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

COMMUNICATION

Reward Centers 112 113

The reward pathway is often called

a “pleasure pathway,” and dopamine

a “pleasure chemical,” but this is not

accurate. Dopamine in the nucleus

accumbens drives “wanting” of a

reward, but it is common for addicts

to experience strong cravings without

liking the effects of the drug. Pleasure

is likely to be caused by other

neurotransmitters such as opioids

or endocannabinoids.

WANTING VERSUS LIKING

Flooded with dopamine

Some drugs of abuse increase dopamine release, while

others stop it from being recycled. The buildup in the synapse

produces a large response in the brain, triggering the drive

to seek out more of the drug. Environmental cues become

linked with the drug and can trigger cravings in the future.

N

O

R

M

A

L^

R

ES

PO

NS

E

WHY IS JUNK

FOOD SO TASTY?

Most junk food contains

lots of sugar, salt, and fat,

which trigger our reward

system. This would have

helped us survive when

food was scarce.

T

O

LE

R

A

N

CE

Under tolerance

Over time, the brain reduces the number of dopamine

receptors to counteract the excess. Now, when normal

amounts of dopamine are released, they have little effect.

The user may need bigger and bigger doses of the drug to

feel its effect, and their desire for other rewards decreases.

Addiction

Most drugs of abuse cause huge amounts of dopamine to build up

in the reward system—far more than natural rewards like food or

sex. This creates a powerful drive to seek out more of the drug. It

also causes the brain to reduce the number of dopamine receptors,

so natural rewards no longer give the same sensation. This means

the user loses the urge to seek out things like food and social

engagement. Instead, drug cues become powerful triggers for

dopamine release, causing intense cravings, even when the user

consciously wants to stop and no longer enjoys the drug.

SYNAPSE

Dopamine

NEURON

POSTSYNAPTIC

RE

CEP

TOR

S

Vesicles in nerve

cell release

neurotransmitters

Many receptors

PRESYNAPTIC

NEURON

UP TO 60%

OF ADDICTION

RISK STEMS

FROM GENETIC

FACTORS

SYNAPSE

RE

CEP

TORS Not many receptors

POSTSYNAPTIC

NEURON

Normal

dopamine

release

Dopamine

PRESYNAPTIC

NEURON

US_112-113_Reward_Centers.indd 113 20/09/2019 12:36