From Christian Holscher, School of Biomedical Sciences, University of Ulster
Your article on déjà vu prompted me to experience an episode of it myself (28 March, p 28).
A few years ago, I worked at the University of Oxford monitoring the neuron response of primates that performed visual memory tasks. We found that many neurons responded most when a new image was shown. However, there was also a population of neurons that responded most to familiar images. This was not to specific images, as one would expect, but rather to all familiar images (Neural Plasticity, vol 9, p 41, European Journal of Neuroscience, vol 18, p 2037).
The brain area we were looking at was the perirhinal cortex in the temporal lobe, next to the perirhinal cortex mentioned in the article, which works hand in hand with the visual long-term memory system. We concluded that there must be an independent system that associates visual information with a “familiarity” response if the conditions are right.
If this system exists, then it could go awry. When it fails to work, we just call it amnesia. If it works all the time, symptoms of constant déjà vu can appear.
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Coleraine, Londonderry, UK
