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. 2023 Nov 6;22(4):636–735. doi: 10.2174/1570159X22666231027111147

Fig. (6).

Fig. (6)

Effects of classic psychedelics on the brain. Psilocybin decouples functional connectivity between the ventral medial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC) in the Default Mode Network (DMN). Acute decreases in cerebral blood flow and bold signaling are observed in the thalamus and in the anterior and posterior cingulate cortices following psilocybin ingestion [378]. The intensity of the subjective effects of psilocybin is predicted by the magnitude of decreased activity within the anterior cingulate cortex (ACC) and medial prefrontal cortex (mPFC) [378]. Psilocybin also decreases amygdala reactivity to negative and neutral stimuli [592]. LSD reduces associative connectivity (i.e., medial and lateral prefrontal cortex, cingulum, insula, and temporoparietal junction) and simultaneously increases sensory-somatomotor (i.e., occipital cortex, superior temporal gyrus, postcentral gyrus, and precuneus) brain-wide and thalamic connectivity [578]. LSD, similar to psilocybin, acutely decouples functional connectivity between the ventral medial prefrontal cortex and posterior cingulate cortex in the DMN. Moreover, LSD decreases connectivity between the parahippocampus and retrosplenial cortex, which has been correlated with clinically measured ratings of “ego-dissolution” and “altered meaning” [580]. Ayahuasca ingestion significantly decreases activity through most parts of the DMN, including the posterior cingulate cortex (PCC)/precuneus and the medial prefrontal cortex (mPFC). Additionally, functional connectivity within the PCC/precuneus is significantly decreased [577, 582].