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We performed optical intrinsic signal imaging of cat primary visual cortex (Area 17 and 18) while delivering bipolar electrical stimulation to the retina by way of a supra-choroidal electrode array. Using a general linear model (GLM) analysis we identified statistically significant (p <;; 0.01) activation in a localized region of cortex following supra-threshold electrical stimulation at a single...
A miniaturized, hermetically-encased, wirelessly-operated retinal prosthesis has been developed for pre-clinical studies in Yucatan minipig animal models. The prosthesis attaches conformally to the outside of the eye and drives a microfabricated thin-film polyimide stimulating electrode array with sputtered iridium oxide electrodes. This array is implanted in the subretinal space using a specially-designed...
Electrical stimulation of the remaining retinal neurons to restore useful vision has been recently proposed in patients with retinitis pigmentosa(RP) or age-related macular degeneration(AMD). A critical element of a retinal prosthesis is the stimulating electrode array, which is placed in close proximity to the retina. It is via the retinal-electrode interface that a retinal prosthesis electrically...
Electro-tactile based rehabilitation systems must be capable of self-tuning to suit the tactile preference of different users. However, tactile preference is difficult to assess in practice. We propose a Takagi-Sugeno-Kang (TSK) fuzzy logic modeling and control approach for the on-line assessment of tactile preference. The method relies on real-time measurements of voltage and power absorbed by the...
The purpose of this study is to support communication of individuals with motor paralysis having difficulty verbally communicating due to illnesses such as Guillain-Barre Syndrome or brain-stem infarction. We have developed and describe a pointing device controlled by DC-coupled electrooculograms (EOGs). The visual angle of the subject is estimated from the amplitude of vertical and horizontal EOGs...
Computational and experimental bioelectromagnetics play an important role in the development of an epi-retinal prosthesis to restore partial vision to the blind. Specifically, the design of telemetry systems for power and data transfer, SAR analysis to ensure safety, and improvement of the effectiveness of the neursotimulator in general are areas of great interest. We will present an overview of the...
Thalamic visual neuroprostheses to be implanted in the lateral geniculate nucleus of the thalamus (the intermediate relay station of visual information from the retina to the cortex) could be used to provide visual information to blind people when retinal implants are not feasible. The main objective of the present work was to (i) determine a way to compare visual percepts generated by electrical...
A prototype neuro-stimulus chip for sub-retinal implants in blind patients affected by age-related macular degeneration (AMD) or retinitis pigmentosa (RP) is presented in this paper. This retinal prosthetic chip was designed to replace the degenerated photoreceptor cells, and in order to stimulate directly the remaining healthy layers of retinal neurons. The current stimulus circuits are monolithic...
The retinal prosthesis is aimed to restore partial vision to the blind affected by outer retinal degenerative diseases. Almost all research efforts rely on a dual-unit system, with components internal and external to the human body, including a video camera, an inductive wireless link for power and/or data transfer between the external and internal components, a processing microchip, and a stimulating...
A finite element model of epiretinal stimulation is presented, consisting of a continuum description of active retinal tissue in contact with bulk vitreous fluid. Simulations were undertaken to investigate the effect of mesh element size in the finite element model on threshold current. The threshold current varied by approximately 0.6% when the maximum mesh element size was changed from 125 to 225...
We are developing prosthetics for patients suffering from peripheral vestibular dysfunction. We tested a sensory-replacement prosthesis that stimulates neurons innervating the vestibular system by providing chronic pulsatile stimulation to electrodes placed in monkeys' lateral semicircular canals, which were plugged bilaterally, and used head angular velocity to modulate the current pulse rate. As...
A prototype of an epi-retinal vision prosthesis based upon an efficient electrode addressing schema has been developed. This system has the ability to stimulate multiple electrode regions simultaneously, hence greatly improving the maximum rate of stimulation compared to many currently available neural stimulation devices based on serial stimulation protocols. To minimize the problem of cross talk...
Recent clinical trials using modified cochlear implants employ a small number of electrodes to stimulate surviving retinal neurons in blind patients and indicate that spatially-mapped phosphenes may indeed be elicited through these means. The next obvious step forward in the path toward achieving a useful visual prosthesis for the blind will be to increase the quantity of stimulation sites such that...
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