The hallucinogenic drug psilocybin, which activates serotonin receptors, selectively impairs the ability to perceive coherent motion in random dot patterns, a task that relies on high-level global motion detectors, while leaving contrast sensitivity for drifting gratings, mediated by low-level detectors, unaffected. This pattern of visual processing deficits mirrors those seen in schizophrenia, suggesting psilocybin may serve as a pharmacological model for studying psychosis and the neural basis of visual perception.
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.