LSD reshapes brain rhythms and complexity, sparing motor cortex

Key points

• LSD causes a genuine reduction in alpha and beta oscillatory power, distinct from shifts in peak frequencies.
• The drug flattens the aperiodic spectral slope and increases fractal dimension, indicating higher neural complexity.
• These changes are concentrated in sensory, language, emotion, and imagery networks, with minimal impact on motor cortex.
• Music does not amplify these neural effects and may actually attenuate them by grounding attention.
• Machine learning models identify peak-frequency shifts and complexity metrics as key markers of the psychedelic state.

Background

Previous research, including studies on psilocybin and DMT, established that psychedelics generally cause broadband desynchronization in the brain. However, it remained unclear whether this desynchronization was a true weakening of neural oscillations or merely a shift in their frequency. Additionally, while music is often used in psychedelic-assisted therapy to enhance emotional depth, its specific neurophysiological interaction with the drug state was not well understood. This study builds on earlier work by Carhart-Harris and colleagues, which first identified subtle alpha peak shifts under LSD, by providing a more comprehensive, spatially resolved map of these effects.

Why it matters

Understanding the precise electrophysiological mechanisms of psychedelics helps distinguish LSD from other drugs like psilocybin and DMT. This knowledge is crucial for developing psychedelic-assisted therapies, as it clarifies how the drug reorganizes brain dynamics to produce therapeutic effects. The finding that music may attenuate rather than amplify neural changes also has implications for clinical settings, suggesting that external stimuli might modulate the intensity of the psychedelic experience.

What to watch

Future research needs to disentangle the neuropharmacological mechanisms behind oscillatory power weakening and peak-frequency shifts. Larger studies are required to confirm the interaction between LSD and music, as the current sample size was too small to detect subtle effects reliably. Additionally, tighter alignment between neural activity and subjective experience is needed to better understand how these brain changes translate into the phenomenology of the psychedelic state.