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How damage to hippocampus hinders memory but not acquisition of knowledge

August 12, 2011 - Washington

In a case study, clinical neuropsychologists have been able to determine how damage to hippocampus very early in life hinders recollection of specific events but spares acquisition of general knowledge.

Memory is not a single process but is made up of several sub-processes relying on different areas of the brain. Episodic memory, the ability to remember specific events such as what you did yesterday, is known to be vulnerable to brain damage involving the hippocampus.

Dr. Claire Bindschaedler and Dr. Claire Peter-Favre from the Neuropsychology Unit of Lausanne's University Hospital in Switzerland, together with their colleagues Prof. Philippe Maeder, Dr. Therese Hirsbrunner and Prof. Stephanie Clarke, investigated the case of a patient known as VJ.

Repeated neuropsychological testing showed that VJ could not remember being read a story or shown a picture half an hour earlier, or at least remembers little of it.

At the same time however, VJ does do well on tests of general knowledge, also called semantic memory.

In fact, when tested regularly over his childhood and teenage years, VJ was found to develop at the same rate as other children in areas of general knowledge and general intelligence.

Analysing MRI scans of VJ's brain, Maeder found very severe atrophy (wasting away of brain tissue) in the hippocampi, while the adjacent area of the brain, known as the perirhinal cortex, was relatively spared from damage.

This latter area is hypothesised to be important for the acquisition of semantic memory.

These findings lend support to the idea that episodic memory (but not semantic memory) depends on the hippocampus.

The study has been published in the September 2011 issue of Elsevier's Cortex.


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