Hypothesis

Psilocybin‑induced desynchronization of the default mode network (DMN) creates a high‑entropy window that, when paired with enhanced slow‑wave sleep, activates glymphatic clearance of maladaptive synaptic proteins, enabling long‑term remodeling of DMN connectivity.

Mechanistic Rationale

• Acute psilocybin reduces functional connectivity within the DMN, especially between medial prefrontal cortex and posterior cingulate cortex, while increasing between‑network FC [1] [2].
• This desynchronization raises brain entropy >3× that of methylphenidate, a state linked to increased synaptic lability and openness to plastic change.
• Slow‑wave sleep (SWS) drives the largest glymphatic influx, clearing extracellular metabolites and protein aggregates such as phosphorylated tau and Aβ oligomers.
• We propose that the entropy‑driven lability tags synapses for removal; during ensuing SWS the glymphatic flux preferentially clears these tagged elements, thereby stabilizing a new, less rigid DMN configuration.
• Without sufficient SWS, the entropy window closes and the network reverts to its baseline configuration, explaining the fade of benefits by ~3 months.

Testable Predictions

1. Participants who receive psilocybin and subsequently show increased SWS power (0.5‑4 Hz EEG) will exhibit greater and more durable reduction in DMN‑mPFC/PCC FC at 1‑ and 3‑month follow‑ups compared with those who receive psilocybin alone.
2. Pharmacological suppression of SWS (e.g., low‑dose trazodone) after psilocybin will abolish the long‑term DMN FC changes despite preserved acute entropy.
3. Glymphatic MRI metrics (e.g., diffusion‑based perivascular space enlargement) will correlate positively with the magnitude of SWS increase and negatively with the persistence of DMN hyperconnectivity.

Experimental Design

• Sample: 60 medication‑free adults with moderate‑to‑severe depression, randomized to three arms (psilocybin + sleep enhancement, psilocybin + placebo sleep, active control + sleep enhancement).
• Sleep enhancement: nocturnal acoustic closed‑loop stimulation timed to up‑state phases to boost SWS power by ~20 % (validated in prior work).
• Outcomes: resting‑state fMRI DMN FC at baseline, 24 h, 1 week, 1 month, 3 months; high‑density EEG SWS power; glymphatic imaging via intrathecal contrast‑enhanced MRI or ALS‑pulsatile arterial spin labeling.
• Analysis: mixed‑effects models testing arm × time interactions; mediation analysis to test whether SWS increase mediates the relationship between psilocybin and DMN FC change; falsification criterion – if no significant arm × time interaction for DMN FC at 3 months, the hypothesis is refuted.

This framework links acute psychedelic neurodynamics to a homeostatic sleep‑clearance process, offering a concrete, falsifiable route to explain why some patients retain benefits while others do not.