How the Brain Works The Facts Visually Explained by DK (z-lib.org)

MEMORY, LEARNING, AND THINKING

How a Memory Forms

How a

Memory Forms

When networks of neurons in the brain are

repeatedly activated, changes in the cells

strengthen their connections, making it easier

for each to activate the next (see pp.26–27). This

process is known as long-term potentiation.

Strengthening connections

When you repeatedly activate a group of neurons—by practicing a

skill or revising facts, for example—they begin to change. This is how

we form long-term memories (see p.135) in a process called long-term

potentiation, which depends on various mechanisms taking place

in brain cells. The first (presynaptic) neuron makes more

neurotransmitters release when the signal reaches it, and the second

inserts more receptors into its membrane. This speeds up transmission

at the synapse. Something like driving a car, which seems complex

when you start, can become effortless as the neural pathways involved

become more efficient. If this paired activation is repeated enough, new

dendrites can grow, linking the two neurons via new synapses, giving

the message alternative pathways and helping it travel even faster.

Firing together

Long-term potentiation

occurs across the brain but

has been best studied in the

hippocampus. Electrical signals

travel along a neuron’s axon to

the synapse, where chemical

messengers are released.

Memories of sounds

are stored partly in or

near auditory cortex

Before learning, only a weak connection exists between

neurons. One action potential (pulse of electrical current)

from the first cell releases only a small amount of neurotransmitters,

and this may or may not be enough to activate the next neuron,

which has just a few receptors.

1

B

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LE

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Scientists have recently been able to

pinpoint a precise memory trace in

someone’s brain. In general, memories

tend to be stored near the area of the

brain that relates to how they were

formed. For example, memories for

voices would be near the language

centers, and things that you have

seen are stored, at least partly,

near the visual cortex.

MEMORY TRACES

Vesicle containing

neurotransmitters

Second

nerve cell

DE

ND

RIT

E

AX

ON

SYN

AP

SE

NERVE CELL

BODY

SYNAPSE

Nerve cell in

hippocampus fires a

signal to a receiving cell

Electrical signal

travels along axon

MORE THAN 100 DIFFERENT of sending neuron

NEUROTRANSMITTERS

HAVE BEEN IDENTIFIED

A

XO

N

AUDITORY

CORTEX

VISUAL

CORTEX

Action potential

triggers release of

neurotransmitter

US_136-137_How_memory_forms.indd 136 20/09/2019 12:36