Physiological Basis of Memory

Theories of learning and memory have been of great concern to philosophers
and psychologists for a long time. They have formed a major part of
the history of psychology. Each of the theories has been ascendant for a
time, but the nature of theory building requires new conceptions to compensate
for perceived weaknesses in currently accepted theories and models.
Associationism was the principal theory of memory of stimulus-response
psychology, which was dominant in the United States until the mid-1950’s.
Cognitive psychology evolved from Gestalt psychology, from Jean Piaget’s
work on developmental psychology, and from information-processing theory
associated with the computer, and was extremely important during the
1970’s and 1980’s. Neuropsychology developed concurrently with advanced
technology that permits microanalysis of brain functioning. It has resulted
in an explosion of knowledge about how the brain and its systems operate.
Formation of memory seems to involve two individual events. Short-term
memory develops first. Repeated rehearsal transfers this form of memory
into long-term storage. At one time, it was believed both these forms of
memory involved similar events in the brain. However, experimental models
have shown such a theory to be incorrect. Two experimental approaches
have addressed this issue: the separation of memory formation involving
“accidental” or intentional interference with brain function, and development
of an animal model for the study of memory.
Electroshock treatment of depression in humans has been shown to interfere
with short-term memory formation. However, these persons are still perfectly able to recall the memory of earlier events stored within long-term
memory. Accidental damage to temporal lobes of the brain does not appear
to interfere with short-term memory, but may inhibit the ability to recall
events from the past.
The experimental use of an animal model in the study of memory formation
was developed by Eric Kandel at Columbia University. Kandel has utilized
the sea slug Aplysia in his study of memory. The advantage of such a
model is its simplicity—instead of approximately one trillion neurons which
make up the nervous system of humans, Aplysia contains a “mere” twenty
thousand.

Using a variety of stimuli on the animal, and observing its response,
Kandel has shown that the physiological basis for short-termmemory differs
from that of long-term. Specifically, short-termmemory involves stimulus to
only a small number of individual neurons. Long-term memory involves de
novo (new) protein synthesis in the affected cells, and formation of extensive
neural circuits. Kandel was awarded the Nobel Prize in Physiology or
Medicine in 2000 for this work.