Disintegration of Default Mode: Functional MRI Insights Into N,N-Dimethyltryptamine (DMT), Consciousness, and Subcortical Connectivity.

N,N-Dimethyltryptamine (DMT), a potent endogenous psychedelic, evokes rapid and immersive shifts in consciousness that challenge conventional neurocognitive models. Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG)-fMRI studies suggest that these altered states are not chaotic but patterned, marked by a disruption of the default mode network (DMN), an increase in global integration, and heightened subcortical activity. Under the influence of DMT, the brain becomes less modular and more fluid, reorganizing itself into a hyperconnected state. Activity increases in the thalamus, amygdala, and hippocampus, regions involved in memory, emotion, and sensory salience. Meanwhile, the cortical regions typically responsible for self-referential processing lose their organizing control. This temporary collapse of hierarchical brain structure is associated with vivid imagery, emotional release, and a loosening of the boundaries that define the self. Rather than simply distorting perception, DMT appears to reveal the brain's capacity to restructure consciousness itself. These findings suggest that consciousness may not be a fixed entity housed within a singular network but a flexible process shaped by context, neurochemistry, and meaning.