Neurophysiological substrates of visual awareness in the macaque prefrontal cortex

Human fMRI studies during binocular rivalry have demonstrated an involvement of prefrontal cortex (PFC) in the processing of subjective visual perception. In this study we used binocular flash suppression, a version of binocular rivalry that permits the robust induction of a visual percept, to study the neuronal correlates of visual awareness in the macaque prefrontal cortex (PFC) and specifically in the inferior prefrontal convexity. We found that the firing rate of almost 70 of the visually selective neurons closely followed the induced visual percept. This percentage is significantly higher than the respective percentage of perceptually modulated cells found in the striate and extrastriate visual cortex (V1, V2 and V4) but smaller than that found in the inferior temporal cortex (IT) (almost 90). Interestingly, we observed that the neuronal responses following a perceptual alternation were transient, similar to the transient BOLD response observed during perceptual transitions in the human binocular rivalry fMRI studies. Our finding provides further evidence in support of a role of higher brain areas in processing an explicit perceptual representation during ambiguous visual stimulation. In addition, it points to a potential neuronal network consisting of perceptually modulated cells in IT and PFC that process an explicit representation of a visual percept. The existence of such a network is not surprising since area TE of inferior temporal cortex is anatomically connected to the inferior convexity (areas 12/45) through feedforward and feedback pathways. Finally, in an effort to explore whether the perceptual modulation observed in primary visual cortex (V1) is influenced by a feedback signal from PFC we will also present data from simultaneous PFC and V1 neurophysiological recordings during binocular flash suppression