Of all the important and fascinating things about the brain, memory
seems to be at the top of the list. People always seem to think of
memory when they talk about learning or “being smart.”

This certainly applies to college students. In fact, I fear that many
of them rely almost totally on memorization in preparing for exams.
For example, they write chemical reactions on different colored cards
because they can remember the color easily. Then, for the test, they
remember that this reaction is a green one, and that reaction is a red
one, when the color of the card really has nothing to do with
chemistry. It is just a trick.

But I don’t want to downplay the importance of memory. Certainly,
memory is an essential tool for learning. And, as we learn to our
sorrow when Alzheimer’s disease strikes, memory also lies at the heart
of our identity and our ability to function at an even minimal level.
Any “smart” action or thought also has memories embedded and
supporting it!

So how does it work? What is memory? Where is memory? How long does
it last? How can I keep my memory?

Let’s begin with the where question, as brain surgeons and scientists
did nearly a century ago. Then, and for a long time to follow, it
seemed that memory must be located in a specific part of the brain.
Probably it was just like language, with its well known Wernike’s and
Broca’s areas. But as the search continued, it became a little bit
desperate. No one could find that “memory center.” Memory was nowhere
and everywhere, it seemed.

Now this conclusion seems to make sense. Memories are networks of
neurons that trigger firing in each other. When one neuron fires,
others also fire because they are part of the network. And even if
some neurons don’t fire immediately, they and their more distant
associated partner networks may fire later, if the stimulus is
repeated. Thus, we recall parts of things immediately, but assemble
the larger memory bit by bit.

The thing that makes the memory so elusive is that the neurons of the
various parts of the network may be found anywhere in the brain. If
the memory is something we saw, the networks will contain neurons in
the visual cortex. If it is of a person talking to us face to face,
the network will include neurons in both the visual and the auditory
cortex. If the memory is of a beautiful person holding our hand, the
neurons of the network will include the visual cortex, the
somatosensory cortex, and the emotion centers of the brain; perhaps
the nucleus accumbens which is rich in dopamine receptors!

Memories are spread out. Maybe we shouldn’t even think of finding
them!

If the where question is a dead-end, maybe we can pin down memory in a
different way. We often hear that there are different kinds of memory.
For example, how about “semantic” memory (language labels for objects,
actions, etc), episodic memory (experiences and the time sequence of
events,) and procedural memory (remembering how to do things.) Or,
maybe there are different lengths. What about short term and long
term memory. Or, to add to the confusion, what about the kind of
memory used to solve problems, “working memory”?

At first, these labels seem to make sense. Almost every book on memory
uses them. But we have to admit that they can generate a lot of
confusion too. I have trouble with this all the time. My students may
be puzzled and claim “episodic memories are full of declarative
memories,” or “declarative memory has no meaning unless we know the
episodic memory that goes with it!” They also immediately notice that
the labels “short term” and “long term” imply that there is nothing in
between. And they don’t believe it. Some things we remember for
seconds, others for minutes, hours, days…… So, how long is long? How
short is short?

Inquiring students want to know! “How short is short, Dr. Zull?”

The answer may sound quite familiar by now. Just as there seem to be
memories at all possible locations in the brain, there also seem to be
memories of all lengths. Short term and long term may be useful when
used in a technical way by cognitive scientists, but don’t take them
too literally.

So we may not have traveled as far as we think in cognitive
neuroscience. It is still easy to forget the distributed nature of
memory; memory as a continuum of time, location, and type. A three
dimensional ghost! And the only thing that rescues us is our notion of
the integrated brain. Many parts of the brain are connected with each
other and influence each other. And the dynamic process of synapse
gain and loss means that networks may function for different lengths
of time.

We must acknowledge this distributed and dynamic way of thinking when
we speak of memory.

We must remember the integrated brain!

So in the end, what might all this mean for educators? How can we
apply it to help our students learn? Here are some key things to
remember.

Memory is personal
Memory can hide understanding
Memory is a tool
Use complex vs focused events to improve recall