Bifurcation in brain dynamics reveals a signature of conscious processing independent of report

The same auditory stimulus can produce either sustained or brief brain activity around 250–300 milliseconds after the sound, even when people are not performing any task. This bifurcation in electroencephalographic dynamics predicts whether people later report having consciously perceived the stimulus, both when they are asked to report on a task and when their conscious contents are sampled randomly during passive listening. Source localization shows that task-free conscious access engages the same neural networks as explicit report, except for frontal executive components. Studying variability in brain dynamics may help identify the core signatures of conscious access independently of decision or report processes.

Study at a glance

Abstract

An outstanding challenge for consciousness research is to characterize the neural signature of conscious access independently of any decisional processes. Here we present a model-based approach that uses inter-trial variability to identify the brain dynamics associated with stimulus processing. We demonstrate that, even in the absence of any task or behavior, the electroencephalographic response to auditory stimuli shows bifurcation dynamics around 250–300 milliseconds post-stimulus. Namely, the same stimulus gives rise to late sustained activity on some trials, and not on others. This late neural activity is predictive of task-related reports, and also of reports of conscious contents that are randomly sampled during task-free listening. Source localization further suggests that task-free conscious access recruits the same neural networks as those associated with explicit report, except for frontal executive components. Studying brain dynamics through variability could thus play a key role for identifying the core signatures of conscious access, independent of report. Current knowledge on the neural basis of consciousness mostly relies on situations where people report their perception. Here, the authors provide evidence for the idea that bifurcation in brain dynamics reflects conscious perception independent of report.