[Neuroimaging correlates of classical psychedelics effects: A systematic review].

Background: Current scientific literature supports classical psychedelic efficacy in many psychiatric disorders. However, less attention has been given to the neurological effects of these substances. The aim of this medical thesis was to conduct a systematic review examining the neuroimaging correlates of the effects of psychedelics.

Method: We performed an electronic research through Medline and Science Direct databases. A comprehensive search yielded 460 articles published up to May 2022. After a cautious screening process, we selected 49 scientific papers for further analysis.

Results: Major findings included reduced functional network integration, increased between-network functional connectivity, and expansion of functional connectivity patterns repertoire under psychedelics. Thalamic gating and emotional processing were also impaired. These results positively correlated with symptom improvement in pathological populations.

Conclusion: To this day, our knowledge concerning psychedelic effects remains partial. Several neurocognitive theories have been developed in recent years to model psychedelic phenomenology, but no unifying theory has emerged. Studies involving larger populations investigating various psychiatric disorders, including several neuroimaging modalities and considering medium- and long-term effects, would be necessary to deepen current knowledge.