards, and Hans Luders. "Epidural Peg Electrodes for the Presurgical Evaluation of Intractable Epilepsy." Neurosurgery 27, no. 1 (July 1, 1990): 113–15. http://dx.doi.org/10.1227/00006123-199007000-00016.
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Abstract A new electrode design for the extradural recording of electrical brain activity is described. Epidural peg electrodes are implantable mushroom-shaped composites of Silastic clastomer and a stainless steel or platinum disc. These electrodes are useful for the preoperative mapping of seizure foci in some patients who have cranial defects or severe muscle artifacts on scalp recordings. They are also used for canvassing wide areas of cortex to determine whether a seizure is focal in origin, arises diffusely from a hemisphere, or has a bilateral origin. Advantages of epidural peg electrodes over screw and other types of epidural electrodes include low risk of infection or hemorrhage and improved patient comfort.
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Pollnow, Stefan, Joachim Greiner, Tobias Oesterlein, Eike M. Wülfers, Axel Loewe, and Olaf Dössel. "Mini Electrodes on Ablation Catheters: Valuable Addition or Redundant Information?—Insights from a Computational Study." Computational and Mathematical Methods in Medicine 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/1686290.
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Radiofrequency ablation has become a first-line approach for curative therapy of many cardiac arrhythmias. Various existing catheter designs provide high spatial resolution to identify the best spot for performing ablation and to assess lesion formation. However, creation of transmural and nonconducting ablation lesions requires usage of catheters with larger electrodes and improved thermal conductivity, leading to reduced spatial sensitivity. As trade-off, an ablation catheter with integrated mini electrodes was introduced. The additional diagnostic benefit of this catheter is still not clear. In order to solve this issue, we implemented a computational setup with different ablation scenarios. Ourin silicoresults show that peak-to-peak amplitudes of unipolar electrograms from mini electrodes are more suitable to differentiate ablated and nonablated tissue compared to electrograms from the distal ablation electrode. However, in orthogonal mapping position, no significant difference was observed between distal electrode and mini electrodes electrograms in the ablation scenarios. In conclusion, catheters with mini electrodes bring about additional benefit to distinguish ablated tissue from nonablated tissue in parallel position with high spatial resolution. It is feasible to detect conduction gaps in linear lesions with this catheter by evaluating electrogram data from mini electrodes.
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HYVÖNEN, NUUTTI. "APPROXIMATING IDEALIZED BOUNDARY DATA OF ELECTRIC IMPEDANCE TOMOGRAPHY BY ELECTRODE MEASUREMENTS." Mathematical Models and Methods in Applied Sciences 19, no. 07 (July 2009): 1185–202. http://dx.doi.org/10.1142/s0218202509003759.
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In electric impedance tomography, one tries to recover the spatial admittance distribution inside a body from boundary measurements of current and voltage. In theoretical considerations, it is usually assumed that the available data is the infinite-dimensional Neumann-to-Dirichlet map, i.e. one assumes to be able to use any boundary current and measure the corresponding potential everywhere on the object boundary. However, in practice, the data consists of a finite-dimensional operator mapping the electrode currents onto the corresponding electrode potentials. What is more, the measurements are affected by the contact impedance at the electrode-object interfaces. In this paper, we show that the introduction of a suitable nonorthogonal projection operator makes it possible to approximate the Neumann-to-Dirichlet map by its electrode counterpart in the topology of bounded linear operators on square integrable functions, with the discrepancy depending linearly on the distance between centers of adjacent electrodes. In particular, convergence is proved without assuming that the electrodes cover all of the object boundary. The theoretical results are complemented by two-dimensional numerical experiments.
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Asch, Ted, and H. Frank Morrison. "Mapping and monitoring electrical resistivity with surface and subsurface electrode arrays." GEOPHYSICS 54, no. 2 (February 1989): 235–44. http://dx.doi.org/10.1190/1.1442647.
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Electrical resistivity measurements using combinations of subsurface and surface electrodes are more sensitive to subsurface inhomogeneities than arrays confined to the surface. A further advantage of the subsurface configuration is that the strong influence of near‐surface inhomogeneities can be reduced by differencing the measured apparent resistivities with a reference set of values obtained with the subsurface electrode(s) at a particular depth. This process accentuates the response of features near the downhole electrode while canceling the response of the near‐surface features. An idealized two‐dimensional model of a nuclear waste repository has been used to demonstrate the effectiveness of this differencing scheme. It is shown that resistivity measurements using borehole electrodes well away from the repository and on the surface are sensitive to changes in the repository that could not be practically observed from surface measurements. This sensitivity is preserved in the presence of a conducting and inhomogeneous surface layer and, most importantly, it is preserved even if the resistivities of the near‐surface features also change.
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Chen, Mengxiao, Zhe Wang, Yu Zheng, Qichong Zhang, Bing He, Jiao Yang, Miao Qi, and Lei Wei. "Flexible Tactile Sensor Based on Patterned Ag-Nanofiber Electrodes through Electrospinning." Sensors 21, no. 7 (March 31, 2021): 2413. http://dx.doi.org/10.3390/s21072413.
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The growing demand for intelligent equipment has greatly inspired the development of flexible devices. Thus, disparate flexible multifunctional devices, including pressure sensitive flexible/stretchable displays, have drawn worldwide research attention. Electrodes maintaining conductivity and mechanical strength against deformations are indispensable components in all prospective applications. In this work, a flexible pressure mapping sensor array is developed based on patterned Ag-nanofibers (Ag-NFs) electrode through electrospinning and lithography. The metallic Ag layer is sputtered onto the electrospinning polyvinyl alcohol (PVA) NFs. A uniform and super conductive electrode layer with outstanding mechanical performance is thus formed after dissolving PVA. Followed by the traditional lithography method, a patterned electrode array (4 × 4 sensors) is obtained. Based on the newly developed triboelectric nanogenerator (TENG) technology, a flexible pressure-mapping sensor with excellent stability towards bending deformations is further demonstrated. Moreover, a letter “Z” is successfully visualized by this pressure sensor array, encouraging more human–machine interactive implementations, such as multi-functional tactile screens.
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Witkowski, F. X., and P. A. Penkoske. "A new fabrication technique for directly coupled transmural cardiac electrodes." American Journal of Physiology-Heart and Circulatory Physiology 254, no. 4 (April 1, 1988): H804—H810. http://dx.doi.org/10.1152/ajpheart.1988.254.4.h804.
