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Recent advent of optogenetics has enabled activation of genetically-targeted neuronal cells using low intensity blue light
with high temporal precision. Since blue light is attenuated rapidly due to scattering and absorption in neural tissue,
optogenetic treatment of neurological disorders may require stimulation of specific cell types in multiple regions of the
brain. Further, restoration of certain neural functions (vision, and auditory etc) requires accurate spatio-temporal
stimulation patterns rather than just precise temporal stimulation. In order to activate multiple regions of the central
nervous system in 3D, here, we report development of an optogenetic prosthetic comprising of array of fibers coupled to
independently-controllable LEDs. This design avoids direct contact of LEDs with the brain tissue and thus does not
require electrical and heat isolation, which can non-specifically stimulate and damage the local brain regions. The
intensity, frequency, and duty cycle of light pulses from each fiber in the array was controlled independently using an inhouse
developed LabView based program interfaced with a microcontroller driving the individual LEDs. While the
temporal profile of the light pulses was controlled by varying the current driving the LED, the beam profile emanating
from each fiber tip could be sculpted by microfabrication of the fiber tip. The fiber array was used to stimulate neurons,
expressing channelrhodopsin-2, in different locations within the brain or retina. Control of neural activity in the mice
cortex, using the fiber-array based prosthetic, is evaluated from recordings made with multi-electrode array (MEA). We
also report construction of a μLED array based prosthetic for spatio-temporal stimulation of cortex.
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