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Chapter 8
The second broad category of memory,
procedural
memory,
can be defi ned as the memory of how to do things.
In other words, it is the memory for skilled behaviors inde-
pendent of any conscious understanding, as for example,
riding a bicycle. Individuals can suffer severe defi cits in declar-
ative memory but have intact procedural memory. One case
study describes a pianist who learned a new piece to accom-
pany a singer at a concert but had no recollection the follow-
ing morning of having performed the composition. He could
remember how to play the music but could not remember hav-
ing done so. The category of procedural memory also includes
learned emotional responses, such as fear of spiders, and the
classic example of Pavlov’s dog, which learned to salivate at
the sound of a bell after the dog had previously associated the
bell with food. The primary areas of the brain involved in pro-
cedural memory are regions of sensorimotor cortex, the basal
nuclei, and the cerebellum.
Another way to classify memory is in terms of duration—
does it last for a long or only a short time?
Working mem-
ory,
also known as
short-term memory,
registers and retains
incoming information for a short time—a matter of seconds to
minutes—after its input. In other words, it is the memory that
we use when we keep information consciously “in mind.” For
example, you might look up a number in the phone book and
remember it only long enough to walk across the room and dial
it. Working memory makes possible a temporary impression of
one’s present environment in a readily accessible form and is an
essential ingredient of many forms of higher mental activity.
Short-term memories may be converted into
long-term mem-
ories,
which may be stored for days to years and recalled at a
later time. The process by which short-term memories become
long-term memories is called
consolidation.
Focusing attention is essential for many memory-based
skills. The longer the span of attention in working memory, the
better the chess player, the greater the ability to reason, and the
better a student is at understanding complicated sentences and
drawing inferences from texts. In fact, there is a strong correla-
tion between working memory and standard measures of intel-
ligence. Conversely, the specifi c memory defi cit that occurs in
the early stages of
Alzheimer’s disease,
a condition marked by
dementia and serious memory losses, may be in this attention-
focusing component of working memory.
The Neural Basis of Learning and Memory
The neural mechanism and parts of the brain involved vary
for different types of memory. Short-term encoding and long-
term memory storage occur in different brain areas for both
declarative and procedural memories (
Figure 8–14
).
But what is happening during memory formation on a
cellular level? Conditions such as coma, deep anesthesia, elec-
troconvulsive shock, and insuffi cient blood supply to the brain,
all of which interfere with the electrical activity of the brain,
also interfere with working memory. Thus, it is assumed that
working memory requires ongoing graded or action poten-
tials. Working memory is interrupted when a person becomes
unconscious from a blow on the head, and memories are abol-
ished for all that happened for a variable period of time before
the blow, a condition called
retrograde amnesia
.
(
Amnesia
is
defi
ned as the loss of memory.) Working memory is also sus-
ceptible to external interference, such as an attempt to learn
confl icting information. On the other hand, long-term mem-
ory can survive deep anesthesia, trauma, or electroconvulsive
shock, all of which disrupt the normal patterns of neural con-
duction in the brain. Thus, working memory requires electri-
cal activity in the neurons.
Another type of amnesia is referred to as
anterograde
amnesia
.
It results from damage to the limbic system and
associated structures, including the hippocampus, thalamus,
and hypothalamus. Patients with this condition lose their abil-
ity to consolidate short-term declarative memories into long-
term memories. While they can remember stored information
and events that occurred before their brain injury, they can
only retain anything that happens from that point forward in
time as long as it exists in working memory. One particularly
striking case report describes a woman whose husband died
of a heart attack shortly after she suffered a stroke that perma-
nently damaged her limbic system. At regular intervals dur-
ing her recovery and thereafter, she would cheerfully inquire
whether her husband would be coming for a visit, only to
repeatedly re-experience the emotional shock and grief when
told of his fate.
The problem of exactly how memories are stored in the
brain is still unsolved, but some of the pieces of the puzzle
are falling into place. One model for memory is
long-term
potentiation (LTP),
in which certain synapses undergo a
long-lasting increase in their effectiveness when they are heav-
ily used. Review Figure 6–36, which details how this occurs
at glutamatergic synapses. An analogous process,
long-term
depression (LTD),
decreases
the effectiveness of synaptic con-
tacts between neurons. The mechanism of this suppression of
activity appears to be mainly via changes in the channels in the
postsynaptic membrane.
Declarative memory
Short-term
Hippocampus and other
temporal lobe structures
Long-term
Many areas of
association cortex
Procedural memory
Short-term
Widely distributed
Long-term
Basal nuclei
Cerebellum
Premotor cortex
Figure 8–14
Brain areas involved in encoding and storage of declarative and
procedural memories.
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