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Many current attempts at electrophysiological elucidation of cardiac arrhythmia mechanisms have centered around activation sequence mapping. This is most commonly performed with polarized unipolar or bipolar metal electrodes, which, because of unstable direct current (DC) base-line potentials, necessitate alternating current (AC)-coupled amplification. An ideal nonpolarizable unipolar electrode offers unhindered exchange of charge allowing for stable DC recordings of biological electrical activity. In addition to activation information, DC unipolar recordings enable quantitation of systolic and diastolic potentials, other low-frequency phenomena of interest such as repolarization, as well as rapid recovery from such rapid extreme potential shifts such as defibrillation. Previous attempts to apply nonpolarizable electrodes to transmural cardiac investigations required complex wick electrode techniques to prevent mechanical movement of the fluid-metal interface when chlorided silver wire was used. We have developed a technique to fabricate miniature sintered Ag-AgCl electrodes that are mounted at various locations on a 20-gauge stainless steel needle permitting stable transmural DC unipolar electrogram recordings in vivo. The electrodes are low noise, rugged, sterilizable, and reusable and should prove useful in three-dimensional electrophysiological characterization of the heart.
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DePaoli, Damon, Laurent Goetz, Dave Gagnon, Gabriel Maranon, Michel Prud’homme, Léo Cantin, Martin Parent, and Daniel C. Côté. "Intraoperative fiber optic guidance during chronic electrode implantation in deep brain stimulation neurosurgery: proof of concept in primates." Journal of Neurosurgery 132, no. 6 (June 2020): 1810–19. http://dx.doi.org/10.3171/2019.1.jns182600.
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OBJECTIVEThe clinical outcome of deep brain stimulation (DBS) surgery relies heavily on the implantation accuracy of a chronic stimulating electrode into a small target brain region. Most techniques that have been proposed to precisely target these deep brain regions were designed to map intracerebral electrode trajectory prior to chronic electrode placement, sometimes leading to positioning error of the final electrode. This study was designed to create a new intraoperative guidance tool for DBS neurosurgery that can improve target detection during the final implantation of the chronic electrode.METHODSTaking advantage of diffuse reflectance spectroscopy, the authors developed a new surgical tool that senses proximal brain tissue through the tip of the chronic electrode by means of a novel stylet, which provides rigidity to DBS leads and houses fiber optics.RESULTSAs a proof of concept, the authors demonstrated the ability of their noninvasive optical guidance technique to precisely locate the border of the subthalamic nucleus during the implantation of commercially available DBS electrodes in anesthetized parkinsonian monkeys. Innovative optical recordings combined to standard microelectrode mapping and detailed postmortem brain examination allowed the authors to confirm the precision of optical target detection. They also show the optical technique’s ability to detect, in real time, upcoming blood vessels, reducing the risk of hemorrhage during the chronic lead implantation.CONCLUSIONSThe authors present a new optical guidance technique that can detect target brain regions during DBS surgery from within the implanted electrode using a proof of concept in nonhuman primates. The technique discriminates tissue in real time, contributes no additional invasiveness to the procedure by being housed within the electrode, and can provide complementary information to microelectrode mapping during the implantation of the chronic electrode. The technique may also be a powerful tool for providing direct anatomical information in the case of direct implantations wherein microelectrode mapping is not performed.
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Charroó, Lidia Esther, Sandra Bermejo, Antonio Simeón Paz Cordovez, Carina Rodríguez, Charles C. Finley, and Aniket A. Saoji. "Effect of Number of Electrodes Used to Elicit Electrical Stapedius Reflex Thresholds in Cochlear Implants." Audiology and Neurotology 26, no. 3 (2021): 164–72. http://dx.doi.org/10.1159/000510467.
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<b><i>Introduction:</i></b> When mapping cochlear implant (CI) patients with limited reporting abilities, the lowest electrical stimulus level that produces a stapedial reflex (i.e., the electrical stapedius reflex threshold [eSRT]) can be measured to estimate the upper bound of stimulation on individual or a subset of CI electrodes. However, eSRTs measured for individual electrodes or a subset of electrodes cannot be used to predict the global adjustment of electrical stimulation levels needed to achieve comfortable loudness sensations that can be readily used in a speech coding strategy. In the present study, eSRTs were measured for 1-, 4-, and 15-electrode stimulation to (1) determine changes in eSRT levels as a function of the electrode stimulation mode and (2) determine which stimulation mode eSRT levels best approximate comfortable loudness levels from patients’ clinical maps. <b><i>Methods:</i></b> eSRTs were measured with the 3 different electrical stimulation configurations in 9 CI patients and compared with behaviorally measured, comfortable loudness levels or M-levels from patients’ clinical maps. <b><i>Results:</i></b> A linear, mixed-effects, repeated-measures analysis revealed significant differences (<i>p</i> < 0.01) between eSRTs measured as a function of the stimulation mode. No significant differences (<i>p</i> = 0.059) were measured between 15-electrode eSRTs and M-levels from patients’ clinical maps. The eSRTs measured for 1- and 4-electrode stimulation differed significantly (<i>p</i> < 0.05) from the M-levels on the corresponding electrodes from the patients’ clinical map. <b><i>Conclusion:</i></b> eSRT profiles based on 1- or 4-electrode stimulation can be used to determine comfortable loudness level on either individual or a subset of electrodes, and 15-electrode eSRT profiles can be used to determine the upper bound of electrical stimulation that can be used in a speech coding strategy.
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Pirbadian, Sahand, Marko S. Chavez, and Mohamed Y. El-Naggar. "Spatiotemporal mapping of bacterial membrane potential responses to extracellular electron transfer." Proceedings of the National Academy of Sciences 117, no. 33 (August 3, 2020): 20171–79. http://dx.doi.org/10.1073/pnas.2000802117.
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Extracellular electron transfer (EET) allows microorganisms to gain energy by linking intracellular reactions to external surfaces ranging from natural minerals to the electrodes of bioelectrochemical renewable energy technologies. In the past two decades, electrochemical techniques have been used to investigate EET in a wide range of microbes, with emphasis on dissimilatory metal-reducing bacteria, such asShewanella oneidensisMR-1, as model organisms. However, due to the typically bulk nature of these techniques, they are unable to reveal the subpopulation variation in EET or link the observed electrochemical currents to energy gain by individual cells, thus overlooking the potentially complex spatial patterns of activity in bioelectrochemical systems. Here, to address these limitations, we use the cell membrane potential as a bioenergetic indicator of EET byS. oneidensisMR-1 cells. Using a fluorescent membrane potential indicator during in vivo single-cell-level fluorescence microscopy in a bioelectrochemical reactor, we demonstrate that membrane potential strongly correlates with EET. Increasing electrode potential and associated EET current leads to more negative membrane potential. This EET-induced membrane hyperpolarization is spatially limited to cells in contact with the electrode and within a near-electrode zone (<30 μm) where the hyperpolarization decays with increasing cell-electrode distance. The high spatial and temporal resolution of the reported technique can be used to study the single-cell-level dynamics of EET not only on electrode surfaces, but also during respiration of other solid-phase electron acceptors.
