NAB-Reward, pleasure and desire

Reward=object/event that elicits approach and is worked for.
It is associated with wanting and liking.
Wanting=feeling of desire and approach behaviours
Liking=feeling of pleasure (explicit liking) and other objective responses (implicit liking)
Alterations in the brain substrates of reward-related processes are likely mechanisms underlying addiction.

Classical techniques to identify brain substrates of reward:

Nucleus accumbens

In rats:

Rewarding stimuli increase dopamine transmission in NAC, animals work to increase dopamine stimulation within NAC, and dopamine antagonists block behavioural effects of rewards.
NAC dopamine causes pleasure and desire.

Similarly, in humans, nucleus accumbens dopamine release during reward anticipation.

>In the Meso-corticolimbic dopamine system:

• rewards increase NAC dopamine
• systemic and intra-NAC dopamine antagonists block responses normally maintained by reward

>Cholinergic projection from PPTg to VTA:

• electrical self-stimulation
• Cholinergic drugs are self-administered into VTA

>Glutamate projections from mPFC to VTA:

• electrical self-stimulation
• stimulate dopamine release in NAC

How much one works for reward may not directly reflect the liking or pleasure induced by the reward, but rather wanting of or desire for the reward.

Overlap between brain substrates of positive and negative emotions:

Brain substrates of emotional states associated with aversive stimuli and appetitive stimuli habe originally been studied seperately, but more recently it has come to the fore that there is an overlap.

• Dopamine and nucleus accumbens play important roles in fear-related processes, in adition to loe in reward-related states and responses.
• Amygdala, apart from playing key role in fear-related responses, ahs also been implicated in responses to appetitive stimuli.

A common currency of emotoion may enable brain to generate adaptive responses baed on integrated assessment of positive and negative stimuli.
Brain substrates such as dopamine, nucleus accumbens and amygdala may not play specific role in emotion per se, but may contribute to fundamental cognitive processes that are associated with both aversive and appettitive stimuli (e.g. salience signalling and attention or associative learning).