Assessment of stereopsis in rhesus monkeys using visual evoked potentials

Rhesus monkeys can have deficiencies in stereo vision, making it necessary to screen monkey subjects intended for single cell studies of stereo-based depth processing. We measured VEPs in two monkeys using a dynamic random-do t display in which a stereo-defined checkerboard reversed in depth. Monkeys fixated upon a small dot during stimulus presentation. One monkey showed c lear evoked potentials in response to changes in disparity that were simila r to those obtained in human subjects, using an identical stimulus paradigm . Controls with presentations of the monocular stimulus sequences (in which no depth reversal can be perceived) yielded no or much weaker VEPs. In the other animal, however, there was no difference in evoked potential between the two conditions. These electrophysiological findings closely match the performance of these same two subjects in a disparity discrimination task i n which they were previously trained. We conclude that VEPs using this type of stimulus disp lay can be used to screen monkeys for single cell or beha vioral studies of stereopsis.