Prefrontal cortex neurons reflecting reports of a visual illusion

When a small, focally attended visual stimulus and a larger background fram e shift location at the same time, the frame's new location can affect spat ial perception. For horizontal displacements on the order of 1-2 degrees, w hen the frame moves more than the attended stimulus, human subjects may per ceive that the attended stimulus has shifted to the right or left when it h as not done so. However, that misapprehension does not disable accurate eye movements to the same stimulus. We trained a rhesus monkey to report the d irection that an attended stimulus had shifted by making an eye movement to one of the two report targets. Then, using conditions that induce displace ment illusions in human subjects, we tested the hypothesis that neuronal ac tivity in the prefrontal cortex (PF) would reflect the displacement directi ons reported by the monkey, even when they conflicted with the actual displ acement, if any, of the attended stimulus. We also predicted that these cel ls would have directional selectivity for movements used to make those repo rts, but not for similar eye movements made to fixate the attended stimulus . A population of PF neurons showed the predicted properties, which could n ot be accounted for on the basis of either eye-movement or frame-shift para meters. This activity, termed report-related, began approximately 150 ms be fore the onset of the reporting saccade. Another population of PF neurons s howed greater directional selectivity for saccadic eye movements made to fi xate the attended stimulus than for similar saccades made to report its dis placement. In view of the evidence that PF functions to integrate inputs an d actions occurring at different times and places, the present findings sup port the idea that such integration involves movements to acquire response targets, directly, as well as actions guided by less direct response rules, such as perceptual reports.