Cortex-wide Dynamics of Internal Decisions About Behavioral Context.

Many human decisions manifest in the outside world as motor actions. Correspondingly, neural signals reflecting decision formation are expressed in neural populations encoding the final action. Some decisions, however, are internal, shaping overt behavior indirectly through the selection of policies or rules that guide elementary sensory-motor decisions. We studied the human brain dynamics underlying internal decisions about the stimulus-response mapping rule for reporting visual orientation judgments. The rule changed unpredictably in a hidden fashion, and participants tracked it by accumulating ambiguous sensory cues. Computational model-based decoding of source-level magnetoencephalography data uncovered representations of the internal belief about the active rule in many areas, including occipital cortex. These representations exhibited profiles as predicted by normative models and as observed in action-related frontal areas during overt decisions. We conclude that a widely distributed network of cortical areas implements evidence accumulation for internal decisions, and that even visual cortex may represent high-level beliefs.