Tuesday, 19 December 2006

Investigating the 'dreamy state'

Patients with temporal lobe epilepsy sometimes experience unusual hallucinations and strange sensations when they have a seizure. Back in the nineteenth century, the legendary English neurologist John Hughlings Jackson called these experiences ‘dreamy states’. Now a team of French researchers, led by Jean-Pierre Vignal, have re-visited these strange phenomena.

One hundred and eighty epileptic patients were having parts of their brains stimulated and recorded from, to try to establish the source of their seizures. During these tests, Vignal’s team found 17 of the patients reported a total of 55 dreamy state experiences, some were a result of seizures, others were caused by the stimulation.

A frequent experience reported by the dreamy state patients was deja vecu (like déjà vu but involving all the senses). As one patient explained:
It’s like in my seizures, I’m reliving something…but I can see you clearly…It’s as if what is happening now has already happened to me, it’s like an old memory that I am in the middle of living out”.

However, at other times, the sensation was more like a visual hallucination:

I see myself playing the drums, with people from my family listening to me”, another patient said.

Such hallucinations always involved personal memories from either the recent or distant past, but never featured public or historical events. This fits with the fact the dreamy states were provoked by a seizure in, or stimulation of, the mesial temporal lobe, the seat of our autobiographical memories.

Vignal, J-P., Maillard, L., McGonigal, A. & Chauvel, P. (2007). The dreamy state: hallucinations of autobiographic memory evoked by temporal lobe stimulations and seizures. Brain, 130, 88-99.

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

No comments:

Post a Comment

Note: only a member of this blog may post a comment.