Disturbance of the sense of self may be a core marker of schizophrenia. In patients with first-episode schizophrenia-spectrum disorders compared with healthy controls, self-agency experience was associated with reduced cortical activation in the medial frontal gyrus and posterior cingulate gyrus. The ability to judge whether an action is one's own or another's depends on anti-correlated switching between the default mode and central-executive networks, a mechanism substantially impaired in the patient group during the task.
Delta-9-tetrahydrocannabinol, the active compound in cannabis, temporarily alters how brain regions communicate with each other. In 19 occasional cannabis users who underwent two resting-state fMRI scans—one shortly after smoking a cannabis cigarette and one after at least a week without cannabis—a transient connectivity state appeared only during intoxication. This state showed high connectivity within and between auditory and somato-motor cortices, along with anti-correlation with subcortical structures and the cerebellum. Subjective perceptual changes and THC plasma levels were linked to this state, suggesting a neural biomarker of cannabis intoxication.
The ability to judge whether an action is one's own or another's depends on dynamic switching between two large-scale brain networks: the default mode network (DMN) and the central-executive network (CEN), which normally work in opposition. In people with first-episode schizophrenia spectrum disorders, this antagonistic switching mechanism is substantially impaired, and the degree of impairment correlates with poorer performance on self-agency judgment tasks. The findings suggest that a core pathology in schizophrenia may lie in the higher-order regulatory mechanisms that coordinate these networks.