Attentional modulation in primate visual area V4

Selective attention has previously been shown to significantly alter firing rates in visual area V4 of rhesus macaques performing cued target detection tasks. To account for these effects, two main models have been introduced: a model of attention as an increase in stimulus contrast, and a model of attention as a multiplicative resealing of the unattended response. This dissertation adds to the studies that developed these models of attention by incorporating time-varying response properties. Several new approaches are taken to quantify the effects of attention on visual processing in V4, including close consideration of the effects of attention on response dynamics. The inclusion of response dynamics in the analysis leads to the rejection of both models as partially correct, but incomplete.; By developing several new approaches to analyzing transient visual responses, this dissertation investigates the temporal patterning of neuronal firing in response to transient visual stimulation in V4, and shows that attention is capable of altering the timing of spikes in visual responses, even when the spike count response is not significantly modulated. These timing effects include changes in the amount of power time-locked to the stimulus cycle and changes in response latency. These effects of attention are distinguishable from, but overlap with the effects of, an increase in stimulus contrast and a multiplicative scaling of the response.