Spontaneous brain activity exhibits coherent oscillations across a wide range of frequencies, with temporal patterns highly correlated across distributed cortical areas, forming resting state networks. This work introduces harmonic brain modes as fundamental building blocks of complex spatiotemporal neural activity, defined as harmonic modes of structural connectivity (connectome harmonics) that yield fully synchronous activity patterns with different frequency oscillations constrained by brain structure. This framework links space and time in brain dynamics. The authors show how harmonic brain modes explain neurophysiological, temporal, and network-level changes across mental states (wakefulness, sleep, anesthesia, psychedelic). Spatial and temporal characteristics emerge from the interplay between excitation and inhibition, fitting changes associated with different mental states, offering tools for understanding brain dynamics in various states of consciousness.
As psychedelic therapy becomes more widely legalized, a note of warning is raised about recent reports that people with aphantasia—those lacking a mind's eye—have acquired visual mental imagery after using psychedelics. While gaining or increasing visual imagery may seem appealing, strong mental imagery is linked to several mental health conditions. The potential impact of switching on visual imagery in aphantasics or increasing its strength in neurotypical individuals remains unknown. The authors advocate for greater awareness of these risks and their ethical implications, especially concerning informed consent.
Activity in the primary visual cortex is thought to be closely linked to conscious visual experience, including mental imagery. In people with aphantasia, who lack visual imagery entirely, researchers examined brain activity during attempts to imagine. Neural patterns representing imagined content could be decoded equally well in both groups, but in aphantasia the signals were located on the same side of the brain as the stimulus and could not be matched to perceptual brain patterns. Additionally, the brain response to actual visual input was weaker in aphantasia. These findings suggest that imagery-related representations exist in primary visual cortex even without conscious visual experience, challenging the assumption that such activity necessarily produces sensory qualia.