If no stimulus change occurred within 5000 ms, the monkey was rewarded simply for maintaining fixation. These catch trials were not included for analysis. We manipulated spatial and feature attention by cueing the monkey in blocks as to which of the two stimuli was more likely to change (spatial attention) and which feature would change (feature attention). Before each block of trials, the monkey performed 10

instruction trials in which only a single stimulus appeared in the location and with the type of change (orientation or spatial frequency) that would change most often in the upcoming block of trials. Instruction trials were not considered in the analysis. Of the 125 trials per block, 25 randomly interleaved trials contained changes in the uncued stimulus. Only one stimulus change occurred in each trial, and the monkey was rewarded for correctly detecting a change in either stimulus, Everolimus purchase regardless of the cued location.

We only included data sets for which the monkey completed at least four blocks of each spatial and feature attention condition and achieved at least 90% correct detections of the easiest orientation and spatial frequency changes. Importantly, the stimuli preceding the orientation or spatial frequency change were the same on every trial throughout an entire day of data, regardless of the attention condition or eventual stimulus change. We were interested in the effects of attention independent of sensory responses. We therefore focused our analyses on the stimulus presentation immediately

before the change because the mTOR inhibitor review stimuli were the same at this point on every the trial and because the monkey’s attentional state at this time was most likely to affect his ability to successfully detect the upcoming change. All of the primary analyses are based on spike count responses calculated from the period between 60 and 260 ms after stimulus onset. We obtained tuning data for all of the neurons we recorded by measuring responses to a variety of Gabor stimuli either before or after the primary experiments each day. The monkeys performed a single stimulus version of the usual orientation change detection task on a stimulus in the upper visual field (far outside the receptive fields of the neurons under study). At the same time, we synchronously flashed an additional Gabor stimulus in the lower visual field in each hemifield for 100 ms each. The test Gabors had the same size and location as the Gabors in the main attention task that day. We varied either the orientation of the test Gabors while keeping the spatial frequency the same as in the orientation change detection task or the spatial frequency while keeping the orientation the same as in the spatial frequency change detection task. We constructed multidimensional tuning curves using spike count responses during the period from 60 to 160 ms after stimulus onset.