A neuroimaging study has found that LSD not only weakens conventional brain waves but also accelerates them and raises the complexity of neural signals, with the strongest effects in regions involved in sensory processing, language, emotion and mental imagery. Movement-related areas appeared largely spared. The findings, published in Communications Biology, also touch on how listening to music might modulate these drug-induced changes, though that aspect did not hold under strict statistical correction.
LSD is a potent psychedelic that temporarily alters perception, mood and self-awareness. Like other classic psychedelics, it largely acts on serotonin 2A receptors, though it also binds to dopamine receptors. Understanding how the drug reshapes large-scale brain activity helps scientists probe the biological roots of conscious experience.
Researchers used magnetoencephalography, or MEG, to track the brain’s rapid electrical activity in a non-invasive setting. In MEG, a participant sits with their head inside a helmet-like scanner containing sensitive magnetic detectors that register the tiny fields produced as groups of neurons fire together.
The study analysed two main signal types: rhythmic brain waves and non-rhythmic background activity. Resting alpha waves cycle at about 8 to 13 times per second, while beta waves run around 15 to 30 Hz and relate to active thinking; background activity typically diminishes at higher frequencies.
Past psychedelic research has consistently shown a broad drop in alpha and beta wave strength, a phenomenon known as cortical desynchronization. But traditional analyses can conflate a change in wave speed with a loss of strength, or mistake shifts in background activity for genuine oscillations, making it hard to separate true desynchronisation from spectral peak shifts.
To address this, the researchers separated rhythmic activity from background signals and tracked the exact peak frequencies of alpha and beta waves rather than fitting them into fixed frequency windows. They computed Lempel-Ziv complexity and Higuchi fractal dimension to gauge signal unpredictability and roughness across time, and used machine learning to identify features most able to distinguish LSD from a placebo state.
Four hours after an intravenous dose of 75 micrograms of LSD, 17 healthy volunteers underwent MEG scans in two seven-minute conditions: eyes closed in silence, and eyes closed with ambient music. Each participant underwent both LSD and placebo sessions in a randomised, single-blind, cross-over design separated by 14 days.
When rhythmic waves were separated from background activity and peak shifts accounted for, alpha and beta weakening persisted as a genuine feature of LSD. Alpha desynchronisation was most pronounced in the temporal lobes, while beta desynchronisation occurred broadly across the cortex, a finding that clarifies previous interpretations of widespread slowing.
“A characteristic effect of classic psychedelics is the desynchronization of rhythmic brain activity (that is, reduced coordination of activity among neural populations) in the alpha (8-13 Hz) and beta (15-30 Hz) bands,” Subramani told PsyPost. “LSD, however, appears somewhat unique because it also speeds up these intrinsic oscillations, by up to 2 Hz for alpha and up to 5 Hz for beta. This acceleration creates an ambiguity: it is unclear whether LSD genuinely desynchronizes these rhythms, or whether the previously reported desynchronization is an artifact of shifts in the spectral peaks.”
Further analysis showed altered activity in the posterior cingulate cortex, a hub linked to self-reflection. In traditional analyses that mix signals, this region showed large drops in wave power under LSD; after removing background activity, the rhythmic differences largely disappeared, suggesting LSD mainly perturbs non-rhythmic activity there.
In addition to weakening the waves, LSD sped them up across large brain areas. On average, alpha peak frequency rose by about 2 Hz, while beta peaks shifted upward by around 5 Hz. Machine learning models based on these peak shifts correctly identified LSD versus placebo in excess of 82 per cent of cases, well above chance.
The researchers also found the brain’s background activity flattening, with reduced slow activity relative to faster activity. They reported substantial increases in Lempel-Ziv complexity and fractal dimension, especially in visual areas at the back of the brain. Models using these complexity and fractal measures distinguished LSD from placebo with more than 76 per cent accuracy above chance.
“In plain terms, LSD makes the brain’s main rhythms faster and weaker, and makes its activity more complex,” Subramani noted.
The findings echo earlier PsyPost coverage of brain activity under microdoses and full psychedelic doses, and align with other recent work suggesting a shift away from slower rhythms under psychedelics. The authors acknowledge that the speeding of alpha and beta rhythms has not consistently been observed with other psychedelics such as psilocybin.
Looking at the broader picture, the team mapped LSD’s effects onto a large database of more than 14,000 prior brain-imaging studies and found the drug’s impact followed distinct functional hierarchies across brain networks. Reductions in alpha and beta strength, background flattening and rising complexity were strongest in networks tied to vision, hearing, language, emotion and mental imagery, while motor areas remained largely unaffected.
When it came to music, the results did not survive rigorous multiple-comparisons corrections across the whole brain. However, uncorrected trends suggested the opposite of the researchers’ initial expectation: listening to music tended to dampen the LSD effects, rather than amplify them, potentially acting as an external anchor for the brain’s activity.
“Music can be very emotionally powerful, and music and psychedelics have been used together in rituals across many cultures,” Subramani said. “We wanted to formally test how music modulates the way LSD affects the brain. We hypothesized that music potentiates the effect of the drug. Somewhat surprisingly, and albeit not statistically robust, we found the opposite trend: music appeared to reduce the drug effect, which could suggest that the stimulus acts as an anchor that keeps subjects from fully experiencing the psychedelic state.”
He cautioned that the music result is exploratory and should not be over-interpreted, describing the finding as hypothesis-generating and noting the study’s limited sample size of 17 participants.
Limitations include the modest number of volunteers, which reduces statistical power for subtler interactions between the drug and external factors like music, and the timing of the scans—around four hours after injection, by which point subjective effects had largely peaked. The seven-minute music condition also captures only a snapshot of a dynamic auditory experience.
Looking ahead, the team plans larger studies and finer-grained designs to probe how these faster rhythms relate to other measures of brain communication, such as functional connectivity. They are also extending their analytic approach to examine how the changes in oscillatory speed and complexity relate to broader network dynamics, with a preprint expected soon.
The study, titled LSD reconfigures cortical dynamics through faster brain rhythms and increased fractal dimension, lists Venkatesh Subramani and Karim Jerbi among its senior authors, with further contributions from Timothy Nest, Annalisa Pascarella, Jérémy Brunel, Yorguin José Mantilla Ramos, Yann Harel, Suresh Muthukumaraswamy, Robin Carhart-Harris, Giulia Lioi and Nicolas Farrugia.
