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Abstract:
Binocular rivalry (BR) has been successfully combined with extracellular electrophysiological recordings in awake, behaving macaques to study the cortical mechanisms of visual conscious experience. The contribution of different cortical areas to visual awareness is commonly determined by reporting the percentage of neurons modulated, in each area, in accordance with the percept. However, in order to obtain a detailed understanding of the cortical mechanisms mediating subjective visual perception it is likely that valuable insights could be gained by studying the neuronal interactions within pools of neurons sharing similar stimulus preference. One of the most commonly studied forms of neuronal interaction is noise (or spike count) correlations i.e the correlation in the variability around the mean of trial by trial spike counts between pairs of simultaneously recorded neurons. In this study we used binocular flash suppression (BFS), a highly controlled variant of BR, to explore the neuronal correlates of visual awareness in the inferior prefrontal convexity (icPFC) of the macaque brain while simultaneously recording pairs of neurons preferring the same visual stimulus. We report that the perception of a stimulus under rivalrous conditions is accompanied by a drastic decrease in noise correlations between neurons sharing a similar preference to this stimulus compared to noise correlations when the same stimulus is perceived without competition. We propose that this decorrelation of neuronal discharges during visual competition is optimal for rivalrous perception since it renders the dominant neural population representing the perceived stimulus more sensitive to it by increasing the signal to noise ratio conveyed by signal averaging. This is in agreement with local correlation models that predict enhanced information coding as a result of decorrelated noise between neurons with similar tuning functions. Similar studies in other visual cortical areas during rivalrous visual stimulation could show whether reduction of correlated noise is observed throughout the ventral visual stream or it is a unique property of the ventral prefrontal cortex.
