Fiber-optic sensor system for rapid positioning of a microelectrode array

A fiber-optic intensity sensor has been developed for vertically positioning microelectrode arrays above the retina of a live frog. Closely spaced fibers illuminate and collect reflections from the retinal surface, and the output is electronically processed to drive an automated positioning circuit. Experimental and theoretical evaluations of fiber types and separation for both specular and diffuse reflectors, in vitro and in vivo, are presented, and multimode fibers on 125-mum centers are chosen for retinal experimentation. The sensor has applications in assessing spatial selectivity of stimulation of a multielectrode array and may be adaptable for lateral positioning.