You Can Learn to Remember: Change Your Thinking, Change Your Life pdfdrive com

how memories are created

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I
n order to understand how a memory is created, we need to have some idea of
how the brain functions. The human brain does not work the same way as a
computer – even though this has been one of the most popular analogies applied
to our brains in recent years. The computer is only a serial device – it deals with
one piece of data at a time, before moving on to the next. The brain, on the other
hand, can also act as a “parallel processor”, handling many pieces of information
simultaneously, and forging links between the items as it does so. A computer
memory keeps data in a precise location, tagged for easy retrieval; while the
brain appears to store memories in a less systematic way – the same memory
can, in theory at least, be retrieved from many different parts of the brain and by
many different routes. Some memories may not be accessible at all, because they
have been eccentrically labelled during storage and we do not know how to find
them. For example, I may have a clear memory of blowing out the candles on
my fourth-birthday cake, but no idea whatsoever who else was in the room as I
did so. One possible explanation for this is that my memory of the guests has not
been “filed” under birthday party, but under some other, unexpected, heading,
such as “people who have stared at me”.
However, in some ways the computer analogy is a helpful one. A memory
is stored as a result of electrical signals causing a change in the physical
structure of the brain, and similar electrical signals are involved in the recovery
of that memory. The moment we perceive – or recollect – anything, a short-term
memory of it is created (or recreated) in the form of a complicated sequence of
electrochemical impulses that are passed back and forth among a network of
neurons in the brain. The enormously complex pattern of this network, and the
varying frequencies at which the neurons pulse, play a major part in “encoding”
the memory. Indeed, the pattern in the network of neurons does not just represent
the memory, it is – literally – the memory. Far from being simply an elaborate
cipher experienced by the conscious mind, the pattern is an active ingredient of
consciousness (which, according to modern neuroscience, is only the sum of all
the electrical activity that occurs in the brain).
This process of apparent encoding is only possible because the brain is so
complex. The brain has billions of neurons, dendrites and synapses. The activity
of a single neuron could set off a cascade of impulses that can theoretically
course through the brain along more different pathways than there are atoms in
the universe.
The interactions between the neurons in a new short-term memory create a
pattern, or trace, that is quickly lost unless it is consolidated into a long-term
memory. Many different factors affect how likely it is that a short-term memory

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will be consolidated – for example, whether we are particularly stressed or
distracted. The process by which memory is consolidated appears to involve the
thalamus and a region near the centre of the brain called the hippocampus, which
we can think of as providing energy for the creation of long-term memories in
other parts of the brain.
Memory consolidation relies upon the plasticity of the brain – the way that
it is continuously modifying itself. We have already seen that an active memory
is a pattern of electrical impulses passing around a group of neurons. Making
long-term memories involves changing the physical characteristics of the brain –
including increasing the number of synapses along the desired route – so that
some patterns are more easily activated, or excited, than others. The easier a
pattern is to generate and regenerate, the more easily the associated memories
are created and recalled.
When a neurotransmitter is passed across a synapse, it does not just
stimulate an electrical signal in the dendrite. It also stimulates the production of
ribonucleic acid (RNA), which, among other things, controls the manufacture of
proteins in the brain cell. Recent research has led scientists to believe that the
proteins that are synthesized in the cell are used to build extra and larger
synapses on the excited dendrites, thereby making the dendrites even easier to
excite in future (thus consolidating that particular memory). The physical
memory traces created through such permanent changes in the brain’s structure
are sometimes known as engrams.