Artificial neural networks built with feedback connections from multisensory to unisensory cortices, consistent with all-or-none models of conscious access, produced intermediate reaction times when multisensory stimuli were associated with unisensory feedback. In psychophysical testing with 29 subjects completing 10 hours of a multisensory cue-congruency task, reaction times to multisensory cues reported as unisensory fell between those of fully aware and fully unaware cues. These results suggest that graded forms of phenomenal consciousness can arise from neural networks that follow all-or-none principles.
Conscious experience includes not only awareness of external objects but also a sense of the embodied self, which relies on integrating multisensory stimuli near the body, a process involving the Peripersonal Space (PPS) system. Using high-density EEG in awake participants, a neural marker of PPS—high-beta oscillations in centroparietal regions during audiotactile integration near versus far from the body—was identified. This marker persisted during dreaming and waking conscious states but was absent during dreamless, unconscious states. In patients with disorders of consciousness, the same index predicted behavioral measures of consciousness and clinical outcome, suggesting that multisensory integration within PPS is tightly linked to conscious experience.
A neural marker based on high-beta oscillations measured during a simple audiotactile task can detect consciousness and predict recovery in patients with disorders of consciousness. The marker, derived from the peripersonal space system, was present in healthy participants during wakefulness and dreaming but absent in dreamless sleep. In 72 patients with disorders of consciousness, the marker correlated with behavioral measures of consciousness and predicted recovery at discharge. The marker was also associated with forebrain mesocircuit integrity, suggesting a bedside-compatible tool for detecting covert consciousness and guiding clinical decisions in unresponsive patients.
Convergent neurons—those that receive input from multiple sources but do not integrate that information—more readily exhibit properties of consciousness than integrative neurons, contrary to the predictions of integrated information theory. In nonhuman primates under propofol anesthesia, convergent neurons showed greater neural complexity and noise correlation, and were more impacted during loss of consciousness. Neural ignition, the coactivation of primary somatosensory and ventral premotor cortex on the same trial, was more frequent in conscious states, supporting the global neuronal workspace theory. The findings directly contrast two major theories of consciousness within a single dataset.