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

136

MEMORY, LEARNING, AND THINKING

How a Memory Forms 137

Both neurons firing repeatedly at the same time causes a

chemical cascade within the second cell (see p.26), which

makes it more sensitive to the neurotransmitter, and causes extra

receptors to migrate to the edge of the synapse. A signal travels

back to the first cell, telling it to produce more neurotransmitters.

Now, a single action potential causes the release of

more neurotransmitters, carrying the message quickly

and efficiently across the synapse, where it is received by

many receptors. This makes it easier for the second neuron

to be activated, sending its electrical signal onward.

2 3

D

U

R

IN

G

L

EA

RN

IN

G

A

F

T

ER

L

EA

RN

IN

G

Emotional memories

When something strongly emotional happens, whether that is good or bad,

stress chemicals such as adrenaline and noradrenaline are released. These

make it easier for long-term potentiation to occur with fewer repetitions.

This explains why emotionally arousing memories are stored more rapidly

in the brain and why they are easier to recall than nonemotional memories.

1

Hormone released

Noradrenaline released

by neurons originating in the

locus coeruleus triggers a cascade

of changes within cells in

the hippocampus.

More

receptors

move to

membrane

surface

More receptors

on receiving

cell

Phosphates guide

receptors to insert

themselves next to synapse

Neurotransmitter

released

More neurotransmitters

produced and

released

Repeated activation causes

more neurotransmitters

to be released

Strong

connection

allows

signal to

pass quickly

Neurotransmitter

Phosphate

2

Strong connection

An enzyme adds

phosphate groups to receptors

in the postsynaptic neuron. This

makes it easier for more receptors

to be inserted in the cell membrane,

so the connection is strengthened

and the memory forms easily.

Noradrenaline

released by neurons

in locus coeruleus,

located in pons

LOCUS

COERULEUS

PONS

Changes

triggered in

hippocampal

neurons

Action potential

triggered in

second neuron

HIPPOCAMPUS

KEY

Neuron is

primed for

connection

Action potential

triggered easily

Action potential in

presynaptic neuron triggers

neurotransmitter release

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