Bergouignan, L. 1, 2 , Nyberg, L. 3 & Ehrsson, H. 1
1 Department of Neuroscience, Karolinska institutet
2 BCBL
3 Umea university
We generally encode life-experiences into memory from a first-person in-body representation. But how dependent is the hippocampal long term memory system to this in-body representation?
While participants were involved in a social interaction, an out-of-body illusion was elicited, in which the sense of bodily self was displaced from the real body to the other end of the testing room. This condition was compared with a well-matched in-body illusion condition, in which the sense of bodily self was colocalized with the real body. In separate recall sessions, performed ?1 wk later, we assessed the participants? episodic memory of these events. The results revealed an episodic recollection deficit for events encoded out-of-body compared with in-body. Functional magnetic resonance imaging indicated that this impairment was specifically associated with activity disturbance in the posterior hippocampus.
These findings suggest that the in-body encoding is necessary for the formation of the long term memory of an event. The results thus provide the first step in the explanation for the link between the impaired episodic memory and dissociative symptoms (where a person feels detached from their own body) that occur in clinical conditions such as post-traumatic stress disorder and schizophrenia.