Chronic cannabis users, even after a period of abstinence, are more prone to false memories—mistaking events that never occurred for real ones. Using functional magnetic resonance imaging, the study found that abstinent cannabis users showed reduced brain activity in areas critical for memory processing, including the lateral and medial temporal lobe, as well as in parietal and frontal regions involved in attention and monitoring. Cannabis consumption was inversely correlated with medial temporal lobe activity, indicating a specific detriment to episodic memory. These results suggest long-lasting impairments in memory and cognitive control mechanisms that support reality monitoring.
Psychosis in Parkinson disease (PDP) includes illusions, hallucinations, and delusions that can appear even early in the disease. While once thought to be solely a side effect of dopaminergic drugs, evidence now shows PDP results from the disease's own brain changes combined with medication. Dysfunction in attentional control, sensory processing, limbic structures, the default mode network, and thalamocortical connections leads to incorrect categorization of stimuli and false percepts. This review covers recent clinical, neuroimaging, and neurochemical findings that may help identify psychotic phenomena early and guide new treatments.