Mimicking neural coding in retinal ganglion cells with short pulse electrical stimulation
A method, device and system for stimulating visual tissue, typically in the retina or visual cortex, to achieve an artificial percept of light or image. The method includes providing stimulating electrodes suitable for placement in proximity to the visual tissue and generating a series of short-duration stimulation signals having a duration of less than about 0.5 milliseconds each. The short-duration stimulation signals are applied through the stimulating electrodes with varying frequencies that are substantially matched to a spiking range of frequencies of at least one ganglion cell for perceiving brightness or image.
1. A method of stimulating a localized portion of visual tissue comprising the steps of:
providing a two dimensional array of stimulating electrodes suitable for placement in proximity to the visual tissue;
generating a plurality of stimulation signals adapted to mimic neural coding by eliciting a single spike response in at least one visual neuron per stimulation pulse, wherein said generating comprises selecting an amplitude and selecting a frequency of greater than or equal to 1 Hertz and less than or equal to 250 Hertz; and
applying said plurality of stimulation signals to said two dimensional array of stimulating electrodes, thereby stimulating the localized portion of the visual tissue and creating perception of light in formed images.
2. The method of claim 1 , wherein said plurality of stimulation signals comprise biphasic signals having a negative portion and a positive portion.
3. The method of claim 2 , wherein the localized portion of the visual tissue comprises at least one visual neuron.
4. The method of claim 3 wherein the at least one visual neuron is at least one retinal neuron.
5. The method of claim 4 , wherein the at least one retinal neuron is at least one ganglion cell.
6. The method of claim 3 , wherein said stimulating the localized portion comprises: stimulating at least one ganglion cell to the substantial exclusion of direct stimulation of the deeper retinal cells.
7. The method of claim 6 , further comprising; stimulating the at least one ganglion cell with stimulation signals having varying frequencies corresponding to varying levels of brightness.
8. The method of claim 1 , wherein said generating further comprises selecting a duration of less than about 1 millisecond for each of the stimulation signals.