What causes déjà vu?
- Published4 Jun 2014
- Reviewed4 Jun 2014
It is difficult to study déjà vu — the odd feeling you get when you sense you’ve already experienced something that you know you are doing for the first time — in the laboratory. This is mainly because the phenomenon is rare and difficult to reproduce. However, there are similarities between déjà vu and the more common experience of seeing a person who seems vaguely familiar to you, but whose name, how you know them, and where you previously met escape you.
Unlike déjà vu, scientists are able to test feelings of familiarity in the laboratory. One way they do this is by asking study participants to scan and quickly assess the familiarity of faces or places they have seen before and those that they are seeing for the first time. Such studies have helped researchers come to understand that familiarity and recollection are two different forms of memory that work together during recognition. While people experience the sense of familiarity rapidly, recollection, which requires the recovery of associations prompted by a critical cue, takes longer. For instance, if you begin a casual conversation with that person you know you recognize but cannot quite place, you may start to uncover details that trigger memories revealing the person’s name and how you know them.
Functional MRI (fMRI) studies of people asked to judge the familiarity of faces and buildings have revealed that when people distinguish familiar from novel faces, changes in activity occur in an area of the temporal lobe called the perirhinal cortex. By contrast, an adjacent area called parahippocampal cortex is shows activity changes when people distinguish familiar buildings from those they are seeing for the first time.
Thus, déjà vu for a face may be the result of messages sent from the perirhinal cortex whereas déjà vu for a place may stem from messages relayed from the parahippocampal cortex. Notably, both of these regions send their information to the hippocampus, which supports recollection. So, the full experience of recollection may reflect a combining of converging signals from both perirhinal and parahippocampal areas to the hippocampus.
Eichenbaum H, Yonelinas AR, Ranganath C. The medial temporal lobe and recognition memory. Annual Review of Neuroscience. 30:123-152 (2007).
Martin CB, McLean DA, O’Neil EB, Kohler S. Distinct familiarity-based response patterns for faces and buildings in perirhinal and parahippocampal cortex. The Journal of Neuroscience. 33:10915–10923 (2013).
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