Perceptual experiences are shaped by prior events, as argued by Predictive Processing and Active Inference frameworks. This paper examines how such experiences begin before birth, within the womb. A key but often neglected point is that humans develop inside another human body, a universal experience. The authors focus on the emergence of minimal selfhood in utero as a process of co-embodiment and co-homeostasis, emphasizing their interdependence. They conclude by discussing implications for debates on conscious experience, the minimal self, and social cognition.
Consciousness likely cannot begin before the establishment of thalamocortical connectivity at 26 weeks gestation, as this system is necessary for subjective experience according to most theoretical frameworks. To determine when consciousness emerges after this point, the authors advocate developing a sensory perturbational complexity index (sPCI) using auditory, visual, or olfactory cortical perturbations—rather than electromagnetic ones—to estimate the perinatal brain's state of consciousness. Techniques such as fMRI, EEG, and MEG can be used in both newborn and fetal studies, with the womb offering a more controlled environment than the cradle for such investigations.
Fetuses in the last trimester of pregnancy show signs of hierarchical rule learning, a cognitive ability linked to conscious processing. Using fetal magnetoencephalography on 56 healthy fetuses between gestational weeks 25 and 40, an auditory oddball paradigm with first- and second-order regularities was presented. Brain responses to standard versus deviant tones indicated formation of a memory trace for the second-order regularity, an ability that develops with physiological brain maturation and was reliably present only in fetuses older than week 35. Autonomic nervous system activity, replicating findings in newborns, showed the importance of activity state for cognitive processes. These results support the assumption that fetuses in the last weeks of gestation can consciously process stimuli from outside the womb.
Information-based metrics of neural activity can help quantify consciousness before and shortly after birth. Using fetal magnetoencephalography (fMEG) in human fetuses and neonates, researchers evaluated measures of entropy, compressibility, and fractality. Lempel-Ziv-Complexity (LZC) was the most practical metric because it is unequivocal and requires low computational effort, whereas fractality and entropy measures need more parameter adjustments. Comparing a brain-activity channel with a control channel in neonates showed significant differences in most complexity metrics, serving as proof of concept. For fetal data, results were less clear, possibly due to leftover maternal signals. The inconsistency across metrics highlights challenges in using complexity metrics as neural correlates of consciousness.