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Coeler, Matthias, Vanessa van Laack, Frederieke Langer, Annegret Potthoff, Sören Höhn, Sebastian Reuber, Katharina Koscheck, and Mareike Wolter. "Infiltrated and Isostatic Laminated NCM and LTO Electrodes with Plastic Crystal Electrolyte Based on Succinonitrile for Lithium-Ion Solid State Batteries." Batteries 7, no. 1 (February 3, 2021): 11. http://dx.doi.org/10.3390/batteries7010011.
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We report a new process technique for electrode manufacturing for all solid-state batteries. Porous electrodes are manufactured by a tape casting process and subsequently infiltrated by a plastic crystal polymer electrolyte (PCPE). With a following isostatic lamination process, the PCPE was further integrated deeply into the porous electrode layer, forming a composite electrode. The PCPE comprises the plastic crystal succinonitrile (SN), lithium conductive salt LiTFSI and polyacrylonitrile (PAN) and exhibits suitable thermal, rheological (ƞ = 0.6 Pa s @ 80 °C 1 s−1) and electrochemical properties (σ > 10−4 S/cm @ 45 °C). We detected a lowered porosity of infiltrated and laminated electrodes through Hg porosimetry, showing a reduction from 25.6% to 2.6% (NCM infiltrated to laminated) and 32.9% to 4.0% (LTO infiltrated to laminated). Infiltration of PCPE into the electrodes was further verified by FESEM images and EDS mapping of sulfur content of the conductive salt. Cycling tests of full cells with NCM and LTO electrodes with PCPE separator at 45 °C showed up to 165 mAh/g at 0.03C over 20 cycles, which is about 97% of the total usable LTO capacity with a coulomb efficiency of between 98 and 99%. Cycling tests at 0.1C showed a capacity of ~128 mAh/g after 40 cycles. The C-rate of 0.2C showed a mean capacity of 127 mAh/g. In summary, we could manufacture full cells using a plastic crystal polymer electrolyte suitable for NCM and LTO active material, which is easily to be integrated into porous electrodes and which is being able to be used in future cell concepts like bipolar stacked cells.
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Ghimire, Purna C., Arjun Bhattarai, Rüdiger Schweiss, Günther G. Scherer, Nyunt Wai, Tuti M. Lim, and Qingyu Yan. "Investigation of Reactant Conversion in the Vanadium Redox Flow Battery Using Spatially Resolved State of Charge Mapping." Batteries 5, no. 1 (January 1, 2019): 2. http://dx.doi.org/10.3390/batteries5010002.
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Segmented cells enable real time visualization of the flow distribution in vanadium redox flow batteries by local current or voltage mapping. The lateral flow of current within thick porous electrodes, however, impairs the local resolution of the detected signals. In this study, the open circuit voltage immediately after the cessation of charge/discharge is used for the mapping of reactant conversion. This quantity is not hampered by lateral flow of current and can be conveniently transformed to the corresponding state of charge. The difference between theoretically calculated and experimentally determined conversion (change in the state of charge) across the electrode is used to determine local variations in conversion efficiency. The method is validated by systematic experiments using electrodes with different modifications, varying current densities and flow configurations. The procedure and the interpretation are simple and scalable to any size of flow cell.
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Ziesche, Ralf F., Anton S. Tremsin, Chun Huang, Chun Tan, Patrick S. Grant, Malte Storm, Dan J. L. Brett, Paul R. Shearing, and Winfried Kockelmann. "4D Bragg Edge Tomography of Directional Ice Templated Graphite Electrodes." Journal of Imaging 6, no. 12 (December 11, 2020): 136. http://dx.doi.org/10.3390/jimaging6120136.
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Bragg edge tomography was carried out on novel, ultra-thick, directional ice templated graphite electrodes for Li-ion battery cells to visualise the distribution of graphite and stable lithiation phases, namely LiC12 and LiC6. The four-dimensional Bragg edge, wavelength-resolved neutron tomography technique allowed the investigation of the crystallographic lithiation states and comparison with the electrode state of charge. The tomographic imaging technique provided insight into the crystallographic changes during de-/lithiation over the electrode thickness by mapping the attenuation curves and Bragg edge parameters with a spatial resolution of approximately 300 µm. This feasibility study was performed on the IMAT beamline at the ISIS pulsed neutron spallation source, UK, and was the first time the 4D Bragg edge tomography method was applied to Li-ion battery electrodes. The utility of the technique was further enhanced by correlation with corresponding X-ray tomography data obtained at the Diamond Light Source, UK.
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Yao, A., C. L. Yang, J. K. Seo, and M. Soleimani. "EIT-Based Fabric Pressure Sensing." Computational and Mathematical Methods in Medicine 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/405325.
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This paper presents EIT-based fabric sensors that aim to provide a pressure mapping using the current carrying and voltage sensing electrodes attached to the boundary of the fabric patch. Pressure-induced shape change over the sensor area makes a change in the conductivity distribution which can be conveyed to the change of boundary current-voltage data. This boundary data is obtained through electrode measurements in EIT system. The corresponding inverse problem is to reconstruct the pressure and deformation map from the relationship between the applied current and the measured voltage on the fabric boundary. Taking advantage of EIT in providing dynamical images of conductivity changes due to pressure induced shape change, the pressure map can be estimated. In this paper, the EIT-based fabric sensor was presented for circular and rectangular sensor geometry. A stretch sensitive fabric was used in circular sensor with 16 electrodes and a pressure sensitive fabric was used in a rectangular sensor with 32 electrodes. A preliminary human test was carried out with the rectangular sensor for foot pressure mapping showing promising results.
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McClelland, Shearwood, Brian Kim, Linda M. Winfield, Blair Ford, Tresha A. Edwards, Seth L. Pullman, Qiping Yu, Guy M. McKhann, and Robert R. Goodman. "Microelectrode recording-determined subthalamic nucleus length not predictive of stimulation-induced side effects." Neurosurgical Focus 19, no. 5 (November 2005): 1–5. http://dx.doi.org/10.3171/foc.2005.19.5.14.
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Object Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects. Methods Eighty-two electrodes implanted in 75 patients between March 1999 and March 2003 were retrospectively examined to evaluate the length of the STN defined by MER, and the number of and threshold for postoperative stimulation-induced side effects. Electrodes were typically tested with increasing stimulation amplitudes (maximum 6 V) by using a monopolar array. The 82 electrodes were associated with 97 stimulation-induced side effects. The mean time between surgery and testing stimulation-induced side effects was 3.9 months. Statistical analysis (two-tailed t-test) revealed no significant difference in the number of stimulation-induced side effects (or the mean threshold for paresthesias, the most common side effect) for electrodes associated with an STN length less than 4.5 mm (13 electrodes) compared with those associated with an STN greater than or equal to 4.5 mm (69 electrodes, p = 0.616). For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). In the x axis (medial–lateral orientation), there was no systematic difference in adjustments made for the electrodes associated with the shorter compared with the longer STN lengths. In the y axis (anterior–posterior orientation), there was a very small statistically significant difference in the mean adjustment (0.4 mm) between the two groups. Conclusions Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.
