Prefrontal Cortex and Consciousness: Beware of the Signals.

Abstract

During binocular rivalry (BR), incongruent, unchanged visual stimulation induces intrinsically generated transitions in conscious content. Due to this astonishing property, BR is commonly combined with functional magnetic resonance imaging (fMRI) or single neuron recordings to identify the neural correlates of consciousness (NCCs); namely, brain activity reflecting conscious contents and spontaneous transitions between them. No-report BR versions, where the perceived stimulus is decoded from objective markers like reflexive eye movements instead of active behavioral reports, can be used to discard activity related to motor and postperceptual processes that might contaminate the pure NCC. This is especially relevant for resolving an ongoing theoretical debate about the role of the prefrontal cortex (PFC) and posterior cortical areas in consciousness. Block recently suggested that no-report might still fail to eliminate postperceptual cognitive processes accompanying BR [1,2]. This could result in neural signals being incorrectly interpreted as reflecting conscious contents, under the strong assumption that postperceptual processes are systematically aligned to each of the competing percepts. He therefore calls for the development of no-post perceptual cognition paradigms and highlights the BR paradigm of Brascamp et al. [3], that uses unreportable transitions, to address this problem.We agree with Block that dissociating the NCCs from cognition is necessary. However, we caution against (i) Block’s interpretation of the Brascamp et al. findings; and (ii) the criticism that our recent recordings during no-report BR in the PFC reflect postperceptual cognitive processing and show no evidence of transition processes.