The
hippocampus is a brain structure which lies under the medial
temporal lobe, one on each side of the brain. It is sometimes
grouped with other nearby structures including the dentate
gyrus and called the "hippocampal formation." The hippocampus
is critical for the formation of new autobiographical and
fact memories. It may function as a memory "gateway" through
which new memories must pass before entering permanent storage
in the brain. Hippocampal damage can result in anterograde
amnesia: loss of ability to form new memories, although
older memories may be safe. Thus, someone who sustains an
injury to the hippocampus may have good memory of his childhood
and the years before the injury, but relatively little memory
for anything that happened since.
Some memories, such as the memory for new
skills or habits, can sometimes be formed even without the
hippocampus. A current research area is to determine exactly
what kinds of learning and memory can survive hippocampal
damage, and how these kinds of learning can be used to guide
rehabilitation.
The hippocampus is especially sensitive to global reductions
in oxygen level in the body. Thus, periods of oxygen deprivation
(hypoxia)
which are not fatal may nonetheless result in particular damage
to the hippocampus. This could occur during a heart attack,
respiratory failure, sleep apnea, carbon monoxide poisoning,
near-drowning, etc. The hippocampus is also a common focus
site in epilepsy, and can be damaged through chronic seizures.
It is also sometimes damaged in diseases such as herpes encephalitis,
and is one of the first brain areas to show damage in Alzheimer's
disease.
Further Reading:
L. Squire & E. Kandel (2000) Memory:
From Mind to Molecules. New York: Scientific American
Library.
Article : "REMEMBERING
TO SMELL THE ROSES"
Article : "MEMORIES
LOST AND FOUND"
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain
Artwork copyright © 2000 Ann L. Myers
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