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Greenville, TX, United States

Ghanbari Y.,Southern Methodist University | Papamichalis P.E.,Southern Methodist University | Spence L.,Plexon Inc.
IEEE Transactions on Biomedical Engineering

Analysis of extracellular recordings of neural action potentials (known as spikes) is highly dependent upon the accuracy of neural waveform classification, commonly referred to as spike sorting. Feature extraction is an important stage of this process because it can limit the quality of clustering that is performed in the feature space. Principal components analysis (PCA) is the most commonly used feature extraction method employed for neural spike recordings. To improve upon PCAs feature extraction performance for neural spike sorting, we revisit the PCA procedure to analyze its weaknesses and describe an improved feature extraction method. This paper proposes a linear feature extraction technique that we call graph-Laplacian features, which simultaneously minimizes the graph Laplacian and maximizes variance. The algorithms performance is compared with PCA and a wavelet-coefficient-based feature extraction algorithm on simulated single-electrode neural data. A cluster-quality metric is proposed to quantitatively measure the algorithm performance. The results show that the proposed algorithm produces more compact and well-separated clusters compared to the other approaches. © 2006 IEEE. Source

Clements I.P.,Georgia Institute of Technology | Clements I.P.,Plexon Inc. | Mukhatyar V.J.,Georgia Institute of Technology | Srinivasan A.,Georgia Institute of Technology | And 4 more authors.
IEEE Transactions on Neural Systems and Rehabilitation Engineering

Advances in neural interfacing technology are required to enable natural, thought-driven control of a prosthetic limb. Here, we describe a regenerative electrode design in which a polymer-based thin-film electrode array is integrated within a thin-film sheet of aligned nanofibers, such that axons regenerating from a transected peripheral nerve are topographically guided across the electrode recording sites. Cultures of dorsal root ganglia were used to explore design parameters leading to cellular migration and neurite extension across the nanofiber/electrode array boundary. Regenerative scaffold electrodes (RSEs) were subsequently fabricated and implanted across rat tibial nerve gaps to evaluate device recording capabilities and influence on nerve regeneration. In 20 of these animals, regeneration was compared between a conventional nerve gap model and an amputation model. Characteristic shaping of regenerated nerve morphology around the embedded electrode array was observed in both groups, and regenerated axon profile counts were similar at the eight week end point. Implanted RSEs recorded evoked neural activity in all of these cases, and also in separate implantations lasting up to five months. These results demonstrate that nanofiber-based topographic cues within a regenerative electrode can influence nerve regeneration, to the potential benefit of a peripheral nerve interface suitable for limb amputees. © 2001-2011 IEEE. Source

Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 102.13K | Year: 2008

DESCRIPTION (provided by applicant): Plexon Inc will coat the active sites of metal microelectrodes with carbon nanotubes and carbon nanotube/conductive polymer composite materials. We will measure effects of these coatings on electrode capacitance and imp edance, and examine the coating morphology and composition using scanning electron microscopy and energy-dispersive X-ray analysis. We present data that demonstrates that carbon nanotube coated electrodes dramatically increase the ability to electrically s timulate and record from neural tissue. This grant will allow perfecting the ability to precisely coat commercially available microelectrodes with nanoscale materials and quantify the electrochemical performance increases imparted by the coatings. The abil ity to reliably and reproducibly apply nanotube coatings to microelectrodes means Plexon can expand its current business model to include a consumables product line. The electrodes we will coat are already widely used in the research and clinical communiti es, permitting customers to improve their recording and stimulating capabilities without requiring the purchase of expensive equipment or modifying their techniques. PUBLIC HEALTH RELEVANCE Electrical stimulation of nerve cells through implanted electrode s is widely employed in neural prostheses for supplementing impaired hearing and vision, and has become central to a number of clinical therapies to treat conditions such as Parkinson's disease, dystonia, and chronic pain. The performance of current electr odes degrades over time; thus the neural prostheses using them have limited lifetimes. We have shown that modifying active sites of the electrodes with carbon nanotubes yields dramatic improvements in the ability to communicate with nerve cells, potentiall y yielding large increases in the useful life of neural prosthetic devices, with concomitant improvements in the quality of life for the prosthetic patient.

Ware T.,University of Texas at Dallas | Simon D.,University of Texas at Dallas | Arreaga-Salas D.E.,University of Texas at Dallas | Reeder J.,University of Texas at Dallas | And 3 more authors.
Advanced Functional Materials

A novel processing method is described using photolithography to pattern thin-film flexible electronics on shape memory polymer substrates with mechanical properties tailored to improve biocompatability and enhance adhesion between the polymer substrate and metal layers. Standard semiconductor wafer processing techniques are adapted to enable robust device design onto a variety of softening substrates with tunable moduli. The resulting devices are stiff enough (shear modulus of ≈700 MPa) to assist with device implantation and then soften in vivo (≈300 kPa) approaching the modulus of brain tissue (≈10 kPa) within 24 h. Acute in vivo studies demonstrate that these materials are capable of recording neural activity. Softening multi-electrode arrays offer a highly customizable interface, which can be optimized to improve biocompatibility, enabling the development of robust, reliable neural electrodes for neural engineering and neuroscience. 8-channel cortical probes are fabricated using the transfer-by-polymerization process with substrates that soften under physiological conditions. Single unit action potential recordings are shown from rat somatosensory cortex with a shape memory polymer (SMP)-gold electrode array during an acute experiment. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Plexon Inc. | Date: 2014-10-20

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