Déjà vu is experienced by 73% of healthy Italian adults, with frequency declining as age increases. The Italian version of the Inventory Déjà Vu Experiences Assessment (I-IDEA) reliably detects and characterizes the phenomenon. In a sample of 542 healthy volunteers aged 18–70, déjà vu was inversely related to age, derealisation, jamais vu, precognitive dreams, depersonalization, paranormal activity, remembering dreams, travel frequency, and daydreams.
In people with psychogenic non-epileptic seizures (PNES), a type of dissociative event, brain activity patterns shift markedly during the events compared to resting periods. EEG microstate analysis of 22 PNES patients and 24 healthy controls showed that microstate C, linked to the default mode network, was more prominent at rest in patients than in controls, but its duration, coverage, and global field power all decreased significantly during PNES events. This suggests a major change in default mode network dynamics during dissociative events, pointing to a mix of pathological and adaptive brain processes underlying PNES.