Figure 7.

Multisite patterned glutamate injections through the prototype synapse chip device elicit RGC responses in patterns resembling the injection patterns. (a–c) Two dimensional color histogram plots depicting the spread of somal RGC responses (warmer colors representing larger numbers of responsive cells) to glutamate injections through a select set of microports simultaneously representing pixelated dot patterns of characters ‘I’, sideways and inverted ‘L’ and sideways ‘T’, respectively. In each plot, the inset at the upper right corner shows the corresponding glutamate injection pattern (forms represented by small gray squares) and the responses are overlaid with the device microports (active microports represented by yellow circles and inactive microports represented by red circles) and the 60 electrodes of the MEA (the black dots at the intersections of the 8×8 dashed grid lines, with the exception of the four corner intersections, represent the locations of the 60 electrodes). By visual inspection of the RGC response plots and consideration of patterns formed by warmer colors in each plot, RGC response patterns with high correspondence to the glutamate injection patterns can be readily discerned, thus confirming successful patterned stimulation of the retina with glutamate.