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Munyon, Charles, Jennifer Sweet, Hans Luders, Samden Lhatoo, and Jonathan Miller. "The 3-Dimensional Grid." Operative Neurosurgery 11, no. 1 (January 16, 2015): 127–34. http://dx.doi.org/10.1227/neu.0000000000000649.
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Abstract BACKGROUND Successful surgical treatment of epilepsy requires accurate definition of areas of ictal onset and eloquent brain. Although invasive monitoring can help, subdural grids cannot sample sulci or subcortical tissue; traditional stereoelectroencephalography depth electrodes are usually placed too far apart to provide sufficient resolution for mapping. OBJECTIVE To report a strategy of depth electrode placement in a dense array to allow precise anatomic localization of epileptic and eloquent cortex. METHODS Twenty patients with medically intractable epilepsy either poorly localized or found to arise adjacent to eloquent areas underwent placement of arrays of depth electrodes into and around the putative area of seizure onset with the use of framed stereotaxy. Each array consisted of a “grid” of parallel electrodes in a rectangular pattern with 1 cm between entry sites. In a subset of patients, a few electrodes were placed initially, with additional electrodes placed in a second stage. Trajectories were modified to avoid cortical vessels defined on magnetic resonance imaging. Patients were monitored for 4 to 21 days to establish the precise location of seizure onset. Stimulation was performed to map cortical and subcortical eloquent regions. Electrode locations were coregistered for frameless stereotaxy during subsequent resection of seizure focus. RESULTS Two hundred fifty-four electrodes were implanted. Discrete regions of seizure onset and functional cortex were identified, which were used during resection to remove epileptogenic tissue while preserving eloquent areas. There were no hemorrhagic or infectious complications; no patient suffered permanent neurological deficit. CONCLUSION The 3-dimensional intraparenchymal grid is useful for identifying the location and extent of epileptic and eloquent brain.
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Casquero-Veiga, Marta, David García-García, Manuel Desco, and María Luisa Soto-Montenegro. "Understanding Deep Brain Stimulation: In Vivo Metabolic Consequences of the Electrode Insertional Effect." BioMed Research International 2018 (October 17, 2018): 1–6. http://dx.doi.org/10.1155/2018/8560232.
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Deep brain stimulation (DBS) is a neurosurgery technique widely used in movement disorders, although its mechanism of action remains unclear. In fact, apart from the stimulation itself, the mechanical insertion of the electrode may play a crucial role. Here we aimed to distinguish between the insertional and the DBS effects on brain glucose metabolism. To this end, electrodes were implanted targeting the medial prefrontal cortex in five adult male Wistar rats. Positron Emission Tomography (PET) studies were performed before surgery (D0) and seven (D7) and nine days (D9) after that. DBS was applied during the 18FDG uptake of the D9 study. PET data were analysed with statistical parametric mapping. We found an electrode insertional effect in cortical areas, while DBS resulted in a more widespread metabolic pattern. The consequences of simultaneous electrode and DBS factors revealed a combination of both effects. Therefore, the insertion metabolic effects differed from the stimulation ones, which should be considered when assessing DBS protocols.
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Otsubo, Hiroshi, Atsushi Shirasawa, Shiro Chitoku, James T. Rutka, Scott B. Wilson, and O. Carter Snead. "Computerized brain-surface voltage topographic mapping for localization of intracranial spikes from electrocorticography." Journal of Neurosurgery 94, no. 6 (June 2001): 1005–9. http://dx.doi.org/10.3171/jns.2001.94.6.1005.
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✓ The purpose of this paper is to describe the use of computerized brain-surface voltage topographic mapping to localize and identify epileptic discharges recorded on electrocorticographic (ECoG) studies in which a subdural grid was used during intracranial video electroencephalographic (IVEEG) monitoring. The authors studied 12 children who underwent surgery for intractable extrahippocampal epilepsy. Cortical surfaces and subdural grid electrodes were photographed during the initial surgery to create an electrode map that could be superimposed onto a picture of the brain surface. Spikes were selected from ictal discharges recorded at the beginning of clinically confirmed seizures and from interictal discharges seen on ECoG studies during IVEEG recording. A computer program was used to calculate the sequential amplitude of the spikes by using squared interpolation, and they were then superimposed onto the electrode map. Interictal discharges and high-amplitude spike complexes at seizure onset were plotted on the map. This mapping procedure depicted the ictal zone in nine patients and the interictal zone in 12, and proved to be an accurate and useful source of information for planning corrective surgery.
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Chiang, Chia-Han, Sang Min Won, Amy L. Orsborn, Ki Jun Yu, Michael Trumpis, Brinnae Bent, Charles Wang, et al. "Development of a neural interface for high-definition, long-term recording in rodents and nonhuman primates." Science Translational Medicine 12, no. 538 (April 8, 2020): eaay4682. http://dx.doi.org/10.1126/scitranslmed.aay4682.
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Long-lasting, high-resolution neural interfaces that are ultrathin and flexible are essential for precise brain mapping and high-performance neuroprosthetic systems. Scaling to sample thousands of sites across large brain regions requires integrating powered electronics to multiplex many electrodes to a few external wires. However, existing multiplexed electrode arrays rely on encapsulation strategies that have limited implant lifetimes. Here, we developed a flexible, multiplexed electrode array, called “Neural Matrix,” that provides stable in vivo neural recordings in rodents and nonhuman primates. Neural Matrix lasts over a year and samples a centimeter-scale brain region using over a thousand channels. The long-lasting encapsulation (projected to last at least 6 years), scalable device design, and iterative in vivo optimization described here are essential components to overcoming current hurdles facing next-generation neural technologies.
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Yang, Chen-Ya, Muh-Lii Liang, Hsin-Hung Chen, Jan-Wei Chiu, Kwong-Kum Liao, and Tsui-Fen Yang. "Using subdural strip electrodes to define functional sensory nerves and the most inferior functional portion of the conus medullaris during detethering surgeries for tethered cord syndrome: a pilot study." Journal of Neurosurgery: Spine 29, no. 4 (October 2018): 456–60. http://dx.doi.org/10.3171/2018.2.spine171240.
