Neurophysiology Of Reward And Addiction Flashcards
What does reward drive?
incentive based learning, appropriate response to stimuli, and development of goal directed behavior
What NTR plays a key role in processes modulating reward seeking behaviors?
Dopamine
How does dopamine arrive at the hypothalamus?
a. Medial forebrain bundles carries dopaminergic fibers from vetnral tegmental area (VTA) of midbrain to Nucleus Accumbens
b. All structures —> hypothalamus
Where else do VTA projections go and influence?
What will this cause?
hippocampus, amygdala, and prefrontal cortex
Prefrontal cortex —> feedback to VTA (directly or thru nucleus accumbens)
What initiatives the Neuroendocrine and visceral response to reward?
Hypothalamus
What is motivation in human behavior?
◦ Process that mediates goal-directed responses or goal-seeking behavior to changes in external or internal environment
What is reinforcement in human behavior?
consequence of learned behaviors that alters probability that a behavior will or will not be repeated under similar conditions each time
What is Saliency?
◦ Impt. Thing in surrounding environment worth paying attention to
What is a reward for human behavior?
◦ Objects, stimuli, or activities that have positive value
What is aversion in human behavior ?
◦ Negative reinforcement of behavior - teaches individual to avoid future encounters
What is pleasure in human behavior?
What is the physiologic purpose of it?
◦ Positive sensation; referred to as euphoria or hedonia
◦ Physiologic purpose:
‣ Promote behaviors consistent w/ survival of self and the species
What is a Reward Prediction error?
Measure of how much the expected value of a reward differs from the actual reward being received.
What is a positive reward prediction error result from?
When an unanticipated reward is received
if one predicts a minimal reward, yet experiences a larger reward
When would a negative reward prediction error occur?
What is this associated with?
when a reward is expected, yet a minimal reward is received
Depressive response
When would the Reward Prediction Error not be activated?
If a reward is anticipated and an equally stimulating reward is received, (aka, a fully predicted reward is received)
What type of RPE will drug use initially cause?
Positive RPE
What happens with Repeated Drug use in terms of RPEs?
the repetition of these reward prediction error signals the reinforcement of continued drug-released consumption (or exposure to drug-related cues, behaviors, and environments).
These unnatural exposures set up the brain for a reward prediction error that learns over time to formulate better predictions of the future.
What encodes for the difference between reward received and predicted (aka the RPE)?
Dopamine
involved in the prediction of reward, assignment of salience, and behavioral learning that occurs.
What does the extracellular dopamine released in the Limbic systems and other reward centers by drugs of abuse do?
motivates further procurement of more drug
(regardless of whether or not the effects of the drug are consciously perceived to be pleasurable
When do natural re-enforcers of reward cease dopamine signaling?
Compared to Drugs of Abuse?
once the activity/event concludes.
drugs of abuse continue to increase dopamine signaling unnaturally after event is done.
exacerbates the reward prediction error compared to a natural RPE.
What will natural rewards produce?
Error correcting Dopamine-RPE signals
Will act until predictions match actual events
When given a choice between event leading to drug and event leading to natural reward what will an individual exposed to a Drug of Abuse do?
Develop bias toward drug that will strengthen with each drug use
How do Drugs of Abuse reinforce their use?
increase Extracellular dopamine concentration in Limbic regions (incl. Nucleus Accumbens)
◦ Increase it for longer and larger (5-10 fold) than natural rewards (food or sex)
Which drugs of abuse increase dopamine directly? How?
Cocaine, amphetamine, methamphetamine, and ecstasy
Inhibit DA reuptake
Promote DA release
