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PURPOSE To investigate the spatiotemporal properties of the cortical responses elicited by intraorbital optic nerve (ON) stimulation with penetrating electrodes as means of designing optimal stimulation strategies for an ON visual prosthesis. METHODS The ON of rabbits was exposed by orbital surgery for electrical stimulation. Craniotomy was performed to(More)
In visual prosthesis research, electrically evoked potentials (EEPs) can be elicited by one or more biphasic current pulses delivered to the optic nerve (ON) through penetrating electrodes. Multi-channel EEPs recorded from the visual cortex usually contain large stimulus artifacts caused by instantaneous electrotonic current spread through the brain tissue.(More)
PURPOSE To investigate the response properties of the electrically evoked potentials (EEPs) elicited by intraorbital optic nerve stimulation with penetrating electrodes using different stimulus parameters. METHODS Visually evoked potentials (VEPs) were recorded as a control and for comparative purposes. Teflon-coated tungsten wire electrodes (100 microm(More)
PURPOSE The use of phosphenes evoked by transcorneal electrical stimulation (TcES) has been proposed as a means of residual visual function evaluation and candidate selection before implantation of retinal prostheses. Compared to the subjective measures, measurement of neuronal activity in visual cortex can objectively and quantitatively explore their(More)
Understanding the mechanisms underlying negative hemodynamic responses is critical for the interpretation of functional brain imaging signals. Negative imaging signals have been found in the visual, somatosensory and motor cortices in functional magnetic resonance imaging (fMRI) and intrinsic signal optical imaging (ISOI) studies. However, the origin of(More)
Purpose Current steering is a neural stimulation strategy that uses simultaneous stimulation of adjacent electrodes to produce additional intermediate stimulation sites and thus improves spatial resolution. We investigated the feasibility of current steering using electrophysiological and computational methods after implanting paired penetrating electrodes(More)
Negative hemodynamic response has been widely reported in blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging studies, however its origin is still controversial. Optical intrinsic signal (OIS) imaging can be used to study brain activity by simultaneously recording hemodynamic signals at different wavelengths with high spatial(More)
BACKGROUND Suprachoroidal-transretinal stimulation (STS) can potentially restore vision. This study investigated the spatial characteristics of cortical electrical evoked potentials (EEPs) elicited by STS. METHODS A 4 × 4 thin-film platinum microelectrode stimulating array (200 μm electrode diameter and 400 μm center-to-center distance) was fabricated by(More)
PURPOSE To investigate the effect of different stimulation modes on cortical electrically evoked potentials (EEPs) by intraorbital optic nerve (ON) stimulation with penetrating electrodes. METHODS A stimulating electrode array with three electrodes arranged linearly was inserted into the ON along its axis. EEPs were recorded using a 4 × 4 silver-ball(More)