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OBJECTIVEThe aim of this study was to investigate the feasibility of using subdural strip electrodes, placed just rostral to the surgical field, to record sensory evoked potentials (SEPs) from the lumbosacral sensory nerves and define the most inferior functional portion of the conus medullaris during detethering surgery for spinal dysraphism and/or tethered cord syndrome (TCS).METHODSSix patients, 2 boys and 4 girls, aged 0.5 to 16 years, were enrolled in this study. One patient had lipomyelomeningocele-related, 4 had myelomeningocele-related, and 1 had diastematomyelia and lipomyelomeningocele-related TCS. In addition to the routine preparations that are needed for performing functional mapping and monitoring during surgery for spinal dysraphism and TCS, the patients had a 1 × 4 strip of electrodes placed rostral to the surgical field, where it was secured by a surgeon after opening the dura. With the patient under total intravenous anesthesia, the sensory nerves and conus medullaris were stimulated with a concentric bipolar electrode over the surgical field while SEPs were recorded with the strip electrodes to identify any possible sensory roots with remaining function and the most inferior functional portion of the conus medullaris.RESULTSThe SEP amplitudes that were recorded with the subdural strip electrodes ranged from 4 to 400 μV, and the responses to sensory nerve stimulation were frequently much larger than were those to conus stimulation. Use of the SEP recordings for sensory mapping along with the routine mapping and monitoring techniques allowed detethering to be completed such that none of the patients sustained any new functional deficit after surgery.CONCLUSIONSRecording SEPs from the functional sensory nerves and conus medullaris through subdural strip electrodes proved to be a feasible and valuable tool during detethering surgery in young patients. This approach may help surgeons achieve maximal detethering while preserving important sensory functions, consequently retaining the patient’s quality of life.
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Nitta, Takashi, Masaki Wakita, Yoshiyuki Watanabe, Hiroya Ohmori, Shun-ichiro Sakamoto, Yosuke Ishii, and Masami Ochi. "Double Potential Mapping: A Novel Technique for Locating the Site of Incomplete Ablation." Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 7, no. 6 (November 2012): 429–34. http://dx.doi.org/10.1177/155698451200700610.
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Objective Double potential mapping using bipolar electrodes that straddle the ablation line should identify the site of incomplete ablation as a conduction gap without constructing the activation maps. Methods Bipolar electrograms were recorded during pacing using 11 custom-made bipolar electrodes straddling the ablation line created by a bipolar radiofrequency ablation device on the lateral right atrium in seven canines. A linear ablation was made with an ablation device, of which one jaw was inserted into the atrium through a purse-string suture. A 3-mm-wide tape was placed on both jaws 10 mm from the tip of the ablation electrode to intentionally create an incomplete ablation lesion. The activation times at each dipole across the ablation line were defined as the times of the maximum positive and negative derivatives of the double potentials, and the site of conduction gap was determined as the site of the earliest activation across the linear ablation. The lateral right atrium was mapped simultaneously with 45 different bipolar electrodes to construct the activation maps and the earliest activation site across the ablation line was determined. Results The double potential mapping located the conduction gap on a real-time basis without displaying any maps. There was no significant change in the accuracy between the different times after ablation and different pacing cycle lengths. Conclusions Double potential mapping locates the conduction gap on a real-time basis and would be useful in beating-heart epicardial ablation in off-pump setting.
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Zhu, Pan, Wu, and Huan. "Optimized Electrode Locations for Wearable Single-Lead ECG Monitoring Devices: A Case Study Using WFEES Modules based on the LANS Method." Sensors 19, no. 20 (October 14, 2019): 4458. http://dx.doi.org/10.3390/s19204458.
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Body surface potential mapping (BSPM) is a valuable tool for research regarding electrocardiograms (ECG). However, the BSPM system is limited by its large number of electrodes and wires, long installation time, and high computational complexity. In this paper, we designed a wearable four-electrode electrocardiogram-sensor (WFEES) module that measures six-channel ECGs simultaneously for ECG investigation. To reduce the testing lead number and the measurement complexity, we further proposed a method, the layered (A, N) square-based (LANS) method, to optimize the ECG acquisition and analysis process using WFEES modules for different applications. Moreover, we presented a case study of electrode location optimization for wearable single-lead ECG monitoring devices using WFEES modules with the LANS method. In this study, 102 sets of single-lead ECG data from 19 healthy subjects were analyzed. The signal-to-noise ratio of ECG, as well as the mean and coefficient of variation of QRS amplitude, was derived among different channels to determine the optimal electrode locations. The results showed that a single-lead electrode pair should be placed on the left chest above the electrode location of standard precordial leads V1 to V4. Additionally, the best orientation was the principal diagonal as the direction of the heart’s electrical axis.
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Serletis, Demitre, Juan Bulacio, William Bingaman, Imad Najm, and Jorge González-Martínez. "The stereotactic approach for mapping epileptic networks: a prospective study of 200 patients." Journal of Neurosurgery 121, no. 5 (November 2014): 1239–46. http://dx.doi.org/10.3171/2014.7.jns132306.
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Object Stereoelectroencephalography (SEEG) is a methodology that permits accurate 3D in vivo electroclinical recordings of epileptiform activity. Among other general indications for invasive intracranial electroencephalography (EEG) monitoring, its advantages include access to deep cortical structures, its ability to localize the epileptogenic zone when subdural grids have failed to do so, and its utility in the context of possible multifocal seizure onsets with the need for bihemispheric explorations. In this context, the authors present a brief historical overview of the technique and report on their experience with 2 SEEG techniques (conventional Leksell frame-based stereotaxy and frameless stereotaxy under robotic guidance) for the purpose of invasively monitoring difficult-to-localize refractory focal epilepsy. Methods Over a period of 4 years, the authors prospectively identified 200 patients with refractory epilepsy who collectively underwent 2663 tailored SEEG electrode implantations for invasive intracranial EEG monitoring and extraoperative mapping. The first 122 patients underwent conventional Leksell frame-based SEEG electrode placement; the remaining 78 patients underwent frameless stereotaxy under robotic guidance, following acquisition of a stereotactic ROSA robotic device at the authors' institution. Electrodes were placed according to a preimplantation hypothesis of the presumed epileptogenic zone, based on a standardized preoperative workup including video-EEG monitoring, MRI, PET, ictal SPECT, and neuropsychological assessment. Demographic features, seizure semiology, number and location of implanted SEEG electrodes, and location of the epileptogenic zone were recorded and analyzed for all patients. For patients undergoing subsequent craniotomy for resection, the type of resection and procedure-related complications were prospectively recorded. These results were analyzed and correlated with pathological diagnosis and postoperative seizure outcomes. Results The epileptogenic zone was confirmed by SEEG in 154 patients (77%), of which 134 (87%) underwent subsequent craniotomy for epileptogenic zone resection. Within this cohort, 90 patients had a minimum follow-up of at least 12 months; therein, 61 patients (67.8%) remained seizure free, with an average follow-up period of 2.4 years. The most common pathological diagnosis was focal cortical dysplasia Type I (55 patients, 61.1%). Per electrode, the surgical complications included wound infection (0.08%), hemorrhagic complications (0.08%), and a transient neurological deficit (0.04%) in a total of 5 patients (2.5%). One patient (0.5%) ultimately died due to intracerebral hematoma directly ensuing from SEEG electrode placement. Conclusions Based on these results, SEEG methodology is safe, reliable, and effective. It is associated with minimal morbidity and mortality, and serves as a practical, minimally invasive approach to extraoperative localization of the epileptogenic zone in patients with refractory epilepsy.
