Reward and Drugs

Brain Development

Reward system is in place before prefrontal cortex develops -> we are very susceptible to reward early on before we get conscious cognitive control over stimuli that may be rewarding

Reward Based Learning

When we are rewarded for a behaviour we are likely to repeat it

Rewards that we are exposed to now have huge amounts of dopamine, not necessarily what our brains were designed for and and it makes it quite difficult to counter those.

The basis of a lot of addictive behaviours.

How does addiction hijack the brain?

Turns off the PFC and leaves you in the Older (middle) brain (reward system).

Judgment becomes distorted and the brain starts to treat the substance as necessary for survival.

It is not a failure of moral judgement or poor will power

Intracranial self stimulation (ISS) of the brain

Certain brain regions will keep an animal pressing a button or performing a behaviour to get the stimulation. Examples are the hypothalamus and the Medial Forebrain Bundle (MFB).

Medial Forebrain Bundle (MFB)

Reward pathway

Releases dopamine from the ventral tegmental area, through the hypothalamus, through the basal ganglia, including the nucleus accumbens the amygdala all the way to the prefrontal cortex

Dopamine is the basis of reward

Model of Addiction

1. Binge/Intoxication

2. Withdrawl/Negative Affect

3. Preoccupation/Anticipation

Binge/Intoxication

Ventral tegmental area (VTA), Nucleus accumbens, striatum (basal ganglia)

Reward and incentive salience

Withdrawl/Negative Affect

Amygdala, habenula, Bed nucleus of the stria terminalis (BNST)

Negative emotional states (dysphoria, anxiety, irritability, malaise) and stress

Preoccupation/Anticipation

PFC, insula, anterior cingulate

Craving, impulsivity, EF dysfunction