Lysergic acid diethylamide (LSD) increases global functional connectivity in the brain, and this neural change correlates with the experience of ego dissolution—a temporary loss of the sense of self. The more the brain's networks became globally interconnected under LSD, the more participants reported a diminished or dissolved sense of self. This suggests that the subjective feeling of ego dissolution is linked to a breakdown of the normal modular organization of brain connectivity.
A multimodal neuroimaging model incorporating serotonin receptor maps across the whole brain explains the non-linear functional effects of LSD. The model shows that LSD's influence on brain activity is not uniform but depends on the density of serotonin receptors in different regions, leading to complex, non-linear changes in functional connectivity and network organization. This approach integrates receptor distribution data with brain imaging to predict how LSD alters brain function, offering a mechanistic account of its psychoactive effects.
Psychedelics are consciousness-altering compounds that act on serotonin receptors in the brain. First called 'psychedelic' in 1956, they are also known as hallucinogens, entheogens, or empathogens, reflecting their diverse subjective effects. Hundreds of such compounds exist with a range of behavioral and neurobiological impacts. Recent evidence that psychedelics can effectively treat mental illnesses has renewed scientific interest in their neural mechanisms. This Primer offers a concise overview of current scientific data for those entering the field.