Consciousness & imagination

DMT N-dimethyltryptamine (DMT) is the psychoactive ingredient in ayahuasca. The relatively short duration of its effect is convenient for fMRI studies such as this. (Imperial College lay article here.) The results bear on neural processes that support conscious experience and imagination.

DMT (and psychedeledics generally) appear to dysregulate activity in the transmodal association cortex pole (TOP). This highest-level cortical network co-evolved with late expansions of the cerebellum in primates and especially in humans. The unimodal sensory areas are at the lower end of a hierarchical gradient of cortical organization; the TOP at the upper end is concerned with abstract perceptions and is active in imagination. The sensory-association cortex gradient develops in adolescence (more detail here).

Injection of DMT results in increased ‘global functional connectivity’ and communication across the brain between different areas and systems, together with ‘network disintegration and desegregation’, especially dysregulation of the TOP.

Administration of DMT (and presumably psychedelics generally)

  • decreases “integrity” (within-network functional connectivity (FC))
  • decreases between-network FC (“segregation”)
  • increases the repertoire of (less comprehensive) brain connectivity profiles
  • results in a globally hyperconnected brain state
  • results in freer transitions between brain states
  • reduces the principal sensory-association cortex gradient
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