Memory, like intelligence,
does not have a distinct definition. However, most scientists agree memory is
the storing and recalling of information, characterized by the systems, representations
and processes in living organisms that take part in this ability. Memory can be
the knowledge of riding a bike or recognizing the smell of vanilla muffins.
While how memories
are formed is not yet fully understood, it is theorized that the architecture
of the brain is constantly being modified as new information is stored. The number
and efficiency of synapses (communication area between the two neurons) increase
and new neural pathways are formed.
There are many
categories that memory can be divided into, three of which being short-term memory
(STM), intermediate-term memory (ITM) and long-term memory (LTM). STM is like
the random access memory (or RAM) on your computer. RAM allows you to read this
section of The Brain Explorer without it disappearing because it is temporarily
stored on your computer. Moreover, as I was writing this section, each letter
I typed remained on the screen because of RAM. However, if I were to turn off
the computer before saving, everything I had just typed would be erased. Like
your computer, information in our brain stored as STM will disappear if it is
not stored permanently (LTM). Generally, STM lasts from a few seconds to an hour.
In addition, the amount of information stored in STM is limited and dependent
on attention.
Similar to STM
is ITM. However, ITM lasts somewhat beyond STM. For example, suppose you ride
your bike to school every morning and place your bike in a different bike rack
each day. Generally, by the end of the day, you usually remember which bike rack
to find your bike. However, it may be unlikely that you are able to recall where
you placed your yesterday or a week ago.
On the contrary,
LTM can be held for as long as a lifetime. For information to be stored in LTM,
it must first be stored as STM. Eventually the STM becomes permanently stored
in the brain. However, how this transition from STM to LTM works is not well
known.
Processes related
to ITM and LTM can be subdivided into the four "R's":
Recollection
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The
reconstruction of events or facts on the basis of partial cues.
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Recall
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The
active and unaided remembering of something from the past.
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Recognition
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The
ability to correctly identify previously encountered stimuli as familiar
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Relearning
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Learning
material for the second time in which it usually becomes easier.
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Memory can also
be categorized as declarative or non-declarative memory. Declarative memory is
the conscious recall of information such as facts or events whereas non-declarative
memory is remembering how to perform a procedure such as clapping or walking.
In other words, declarative memory can be viewed as remembering "what"
while non-declarative memory is remembering "how". Declarative memory
has been found to exist in and around the temporal lobes. Moreover, our capacity
for declarative memory remains relatively constant throughout life except during
old age where brain plasticity (the ability for the brain to adapt and change)
decreases. Non-declarative memory is stored in multiple areas of the brain and
is most operative during early childhood.
