Journal of neuroscience methods
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J. Neurosci. Methods · Jun 2009
Plausibility assessment of a 2-state self-paced mental task-based BCI using the no-control performance analysis.
The feasibility of having a self-paced brain-computer interface (BCI) based on mental tasks is investigated. The EEG signals of four subjects performing five mental tasks each are used in the design of a 2-state self-paced BCI. The output of the BCI should only be activated when the subject performs a specific mental task and should remain inactive otherwise. ⋯ The classifier with a zero false positive rate and the highest true positive rate is selected as the best classifier. The classifiers tested include: linear discriminant analysis, quadratic discriminant analysis, Mahalanobis discriminant analysis, support vector machine, and radial basis function neural network. The results show that: (1) some classifiers obtained the desired zero false positive rate; (2) the linear discriminant analysis classifier does not yield acceptable performance; (3) the quadratic discriminant analysis classifier outperforms the Mahalanobis discriminant analysis classifier and performs almost as well as the radial basis function neural network; and (4) the support vector machine classifier has the highest true positive rates but unfortunately has nonzero false positive rates in most cases.
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J. Neurosci. Methods · Jun 2009
Culturing thick brain slices: an interstitial 3D microperfusion system for enhanced viability.
Brain slice preparations are well-established models for a wide spectrum of in vitro investigations in the neuroscience discipline. However, these investigations are limited to acute preparations or thin organotypic culture preparations due to the lack of a successful method that allows culturing of thick organotypic brain slices. Thick brain slice cultures suffer necrosis due to ischemia deep in the tissue resulting from a destroyed circulatory system and subsequent diffusion-limited supply of nutrients and oxygen. ⋯ Our perfusion method allows up to 84.6% viability (p<0.01) and up to 700 microm thickness, even after 5 DIV. Our results also confirm that these cultures are functionally active and have their in vivo cyto-architecture preserved. Prolonged viability of thick organotypic brain slice cultures will benefit scientists investigating network properties of intact organotypic neuronal networks in a reliable and repeatable manner.
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J. Neurosci. Methods · Jun 2009
A cortical (V1) neurophysiological recording model for assessing the efficacy of retinal visual prostheses.
A significant barrier to the development of a retinal prosthesis that is capable of inducing spatially patterned visual percepts has been a lack of adequate models to assess the efficacy of various electrical stimulation algorithms. Toward this end, we developed an in vivo, normally sighted animal model that is based on primary visual cortex neurophysiological recordings of spiking and local-field potential activity. ⋯ Furthermore, our model indicates that the short latency response originates in widespread retinal locations that extend well beyond the location of the activated electrodes, whereas the long latency response has a more focal origin which corresponds to the location of the activated electrodes. The present work demonstrates the applicability of our model for the evaluation and development of electrical retinal stimulation methods using cortical recordings.
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J. Neurosci. Methods · May 2009
Spinal reflex in human lower leg muscles evoked by transcutaneous spinal cord stimulation.
The H-reflex is one of the most common and useful techniques in the field of motor control. However, the H-reflex technique also involves difficulty in data interpretation when stimulus intensity is high enough to stimulate both sensory and motor fibers (antidromic current). On the other hand, transcutaneous stimulation applied on the spinous processes is able to stimulate the dorsal root, resulting in selective stimulation of only sensory fibers without evoking a direct motor response and antidromic current on the motor fibers. ⋯ Although not significant, H(max) amplitude in SOL by SS (76%) was also greater than that by PS (60%). It is suggested that transcutaneous stimulation is able to evoke H-reflex without a direct motor response. H(max) amplitudes traditionally measured by stimulation applied to a mixed nerve may underestimate the potential connectivity between the sensory and motor systems in humans.
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The reactive tissue response of the brain to chronically implanted materials remains a formidable obstacle to stable recording from implanted microelectrodes. One approach to mitigate this response is to apply a bioactive coating in the form of an ultra-porous silica sol-gel, which can be engineered to improve biocompatibility and to enable local drug delivery. The first step in establishing the feasibility of such a coating is to investigate the effects of the coating on electrode properties. ⋯ The voltammograms revealed a slight increase in charge carrying capacity of the electrodes following coating. Impedance spectrograms showed a mild increase in impedance at high frequencies but a more pronounced decrease in impedance at mid to low frequencies. These results demonstrate the feasibility of applying silica sol-gel coatings to silicon-based microelectrodes and are encouraging for the continued investigation of their use in mitigating the reactive tissue response.