the

Brain Mechanisms of Pleasure and Addiction

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[Laughter]

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you almost look like you're smiling a

bit are you Heath implanted electrodes

in the brains of chronically depressed

patients hoping to stimulate pleasurable

sensations penis ring you're smiling not

surprisingly the experiments were

controversial but the electrodes did

have an effect especially near an area

of the brain called the nucleus

accumbens Heath even led his patients

control their own stimulation how do you

feel I made a small joke yesterday I

don't know if I should repeat it or not

I'd like to hear very deep deep

electrode all the way down you're trying

to tell me how it excites you is that it

I think it's from one of the sexy button

yeah that why you said it went all the

way down

perhaps we get pleasure from drugs

because they stimulate the same brain

areas as sex and food

working in Montreal in the 1950s James

olds devised a crucial test he worked

out a new way to an effect ask animals

how they felt this is a device which

trains the animal to turn on the

stimulus for himself here you notice the

animal wandering toward the pedal when

he first touches it he gets no

stimulation it's not connected yet then

one time he touches the pedal it does

turn on the stimulation you can see the

light to go on now the interesting thing

about the old stimulation the rewarding

stimulation was the strength of it it

was somewhat different than rewarding

stimulation for food and water and that

there was no satiation animals would

continue for hours and hours and didn't

seem to satiate they didn't feel full

they would just keep doing it for long

long periods of time they would do it to

exhaustion Wow I will electrify the grid

the animal must cross an area that gives

a very painful chalk to the feet in

order to get to the pedal and stimulate

the brain and a rat wanting brain

stimulation would brave a shot stronger

than even a starving rat but brave to

get food willing to pay a very high

price in order to get to the pedal human

addicts will pay just as high a price

for their rewards the fascinating thing

was that we found in our laboratory that

every single drug that increased

sensitivity of the animal to brain

stimulation was either an abuse

substance or a substance that has

potential for abuse

so James olds technique of the 50s gave

scientists a way of testing for the

addictive potential of drugs and a way

to find out where in the brain they

acted and I think there's general

agreement

is the area where the action is in terms

of the rewarding effects of drugs

whether they be heroin whether they be a

feta me whether they be cocaine our

angel dust or whatever that when any

drug that produces rewarding effects

it's believed this is where the action

is using similar methods Chris pivoter

and his colleagues in Vancouver wanted

to know who which pleasure areas are

active when we crave both drugs and food

they found that the area he stimulated

in his patients the nucleus accumbens is

the center of a key Network the dopamine

circuit

Parowan seems to act in one way cocaine

in another

and both hit the nucleus accumbens which

the Canadian scientists recently proved

is also active when we crave food if we

selectively take these dopamine neurons

out of that part brain the animal loses

interest in self-administer and cocaine

it seems there's apparently the drug is

no longer reinforcing the same story

seems to apply for amphetamines if you

destroy these dopamine containing

neurons in the nucleus accumbens and

feta means self administration

disappears as well

a heroin addict has volunteered to be

given a large dose of morphine

chemically similar to heroin by

scientist at the National Institute for

drug abuse in Baltimore relax today

using new methods researchers can at

last start to look at where drugs act in

the human brain the new machines reveal

why different drugs make us act like

primitive animals morphine shuts down

the higher cortex and leaves the older

emotional brain in charge cocaine gives

a boost to the whole brain but

especially stimulates the primitive

centres of emotion so from those

rough-and-ready experiments in the 1950s

scientists did learn where in the brain

many addictive drugs act