Developmental psychology.pdf

234 Learning ani Information Processing
Figure 9.1
Problem of Amnesia. Victims of
amnesia sometimes find themselves
in a strange city without any form of
identification. The person, for
example, may be sitting on a park
bench with no knowledge of himself
except the vague feeling that his
name may be Paul. Newspaper
stories and photographs often help
the family to contact the individual
and thereby recover the past.
for he could not remember having met them previously. H. M. was in many respects
a social bore, for after the surgery he did not recall what he had just said to anyone.
The stories he remembered of course were those from childhood, and he told them too
often (Milner, Corkin, & Teuber, 1968).
This case and others show that the hippocampus is significantly involved in
memory, but its exact role is still uncertain. The function may pertain to storing new
memories— that is, retaining them initially—or it may lie in retrieval, in which case
the memory is stored in some fashion but the individual cannot resurrect it. Or both
difficulties may be involved. At this point the role of various brain structures in amnesia
is poorly understood and the subject is of considerable debate (Hirst, 1983).
Another common form of amnesia, retrograde amnesia, involves a loss of
memory for old experiences, especially those preceding a traumatic event. This type
of amnesia is often the result of some blow to the head, as in an accident, after which
the afflicted individual is unable to recall the previous details, such as going to work,
reaching the construction site, mounting the framework, reaching for a certain tool,
and so forth. A similar form of forgetting may occur more briefly and in a smaller
amount among people who have received electroconvulsive therapy. In both cases there
is a gradual recovery of memory for events closer and closer to the traumatic episode,
and those immediately preceding it are the last to be remembered, if they are recovered
at all.
Overall, the behavioral manifestations of amnesia have been carefully documented
in several cases, but it has been difficult to demonstrate that damage to a particular
brain structure is the basis of amnesia. The hippocampus appears implicated
but, as yet, in some unspecified manner (Hirst, 1983; Figure 9.1).
Function of the Trace
So much for the physiological basis of memory, whatever its nature. RNA, synapses,
and hippocampal areas all may be uniquely involved. But apart from memory's underlying
stucture, one might ask an equally compelling question: How does the memory
trace work? The research and speculation here have significance for much of the
rest of this chapter.