Precisely patterned optogenetic stimulation with mini-LED array and lens optics in rodent visual cortex

Abstract

Optogenetic implants promise higher resolution and more specific neural targets than electrical ones. Higher resolution realized by smaller luminance emission diode (LED) often face relatively low luminance intensity, narrow working distance, and high fabrication cost. Utilizing lens-optics can achieve collimation of luminescence and broader working distance by combining cheaper LED elements. Here we demonstrate a prototype of micro-photo-stimulator system consisting of mini-LED (8 x 8 pixels in 20 x 20 mm, 2.8 mm pitch) and two convex lenses (biconvex and pleno-convex lens). We then tested micro-photo-stimulation of the system and recorded physiological responses to the photo-stimulation. We injected AAV-DIO-eNpHR3.0 in V1 monocular region of Parvalbmin-cre rats, or AAV-CaMK2-chrimsonR in same area of wild-type rats. The micro-photo-stimulation system was installed over the V1 area exposed surgically under anesthetized, head fixed conditions. The stimulation resolution significantly improved (around 0.5 to 0.8 mm) with relatively remained intensity (> 20 mW/mm2). Electrophysiological recording by silicon probes equipping multiple recording sites confirmed photo-evoked responses in highly restricted area.