Real-time Characterization of Neuronal Response for Selective Stimulation

Spatiotemporal selectivity of extracellular stimuli is a significant challenge in the development of neural interfacing devices. Although models have previously been used to investigate responses to various stimulus waveforms, it is of significant interest to experimentally validate the stimulus-evoked cellular response and use that information to optimize the stimulus patterns. To address these challenges, we have developed a highthroughput closed-loop system of multisite stimulation and recording that facilitates the characterization of the cellular activity evoked by extracellular stimulation. We explore excitatory waveforms applied to cortical networks at multiple sites in a multi-electrode array (MEA) to achieve increased precision and localization of extracellular stimuli. We measure the response of all individual neurons using fluorescent calcium-sensitive dyes in conjunction with novel real-time optical processing algorithms and an automated data acquisition platform. Using this system, we have characterized waveforms that excite neural activity within a 400μm X 400μm field of view, and in this work we investigate the use of such waveforms to explicitly direct the focus of an extracellular stimulus.