DMT: Dimethyltryptamine

DMT is a psychedelic drug that alters consciousness, making it useful when studying areas of the brain associated with consciousness. In a study done to analyze DMT’s effects on the brain, it was found that DMT enhances global functional connectivity and decreases hierarchical organization and integration of resting-state networks. DMT also greatly affected areas with highest concentrations of serotonin 2A receptors, which corresponded with regions related to higher cognition, such as language and semantics. The results suggest that DMT impacts brain organization and therefore the quality of the conscious experience. 

LSD: Lysergic acid diethylamide

LSD is another psychedelic drug that is being increasingly studied for treatment of psychiatric disorders because of its effects on serotonin. When examining the whole brain effects of LSD, one study reported greater interregional connectivity and increased self-inhibition in all areas except the occipital and subcortical regions. Therefore, LSD is shown to impact the excitation/inhibition balance, although the mechanism of action is not well understood. The excitation/inhibition balance may play a role in psychedelic-induced hallucinations and synesthesia, which may have key implications in manifestations of clinical psychosis. 

Magic Mushrooms: Psilocybin

A psychedelic drug that alters time perception, reality-testing, and cognition related to the self, is psilocybin. Because ego-dissolution is a highlighted as a result of the drug, psilocybin has been used to assess this phenomenon in the brain. It was found that disintegration of the salience network and decreased communication within hemispheres of the brain was correlated with ego-disintegration. Further, medial temporal lobe decoupling and decreased salience network integration are also suggested to influence perception and maintenance of the ego. These results may have implications in studying ego disturbances in other disorders, such as schizophrenia.

Sources: 

Bedford, et al., (2023). The effect of lysergic acid diethylamide (LSD) on whole-brain functional and effective connectivity. Neuropsychopharmacology

 Lebedev, et al., (2015). Finding the self by losing the self: Neural correlates of ego‐dissolution under psilocybin. Human Brain Mapping

Timmermann, et al. (2023). Human brain effects of DMT assessed via EEG-fMRI. PNAS Proceedings of the National Academy of Sciences of the United States of America.