Our understanding of how memory breaks down
after brain damage may have to be revised according to new research carried
out by Morgan Barense and colleagues at the MRC Cognition and Brain Sciences
Unit in Cambridge, and recently published in the Journal
of Neuroscience.
This research may have implications for the early diagnosis
of brain damage
and our approach to rehabilitation. Until now, scientists believed that structures in the brain’s
medial temporal lobe (MTL) made up a single functional system, or module,
that supports learning of new memories and was independent of other cognitive
functions, such as language and perception. The MRC scientists have now
shown, however, that there is a division of labour within the MTL - not
all parts support the same type of memory - and also that these parts
may play a role in perception as well as memory.
The research was carried out in individuals who had suffered damage
to different parts of the MTL, the perirhinal cortex and/or the hippocampus.
People with damage to the perirhinal cortex had extreme difficulty in
memorising objects when they had several features in common (e.g., comparing
pictures of a zebra and a tiger or comparing barcodes) but showed normal
learning when the objects looked distinct. As the amount of information
to be remembered was identical for similar and dissimilar objects, this
result implies an underlying difficulty with perception of objects. In
contrast, amnesic individuals with damage limited to another part of
the MTL, the hippocampus, performed normally on these tests. This suggests
that the hippocampus, long thought to be the neural basis for memory,
is not critical for memory for objects, but may, as other experiments
have shown, play an important role in spatial memory and perception,
for example in remembering a route home from work. The type of material
a memory-impaired individual is asked to learn, therefore, influences
the likely success of their learning.
MRC lead scientist, Morgan Barense said,
“ As damage to the medial
temporal lobe (MTL) is associated with many types of disease, including
Alzheimer’s disease, this research shows that memory may not be
as globally affected as previously believed. This has implications for
the development of more accurate tests for early diagnosis and differentiation
of dementia, as well as for the way we think about rehabilitation of
memory loss.”
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item was first released by the Medical Research Council (MRC) on 2nd
November 2005. For further information, please visit
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Pub: 4 November 2005
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