Abstract
Stimulus selective delay period activity, which has been found in neurons throughout a wide range of cortical areas, including prefrontal, inferotemporal and parietal cortex, is considered a possible substrate of stimulus recall during working memory performance. Such activity has recently been found earlier in the visual system, in dorsal extrastriate cortical area MT. In the present study, we examined the delay period activity of V4 neurons while monkeys performed delayed matching of stimulus orientation. Most neurons showed decreased activity relative to pre-stimulus spontaneous firing during much of the delay period, and approximately 30% of the studied neurons showed orientation selective delay period activity. In some cells, stimulus selective delay period activity was observed even when presentation of the stimulus to be remembered was spatially remote from the recorded neuron's receptive field. These stimulus selective delay period responses suggest involvement of V4 neurons in cortical networks mediating working memory.
Supported by NIH grant P30 EY01319 and Research to Prevent Blindness.