National Institute of Mental Health

                                        National Institutes of Health
 
 

Fact Memory Spared Despite Hippocampal Damage

Contacts: Jules Asher
NIMH
301-443-4536
Francis Tuke
Inst. of Child Health, London
44-171-829-8671

EMBARGOED UNTIL: 4:00 PM, July 17, l997
 
 

Research by scientists at the Institute of Child Health in London, published
in the July 18th issue of Science, provides new insight into how memory
works. Even if the hippocampus - the part of the brain long thought of as
being critical for memory - is damaged, the underlying regions can still
carry out some important memory functions, reports the research team,
which includes senior author Mortimer Mishkin, Ph.D., National Institute of
Mental Health, NIH, Bethesda, MD.

The findings may hold new hope for children with memory problems and
have implications for healthcare professionals and teachers involved in the
assessment and education of children with special needs.

The researchers studied three young people who had suffered oxygen
deprivation and consequent brain injury early in life. Brain scans using
magnetic resonance imaging techniques revealed damage to the
hippocampus, an especially vulnerable structure in the middle of the brain.
Although they suffered from amnesia and were unable to recall events
from their everyday life with any reliability, the children all attended
mainstream schools and were able to gain average grades in most of their
classwork, particularly in speech and language, reading and writing, and
factual knowledge.

For example, they might know the name of the capital of Italy, but
remember nothing about their vacation there last year. Similarly, they
cannot reliably remember messages or appointments or find their way
around even familiar surroundings. These types of deficits did not become
obvious until the age of five or six, but now severely restrict their
independence.

One influential school of thought holds that if the memory system is
damaged, both 'episodic' memory (memory for events) and 'semantic'
memory (memory for facts) would be impaired equally. The new study
suggests that even though these two different types of memory normally
work together and interdependently, if only the hippocampus is damaged,
a child can develop fact memory surprisingly well through the functioning
of the underlying cortices.

"These new case studies offer a particularly impressive example (of
preserved fact memory) that can be attributed to selective focal
hippocampal damage early in life," observes Boston University
neurobiologist and NIMH grantee Howard Eichenbaum, Ph.D., in an
accompanying "perspective" in the same issue of Science.

Previously, there had been no report of this kind of amnesia after very
early brain damage, and it was thought that early injury to the
hippocampus might well stunt intellectual development -- with the result
being not just amnesia, but mental retardation.

"As a result of this study, we need to rethink how children with special
needs are assessed and diagnosed," said Dr. Faraneh Vargha-Khadem,
neuropsychologist at the Institute of Child Health, who led the research.
"If children with this type of amnesia can be diagnosed early, then
appropriate remediation can be given early on, perhaps even before school
entry. If we can do this, we may be able to give these children the
opportunity to live a more independent life."

Since their discovery of the syndrome, Dr Vargha-Khadem and colleagues
have so far identified some 15 children suffering from such amnesia due to
oxygen deprivation, which can occur during difficult or premature birth or
heart surgery. The research team plans to screen groups of young children
who may be at risk in hopes of providing early intervention.

The National Institute of Mental Health is a component of the NIH, an
agency of the U.S. Public Health Service, part of the U.S. Department of
Health and Human Services.

                                        Posted: July 17, 1997