P3b-like Responses In Newborns And Fetuses As Possible Evidence Of Consciousness

Abstract of the talk:
The developmental stage at which consciousness emerges is uncertain. Given that fetuses and infants cannot answer questions or self-report their conscious state, neural markers of consciousness are perhaps crucial to investigating the possibility of subjective experience in the perinatal period. In particular, the P3b or late slow wave (LSW) component is a cortical evoked signal associated with a reorienting of attention and possibly conscious processing, which can be recorded noninvasively with magnetoencephalography (MEG).
Thus, to investigate the possibility of perinatal consciousness, our research group recorded cortical MEG responses to auditory irregularities in fetuses and newborns. Specifically, we utilized the auditory local global paradigm introduced by Bekinschtein et al. (2009 PNAS) to test for evidence of Bayesian prediction errors in fetuses and newborns. This paradigm involves auditory irregularities (i.e., low probability “oddball” stimuli) both within-trials (“local violations”) and between-trials (“global violations”).
While it is arguable that the brain might process local rule violations unconsciously, cortical responses to global rule violations are stronger evidence of consciousness. We found that fetuses and newborns showed a clear LSW (analogous to the adult P3b response), indicating hierarchical rule learning. Notably, this response was limited to active behavioral states, consistent with an explanation that the fetuses and newborns do not recognize global rule violations when they are in quiet sleep. Although these findings are highly suggestive of perinatal consciousness, the sensitivity and specificity of the P3b response has been questioned; thus, future work should also look at alternative markers such as MEG signal entropy or perturbational complexity.