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Noda, H., S. Murakami, J. Yamada, J. Tamada, Y. Tamaki, and T. Aso. "Saccadic eye movements evoked by microstimulation of the fastigial nucleus of macaque monkeys." Journal of Neurophysiology 60, no. 3 (September 1, 1988): 1036–52. http://dx.doi.org/10.1152/jn.1988.60.3.1036.
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1. Systematic exploration throughout the deep cerebellar nuclei and white matter disclosed that the region from which saccadic eye movements (saccades) were evoked with weak currents (less than 10 microA) was confined to the fastigial nucleus and the adjacent white matter. 2. When an electrode for stimulation was advanced in the cerebellum, saccades were evoked in the direction of the stimulated side (ipsilateral saccades) as it entered the low-threshold region. In some tracks, particularly when the electrode was advanced in the medial portion of the fastigial nucleus, the direction of the evoked saccades changed from the ipsilateral to the contralateral. 3. The mappings with microstimulation disclosed that the ipsilateral saccades were elicited from a relatively wide region that included almost the full extent of the fastigial nucleus. The low-threshold region continued in the white matter caudally into vermal lobule VII and rostrally into the dorsal aspect of the brachium conjunctivum. On the other hand, the contralateral saccades were evoked from a relatively circumscribed region in the ventromedial portion of the fastigial nucleus. 4. The reversal in the direction of the horizontal component occurred always in a narrow zone in the core of the fastigial nucleus. The caudal part of this zone coincided with an ellipsoidal region where anterogradely labeled axons of the Purkinje cells terminated when HRP was injected into vermal lobule VII. 5. When bicuculline (0.2-1 microgram) was injected in the ellipsoidal region, the ipsilateral saccades evoked from the dorsocaudal aspect of the region were suppressed for several hours. On the other hand, the contralateral saccades evoked from the ventromedial portion of the fastigial nucleus were either unchanged or enhanced. 6. Because the ipsilateral saccades were suppressed by bicuculline, they were most probably evoked by stimulation of the presynaptic component of gamma-amino-butyric acid-(GABA) mediated synapses, namely the axons of Purkinje cells. 7. Because stimulation of the presynaptic component of the inhibitory synapses evoked ipsilateral saccades, activation of the postsynaptic component would evoke contralateral saccades. In fact, the distribution of the fastigial sites yielding contralateral saccades coincided with the course of axons of fastigial neurons arising in the ellipsoidal region. It is most likely, therefore, that the contralateral saccades were evoked by stimulation of fastigial neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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Gonzalez-Martinez, Jorge, Jeffrey Mullin, Sumeet Vadera, Juan Bulacio, Gwyneth Hughes, Stephen Jones, Rei Enatsu, and Imad Najm. "Stereotactic placement of depth electrodes in medically intractable epilepsy." Journal of Neurosurgery 120, no. 3 (March 2014): 639–44. http://dx.doi.org/10.3171/2013.11.jns13635.
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Object Despite its long-reported successful record, with almost 60 years of clinical use, the technical complexity regarding the placement of stereoelectroencephalography (SEEG) depth electrodes may have contributed to the limited widespread application of the technique in centers outside Europe. The authors report on a simplified and novel SEEG surgical technique in the extraoperative mapping of refractory focal epilepsy. Methods The proposed technique was applied in patients with medically refractory focal epilepsy. Data regarding general demographic information, method of electrode implantation, time of implantation, number of implanted electrodes, seizure outcome after SEEG-guided resections, and complications were prospectively collected. Results From March 2009 to April 2012, 122 patients underwent SEEG depth electrode implantation at the Cleveland Clinic Epilepsy Center in which the authors' technique was used. There were 65 male and 57 female patients whose mean age was 33 years (range 5–68 years). The group included 21 pediatric patients (younger than 18 years). Planning and implantations were performed in a single stage. The time for planning was, on average, 33 minutes (range 20–47 minutes), and the time for implantation was, on average, 107 minutes (range 47–150 minutes). Complications related to the SEEG technique were observed in 3 patients. The calculated risk of complications per electrode was 0.18%. The seizure-free rate after SEEG-guided resections was 62% in a mean follow-up period of 12 months. Conclusions The authors report on a safe, simplified, and less time-consuming method of SEEG depth electrode implantation, using standard and widely available surgical tools, making the technique a reasonable option for extraoperative monitoring of patients with medically intractable epilepsy in centers lacking the Talairach stereotactic armamentarium.
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Black, Bryan J., Aswini Kanneganti, Alexandra Joshi-Imre, Rashed Rihani, Bitan Chakraborty, Justin Abbott, Joseph J. Pancrazio, and Stuart F. Cogan. "Chronic recording and electrochemical performance of Utah microelectrode arrays implanted in rat motor cortex." Journal of Neurophysiology 120, no. 4 (October 1, 2018): 2083–90. http://dx.doi.org/10.1152/jn.00181.2018.
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Multisite implantable electrode arrays serve as a tool to understand cortical network connectivity and plasticity. Furthermore, they enable electrical stimulation to drive plasticity, study motor/sensory mapping, or provide network input for controlling brain-computer interfaces. Neurobehavioral rodent models are prevalent in studies of motor cortex injury and recovery as well as restoration of auditory/visual cues due to their relatively low cost and ease of training. Therefore, it is important to understand the chronic performance of relevant electrode arrays in rodent models. In this report, we evaluate the chronic recording and electrochemical performance of 16-channel Utah electrode arrays, the current state-of-the-art in pre-/clinical cortical recording and stimulation, in rat motor cortex over a period of 6 mo. The single-unit active electrode yield decreased from 52.8 ± 10.0 ( week 1) to 13.4 ± 5.1% ( week 24). Similarly, the total number of single units recorded on all electrodes across all arrays decreased from 106 to 15 over the same time period. Parallel measurements of electrochemical impedance spectra and cathodic charge storage capacity exhibited significant changes in electrochemical characteristics consistent with development of electrolyte leakage pathways over time. Additionally, measurements of maximum cathodal potential excursion indicated that only a relatively small fraction of electrodes (10–35% at 1 and 24 wk postimplantation) were capable of delivering relevant currents (20 µA at 4 nC/ph) without exceeding negative or positive electrochemical potential limits. In total, our findings suggest mainly abiotic failure modes, including mechanical wire breakage as well as degradation of conducting and insulating substrates. NEW & NOTEWORTHY Multisite implantable electrode arrays serve as a tool to record cortical network activity and enable electrical stimulation to drive plasticity or provide network feedback. The use of rodent models in these fields is prevalent. We evaluated chronic recording and electrochemical performance of 16-channel Utah electrode arrays in rat motor cortex over a period of 6 mo. We primarily observed abiotic failure modes suggestive of mechanical wire breakage and/or degradation of insulation.
