From Siegel et al (open source).:
A single dose of psilocybin, a psychedelic that acutely causes
distortions of space–time perception and ego dissolution, produces rapid
and persistent therapeutic effects in human clinical trials1,2,3,4. In animal models, psilocybin induces neuroplasticity in cortex and hippocampus5,6,7,8.
It remains unclear how human brain network changes relate to subjective
and lasting effects of psychedelics. Here we tracked
individual-specific brain changes with longitudinal precision functional
mapping (roughly 18 magnetic resonance imaging visits per participant).
Healthy adults were tracked before, during and for 3 weeks after
high-dose psilocybin (25 mg) and methylphenidate (40 mg - a placebo in the form of methylphenidate, (Ritalin)), and brought
back for an additional psilocybin dose 6–12 months later. Psilocybin
massively disrupted functional connectivity (FC) in cortex and
subcortex, acutely causing more than threefold greater change than
methylphenidate. These FC changes were driven by brain desynchronization
across spatial scales (areal, global), which dissolved network
distinctions by reducing correlations within and anticorrelations
between networks. Psilocybin-driven FC changes were strongest in the
default mode network, which is connected to the anterior hippocampus and
is thought to create our sense of space, time and self. Individual
differences in FC changes were strongly linked to the subjective
psychedelic experience. Performing a perceptual task reduced
psilocybin-driven FC changes. Psilocybin caused persistent decrease in
FC between the anterior hippocampus and default mode network, lasting
for weeks. Persistent reduction of hippocampal-default mode network
connectivity may represent a neuroanatomical and mechanistic correlate
of the proplasticity and therapeutic effects of psychedelics.