45: Reward And Addiction Flashcards
Motivation
A process that mediates a goal-directed response to changes in external or internal environment
How does a surge of motivation trigger salience?
If a surge of motivation to consume a reward lasts beyond the time the individual is exposed to that cue -> triggers salience
Reinforcement
Consequence of operant (learned) behaviors that alter the probability that a behavior will be repeated under similar conditions each time
Aversion
Negative reinforcement of behavior, learning to avoid future encounters
Hedonia
Pleasure; subjectively positive sensation
Purpose of hedonia
Promotes behaviors consistent with survival of self and species
Salience
Something important in the surrounding environment worth paying attention to; the attention-grabbing feature of rewarding/valuable objects
Major nt involved in reward and pleasure
Dopamine
Three parts of a reward
- Hedonic effect
- Motivation to obtain the reward bc of its salience
- Associated learning
Reward learning: what neuron type and what they do
DA neurons: encode discrepancy between reward prediction and the actual reward received -> reward learning
Reward prediction error
Mismatch between actual events and the reward elicited
reward prediction error: difference btwn an unpredicted reward, a fully predicted reward, and omission of reward
- Unpredicted: activation (positive prediction error)
- Fully predicted: no response
- Omission of reward: depression (negative prediction error)
Drugs vs natural rewards in the RPE signaling
Drugs: repetition of RPE signals continues to reinforce drug-related cues and behaviors
Natural rewards: produce error-correcting RPE signals until the prediction matches the actual events
Examples of drugs that directly increase dopamine vs indirectly
Directly: coke, amphetamines, ecstasy
Indirectly: nicotine, alcohol, opiates, weed
How drugs are more powerful than natural rewards
They produce longer and larger increases in dopamine
Why do people tend to relapse in the environment where they’ve previously taken drugs?
Sensory stimulation associated with the drug causes an increase in dopamine levels
System involved in the dopamine hypothesis of reward
Mesolimbic system
Nucleus accumbens function**
Supresses sensation of pleasure/reward - keeps the brain in a reward-neutral state
What receptors does dynorphin bind in VTA
Kappa-opioid receptors
GABA and dynorphin function on VTA
Suppresses additional release of dopamine from VTA - halting reward process
Three areas of the reward system that drugs can hijack, causing increased dopamine levels?
VTA, NA, opioid system
What happens with chronic drug exposure in the reward pathway?
Alters morphology of neurons
Cellular changes related to chronic drug exposure
Drug alters expression of TFs and nts involved in dopamine release
Nt changes related to chronic drug exposure
Adaptations occur in glutamate, GABA, opioids, serotonin, and other nts
