LSD Reconfigures Cortical Dynamics Through Faster Brain Rhythms and Increased Fractal Dimension (Subramani et al., Communications Biology 9:1244, 2026)

Subramani, Nest, Pascarella, Brunel, Mantilla Ramos, Harel, Muthukumaraswamy, Carhart-Harris, Lioi, Farrugia and Jerbi re-analyze magnetoencephalography (MEG) data from 17 participants, originally collected by Carhart-Harris and colleagues, under a within-subject, single-blind, counterbalanced design: each participant received intravenous LSD (75 μg) and placebo (saline) on separate days 14 days apart, with eyes-closed resting recordings both with and without music. Sent by PDF on Telegram.

The question

Psychedelics are known to weaken alpha and beta brainwave power, a pattern usually read as cortical "desynchronization." But a weaker oscillation and an oscillation that simply shifted to a different frequency look the same in a standard frequency-band analysis. The paper asks whether LSD's effect on alpha/beta power is genuine, or an artifact of frequencies moving without lost strength.

What they found

Both are true, and separable. Using spectral parametrization to isolate true oscillatory peaks from the broadband (aperiodic) spectrum, LSD produces:

Genuine power loss, not just an artifact: oscillatory activity weakens from theta through beta (up to 30 Hz), while mid-gamma power (60–90 Hz) significantly increases.
Faster peak frequencies: alpha and beta oscillations shift upward in frequency under LSD, a pattern noted in a few prior studies but not previously quantified or mapped spatially region by region. Ignoring this shift and analyzing fixed frequency bands inflates the apparent effect, so prior desynchronization findings may overstate how much oscillations actually weakened.
A flatter aperiodic (1/f) spectral slope, plus increased neural signal fractality and complexity, concentrated in sensory, language, emotion and imagery-related networks and absent from motor cortex.
Spatial dissociation: alpha-power reduction concentrates in temporal regions; beta-power reduction is widespread across the cortex; high-gamma reduction concentrates posteriorly. Effects that appeared in the posterior cingulate cortex under naive band-power analysis disappeared once peak shifts were accounted for, meaning that apparent effect was an artifact of the frequency shift.
Supervised machine learning, used to cross-check the inferential statistics rather than as the main method, finds peak-frequency shift, aperiodic slope and complexity measures are the strongest discriminators between LSD and placebo states.
Music does not amplify these neural signatures, and shows a non-significant trend toward dampening them instead, counter to a plausible expectation that music would deepen a psychedelic state's neural signature.

Why the method matters beyond this drug

The paper's methodological point generalizes past LSD: any study inferring "desynchronization" from band-limited power alone cannot distinguish a weaker oscillation from a faster one, and the two have different implications for what the drug is doing to the underlying neural circuit. Separating periodic from aperiodic spectral components, and peak frequency from peak power, is presented as the fix.

Limits, in the authors' own account

n = 17, a secondary analysis of data not collected for this question. Phenomenological ratings were taken near peak drug effect, but MEG recording happened roughly 150 minutes after peak effect, a mismatch the authors say likely weakens any brain-phenomenology correlation. Region-resolved regressions are flagged as exploratory given sample size and multiple comparisons. High-gamma peak estimation is called less reliable than alpha/beta because gamma oscillatory structure is less consistent across subjects and regions.

Tier

T1 — peer-reviewed primary research in Communications Biology (Nature Portfolio), read in full from the PDF (pypdf extraction; author-name diacritics render imperfectly in the raw text layer). No published: day is stated beyond the 2026 volume/issue (9:1244); recorded at year precision rather than guessed.

karim-jerbi · robin-carhart-harris · free-will · determined · synthesis