Beyond task response-Pre-stimulus activity modulates contents of consciousness.

Conscious perception depends not only on brain activity after a stimulus appears but also on the brain's ongoing, spontaneous activity before the stimulus. Reviewing recent findings, the authors show that pre-stimulus alpha power (a measure of brain oscillations) influences how vividly or confidently people experience a stimulus, while trial-to-trial variability in alpha activity before and after the stimulus shapes conscious content. The key proposal is that pre- and post-stimulus activity interact in a non-additive, not merely additive, way within the alpha frequency band, and this interaction operates across multiple levels from neurophysiology to phenomenology. This perspective aligns with the Temporo-spatial theory of consciousness, emphasizing that understanding consciousness requires examining brain activity across wider timescales.

Study at a glance

Abstract

The current discussion on the neural correlates of the contents of consciousness (NCCc) focuses mainly on the post-stimulus period of task-related activity. This neglects the substantial impact of the spontaneous or ongoing activity of the brain as manifest in pre-stimulus activity. Does the interaction of pre- and post-stimulus activity shape the contents of consciousness? Addressing this gap in our knowledge, we review and converge two recent lines of findings, that is, pre-stimulus alpha power and pre- and post-stimulus alpha trial-to-trial variability (TTV). The data show that pre-stimulus alpha power modulates post-stimulus activity including specifically the subjective features of conscious contents like confidence and vividness. At the same time, alpha pre-stimulus variability shapes post-stimulus TTV reduction including the associated contents of consciousness. We propose that non-additive rather than merely additive interaction of the internal pre-stimulus activity with the external stimulus in the alpha band is key for contents to become conscious. This is mediated by mechanisms on different levels including neurophysiological, neurocomputational, neurodynamic, neuropsychological and neurophenomenal levels. Overall, considering the interplay of pre-stimulus intrinsic and post-stimulus extrinsic activity across wider timescales, not just evoked responses in the post-stimulus period, is critical for identifying neural correlates of consciousness. This is well in line with both processing and especially the Temporo-spatial theory of consciousness (TTC).