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Telecki, Igor, Sanja Grujovic-Zdolsek, Petar Belicev, Srdjan Petrovic, and Nebojsa Neskovic. "Spatial rainbows and catastrophes in transmission of protons through electrostatic hexapole lens." Nuclear Technology and Radiation Protection 33, no. 3 (2018): 231–38. http://dx.doi.org/10.2298/ntrp1803231t.
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This work reports on the spatial rainbows occurring in transmission of 10 keV protons through hexapole lens. Positive potentials of the lens electrodes are set to be 0.9, 2, and 5 kV. The spatial rainbows and corresponding proton distributions are calculated by using an accurate analytical approximation of the numerically obtained lens potential. Further, for the positive potential of the lens electrode equal to 0.9 kV, it has been shown that application of catastrophe theory leads to a simple polynomial non-linear mapping, generating accurate spatial rainbows at the exit and in the drift space behind the lens.
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Starr, Philip A., Robert S. Turner, Geoff Rau, Nadja Lindsey, Susan Heath, Monica Volz, Jill L. Ostrem, and William J. Marks. "Microelectrode-guided implantation of deep brain stimulators into the globus pallidus internus for dystonia: techniques, electrode locations, and outcomes." Journal of Neurosurgery 104, no. 4 (April 2006): 488–501. http://dx.doi.org/10.3171/jns.2006.104.4.488.
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Object Deep brain stimulation (DBS) of the globus pallidus internus (GPI) is a promising new procedure for the treatment of dystonia. The authors describe their technical approach for placing electrodes into the GPI in awake patients with dystonia, including methodology for electrophysiological mapping of the GPI in the dystonic state, clinical outcomes and complications, and the location of electrodes associated with optimal benefit. Methods Twenty-three adult and pediatric patients with various forms of dystonia were included in this study. Baseline neurological status and DBS-related improvement in motor function were measured using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). The implantation of DBS leads was performed using magnetic resonance (MR) imaging–based stereotaxy, single-cell microelectrode recording, and intraoperative test stimulation to determine thresholds for stimulation-induced adverse effects. Electrode locations were measured on computationally reformatted postoperative MR images according to a prospective protocol. Conclusions Physiologically guided implantation of DBS electrodes in patients with dystonia was technically feasible in the awake state in most patients, and the morbidity rate was low. Spontaneous discharge rates of GPI neurons in dystonia were similar to those of globus pallidus externus neurons, such that the two nuclei must be distinguished by neuronal discharge patterns rather than rates. Active electrode locations associated with robust improvement (> 70% decrease in BFMDRS score) were located near the intercommissural plane, at a mean distance from the pallidocapsular border of 3.6 mm.
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Escabí, Monty A., Heather L. Read, Jonathan Viventi, Dae-Hyeong Kim, Nathan C. Higgins, Douglas A. Storace, Andrew S. K. Liu, et al. "A high-density, high-channel count, multiplexed μECoG array for auditory-cortex recordings." Journal of Neurophysiology 112, no. 6 (September 15, 2014): 1566–83. http://dx.doi.org/10.1152/jn.00179.2013.
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Our understanding of the large-scale population dynamics of neural activity is limited, in part, by our inability to record simultaneously from large regions of the cortex. Here, we validated the use of a large-scale active microelectrode array that simultaneously records 196 multiplexed micro-electrocortigraphical (μECoG) signals from the cortical surface at a very high density (1,600 electrodes/cm2). We compared μECoG measurements in auditory cortex using a custom “active” electrode array to those recorded using a conventional “passive” μECoG array. Both of these array responses were also compared with data recorded via intrinsic optical imaging, which is a standard methodology for recording sound-evoked cortical activity. Custom active μECoG arrays generated more veridical representations of the tonotopic organization of the auditory cortex than current commercially available passive μECoG arrays. Furthermore, the cortical representation could be measured efficiently with the active arrays, requiring as little as 13.5 s of neural data acquisition. Next, we generated spectrotemporal receptive fields from the recorded neural activity on the active μECoG array and identified functional organizational principles comparable to those observed using intrinsic metabolic imaging and single-neuron recordings. This new electrode array technology has the potential for large-scale, temporally precise monitoring and mapping of the cortex, without the use of invasive penetrating electrodes.
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Fediuk, Annika, Dennis Wilken, Martin Thorwart, Tina Wunderlich, Ercan Erkul, and Wolfgang Rabbel. "The Applicability of an Inverse Schlumberger Array for Near-Surface Targets in Shallow Water Environments." Remote Sensing 12, no. 13 (July 3, 2020): 2132. http://dx.doi.org/10.3390/rs12132132.
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We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude that offshore geoelectric sounding allows the mapping of archaeological stone settings. The material differentiation of low-porosity rock masses < 15% is critical. Submerged wooden objects show a significant resistivity contrast to sand and rocks. Distinguishing brine-saturated sandy sediments from cohesive silty-clayey sediments is difficult due to their equal or reversed resistivity contrasts. Submarine freshwater discharges in sandy aquifers can be localized well, though difficulties may occur if the seafloor encounters massive low-porosity rock masses. As to the measurement setups, submerged and floating electrodes differ in their spatial resolution. Whereas stone settings of 0.5 to 1 m can still be located with submerged electrodes within the uppermost 4 m underneath the seafloor, they have to be >2 m if floating electrodes are used. Therefore, we recommend using submerged electrodes, especially in archaeological prospection. Littoral geological and hydrogeological mapping is also feasible with floating electrodes in a more time-saving way.
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Barolat, Giancarlo, Fulvio Massaro, Jiping He, Sergio Zeme, and Beth Ketcik. "Mapping of sensory responses to epidural stimulation of the intraspinal neural structures in man." Journal of Neurosurgery 78, no. 2 (February 1993): 233–39. http://dx.doi.org/10.3171/jns.1993.78.2.0233.
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✓ A database is presented of sensory responses to electrical stimulation of the dorsal neural structures at various spine levels in 106 subjects subjected to epidural spinal cord stimulation. All patients were implanted for chronic pain management and were able to perceive stimulation in the area of pain. All patients entered in this study were able to reliably report their stimulation pattern. Several patients were implanted with more than one electrode array. The electrode arrays were placed in the dorsal epidural space at levels between C-1 and L-1. The structures that were likely involved include the dorsal roots, dorsal root entry zone, dorsal horn, and dorsal columns. At the present time, exact characterization of the structure being stimulated is possible only in limited instances. Various body areas are presented with the correspondent spine levels where implanted electrodes generate paresthesias. Areas that are relatively easy targets for stimulation are the median aspect of the hand, the abdominal wall, the anterior aspect of the thigh, and the foot. Some areas are particularly difficult to cover with stimulation-induced paresthesias; these include the C-2 distribution, the neck, the low back, and the perineum.
