Meditation is linked to reduced activity in the default mode network, a brain system tied to self-focused thought and mind wandering, even when compared to an active cognitive task rather than just rest. In a larger group than prior studies, meditators showed less default mode network activation during meditation than non-meditators performing a control task. Key regions involved were the posterior cingulate/precuneus and anterior cingulate cortex. These findings suggest that suppression of default mode processing is a central neural process in long-term meditation, extending beyond what is seen during other effortful tasks.
A single modest dose of oral THC (15 mg dronabinol) worsened verbal learning and attention in people with schizophrenia and co-occurring cannabis use disorder, without exacerbating psychotic symptoms several hours after administration. Smoked low-dose THC cigarettes did not produce these cognitive effects. Higher blood THC levels were linked to increased negative symptoms. Drug liking was greater with THC than placebo. The findings suggest that oral THC may impair cognition in this population even at modest doses, while not acutely worsening psychosis.