Microstimulation-evoked neural responses in visual cortex are depth dependent

BackgroundCortical visual prostheses often use penetrating electrode arrays to deliver microstimulation the cortex. To optimize placement within cortex, neural responses at different cortical depths must first be understood.ObjectiveWe investigated how evoked by in cortex varied with depth, of both stimulation and response.MethodsA 32-channel single shank array was inserted into primary anaesthetized rats, such that it spanned all layers. Microstimulation currents up 14 μA (single biphasic pulse, 200 μs per phase) applied spanning 1600 μm, while simultaneously recording activity on channels a response window 2.25–11 ms.ResultsStimulation elicited elevated neuronal firing rates Compared deep sites, superficial sites responded higher given current had lower thresholds. The laminar spread across depth depended line anatomical models.ConclusionStimulation layers evokes local lowest thresholds, most column. In conjunction perceptual reports, these data suggest optimal for has electrodes positioned 2/3, top layer 5.