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Kätelhön, Enno, Dirk Mayer, Marko Banzet, Andreas Offenhäusser, and Bernhard Wolfrum. "Nanocavity crossbar arrays for parallel electrochemical sensing on a chip." Beilstein Journal of Nanotechnology 5 (July 23, 2014): 1137–43. http://dx.doi.org/10.3762/bjnano.5.124.
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We introduce a novel device for the mapping of redox-active compounds at high spatial resolution based on a crossbar electrode architecture. The sensor array is formed by two sets of 16 parallel band electrodes that are arranged perpendicular to each other on the wafer surface. At each intersection, the crossing bars are separated by a ca. 65 nm high nanocavity, which is stabilized by the surrounding passivation layer. During operation, perpendicular bar electrodes are biased to potentials above and below the redox potential of species under investigation, thus, enabling repeated subsequent reactions at the two electrodes. By this means, a redox cycling current is formed across the gap that can be measured externally. As the nanocavity devices feature a very high current amplification in redox cycling mode, individual sensing spots can be addressed in parallel, enabling high-throughput electrochemical imaging. This paper introduces the design of the device, discusses the fabrication process and demonstrates its capabilities in sequential and parallel data acquisition mode by using a hexacyanoferrate probe.
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Darcey, Terrance M., and David W. Roberts. "Technique for the localization of intracranially implanted electrodes." Journal of Neurosurgery 113, no. 6 (December 2010): 1182–85. http://dx.doi.org/10.3171/2009.12.jns091678.
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Object The anatomical localization of electrodes in the human brain is important for the interpretation of pathophysiological (epileptifom spikes, seizures) and functional data (stimulation mapping, evoked potentials). Electroencephalography and evoked potentials are volume-conducted field effects that are most easily interpreted with knowledge of the location and topology of adjacent structures, and brain stimulation techniques produce current fields whose effects are highly dependent on the geometry of electrode assemblies in relation to adjacent structures. In this paper, the authors describe a straightforward method for implanted electrode localization, and detail their experience to date with the technique. Methods The described method is based on the coregistration of preoperative MR imaging studies with postimplant CT scans by using standard mutual information optimization of rigid body transformation of the CT to the MR image. Fused images of the MR and thresholded CT images are derived, and electrodes are visualized using various standard computer projections, renderings, and measurement tools. Results The authors have successfully used the described method over an extended period to localize electrode contacts in intracranial implants for seizure localization, and in long-term implants for movement disorders and seizure control. The accuracy of localization is very good, although it is dependent on image quality and possible brain shift between acquisition of the CT and MR images. Conclusions This method is easily implemented and is useful for a wide variety of clinical and research applications. It is a straightforward process to extend it to additional image modalities that are emerging for surgical planning and image guidance.
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Sweet, Jennifer A., Benjamin L. Walter, Charles Munyon, and Jonathan P. Miller. "Multitract Orthogonal Microelectrode Localization of the Subthalamic Nucleus: Description of a Novel Technique." Operative Neurosurgery 10, no. 2 (January 19, 2014): 240–45. http://dx.doi.org/10.1227/neu.0000000000000295.
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Abstract BACKGROUND: Microelectrode recording helps surgeons accurately localize boundaries of the subthalamic nucleus (STN) and surrounding structures in deep brain stimulation. OBJECTIVE: To describe a novel adaptation of the Ben gun device to optimize efficient mapping. METHODS: Patients who underwent STN deep brain stimulation over a 3-year period were reviewed. For the final year, the Ben gun was rotated 45° and the target was offset 1.4 mm lateral and anterior in the plane orthogonal to the intended trajectory to allow for simultaneous parallel tracks at target, 2.8 mm anterior (localizing the front of STN), and 2.8 mm lateral (identifying the internal capsule). Before this step, the initial pass consisted of 1 to 2 tracks with the frame center targeted to STN. The primary outcome measure was the number of passes required for accurate localization of the nucleus and boundaries. RESULTS: Eighty-three electrodes were implanted in 45 patients (mean age, 62; range, 37-78 years), of which 29 electrodes were placed by the use of the new technique. One electrode (4%) required more than 1 pass using the new technique compared with 36 (67%) using the older technique (P < .01). The distance from original target to final electrode position increased from 0.67 ± 0.13 mm to 1.06 ± 0.15 mm (P < .05) with a greater tendency to move the final electrode position posteriorly. There was no statistically significant difference in benefit from neurostimulation. CONCLUSION: This technique facilitates reliable localization of the STN with fewer passes, possibly decreasing the risks associated with more passes and longer duration of surgery.
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Watanabe, Hidehiko, Jean-Benoît Perry, Pierre Pagé, Pierre Savard, and Réginald Nadeau. "Vagal effects on sinoatrial and atrial conduction studied with epicardial mapping in dogs: the influence of pacemaker shifts on the measurement of sinoatrial conduction time." Canadian Journal of Physiology and Pharmacology 63, no. 2 (February 1, 1985): 113–21. http://dx.doi.org/10.1139/y85-021.
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The influence of pacemaker shifts on sinoatrial conduction time (SACT) was studied by investigating the effects of vagal stimulation on SACT and atrial conduction in anesthetized open-chest dogs. Isochronal maps were drawn from unipolar electrograms simultaneously recorded at 60 epicardial sites on the right atrial free wall and the inferior and superior vena cava. Vagal stimulation caused atrial conduction velocity to increase from 0.99 ± 0.10 m/s (mean ± SD) to 1.23 ± 0.23 m/s (p < 0.01), and the pacemaker to shift to lower positions along the superior vena cava – right atrial junction. As a result of the changes, the distances and the atrial conduction times from the stimulating and recording electrodes to the pacemaker site varied, and hence, the SACT values obtained indirectly by premature atrial stimulation varied. The isochronal maps were used to measure the atrial conduction times from stimulating to recording electrodes (a), from stimulating electrode to pacemaker site (b), and from pacemaker site to recording electrode (c). Indirect SACT was lengthened by vagal stimulation from 43 ± 16 to 64 ± 22 ms (p < 0.02). After correcting by subtracting the atrial conduction time (b + c − a), these values became 26 ± 6 ms (control) and 40 ± 11 ms (vagal stimulation) (p < 0.01). SACT values measured directly from the electrograms were 27 ± 7 ms (control) and 42 ± 10 ms (vagal stimulation) (p < 0.01). Corrected indirect SACTs were closer to direct SACTs than were the uncorrected indirect SACTs. It was concluded that (i) vagal stimulation induced pacemaker shift, increased atrial conduction velocity, and prolonged SACT; (ii) constant atrial pacing induced a pacemaker shift toward the stimulating electrode; and (iii) atrial conduction time must be taken into account to correctly estimate SACT.