Substance use disorders Flashcards
What does striatum consist of?
Dorsal striatum?
Ventral striatum?
Striatum = caudate, putamen, and NA
Dorsal striatum = corpus striatum = caudate + putamen
Ventral striatum = NA
BG –> thalamus –> ???
Cortex involved in action, such as motor cortex and premotor association cortex
What parts of cortex project to NA?
PFC, amygdala, and hippocampus
What type of cell makes up the striatum?
Medium spiny neuron. 1 cell has 10,000 inputs. Integrates glutamatergic cortical info and DA info from midbrain. GABAergic.
Reinforcement
Outcome of a behavior increases likelihood that behavior will be repeated. Negative reinforcement ex: rat presses lever to avoid shock
Reward
Subjective emotional experience (pleasure, euphoria, hedonia) that accompanies positive reinforcement
Impulsive behavior
What is a chemical sign of impulsivity?
Tendency to consistently choose immediate reinforcement, and impairment in ability to inhibit a course of action once initiated.
•Inheritance of impulsivity is marked by low levels of serotonin metabolites.
Compulsive behavior
Perseveration in behavioral strategy even in face of unsuccessful or adverse outcomes.
Mesolimbic DA system
Highly involved in reward. VTA → NA mediates motor effort to obtaining wanted goals. Blocking DA receptors w/ drugs blunts the brain-stimulation reward in rats. More stimulation is required.
Reward error prediction hypothesis
DA is important for learning about rewards. Firing of DA neurons occurs:
•The 1st time the organisms experiences a new primary reward
•When observing stimuli that reliably predict expected reward
•When a previously experienced reward is better than predicted
•DA neurons fire in response to reward early in training. Once trained, DA neurons fire in response to reward-predicting stimulus, but not the reward itself.
•DA released if reward comes earlier or later than expected. Learning. No release if reward comes at the expected time.
Incentive-sensitization hypothesis
Drug use causes long-lasting SENSITIZATION of DA’s ability to produce drug WANTING, even while drug liking may be decreasing.
Reward-error prediction hypothesis
Enhanced DA release during drug taking produces a condition in which all stimuli are experienced as BETTER THAN EXPECTED. This theory does not require drug to produce state of euphoria.
Impulsivity occurs w/ impairment of what?
PFC
What part of brain controls compulsive behavior?
Compulsivity occurs due to shift from PFC-NA motor circuits to an emphasis on dorsal striatal control. Dorsal striatum controls habits.
Cycle of addiction
Preoccupation / anticipation → binge / intoxication → withdrawal / negative effects
Repeat
