Dopamine

Question 1

Mesolimbic pathway

Answer 1

In the striatum, a small group of subcortical structures in the basal ganglia where especially the nucleus accumbens (ventral striatum) plas a role. Dopamine neurons in the ventral tegmental area (VTA) project ot the nucleus accumbens (NAcc/VS)

Question 2

Structural differences

Answer 2

Studies show lower density of dopamine D2 receptors in addicts.

Homeostatic account: Increased dopamine due to drugs is compensated by decreasing the D2 receptors (Consequence). Seen in animal studies, and the receptors can recover in abstinence

Reward deficiency syndrome (RDS) theory: Number of D2 receptors relates to individual differences in reward sensitivity, lower are at higher risk to develop addiction, and relatives of addicts show relatively low D2 density (cause)

Question 3

Cue reactivity

Answer 3

Pavlovian conditioning (stimuli predict reward) can evoke conditioned response and craving. Cue studies activate the NAcc

Question 4

Pavlovian learning, reward prediction (monkey study)

Answer 4

With cell recordings in the VTA and SN, the monkeys learned to predict delivery of fruit juice. At the start, there was a burst of BOLD signals at the unexpected reward.in the middle, both the CS-US At the end of training, the response is seen at the cue that predicts the reward CS (learned to expect)

Question 5

Reward prediction error

Answer 5

If the prediction is not yet completely accurate, you’re surprised and the reward prediction error occurs. Your brain says ‘ hey this is something nice, The value of the raeward doesn’t match the expected value. record this so we learn to predict it’. it’s an adaptive function of the brain to teach you the predictive cue. DA only fires at the cue, not the presentation of the reward.

Question 6

Temporal difference (abberant learning account)

Answer 6

Dopamine function in addiction: Over repeated drug use, the repetition of the DA signals continue to reinforce drug-related cues and actions to pathological levels.