Lecture 18 - Motivation Flashcards
Motivation
construct used to explain variability and flexibility in behavior output attributable to external stimuli and internal states
- appetitively motivated behaviors: goal of attaining psoitive objects or envi consequences (food, water, sex)
- aversively motivated behaviors: prevent/terminate negative stimuli
Basal ganglia circuitry
input from cortical mantle –> striatum –> palladium –> thalamic
-indirect vs. direct pathway
Nucleus accumbens
ventral, medial, anterior aspect of basal ganglia
- part of the “limbic” CSPT circuit
- innervated by ascending dopamine pathways
- medium-spiny neurons receive NT signal and integrate multiple complex neurochemically specified inputs
Dopamine
modulates glutamate signals at spiny neurons
CPST loop
prefrontal cortex/amygdala/hippocampus –> nucleus accumbens –> ventral pallidum –> MD thalamus –> cortical motor-planning regions
- parallel loops from distict cortical areas
- palladial level of BG also outputs directly to brainstem
- specialized for motivationally relevant info
Ventral tegmental
strongest self-stimulation behavior
- input to hippocampus
- dopamine-rich = reward
“wanting”
dopamine regulated
-identify salient reinforcers and pursue them
-go after something
-important for learning about rewards:
> The 1st time experiencing new reward
> observing stimuli that reliably predicts award ***
> when previous reward is better than predicted
-dopamine firing early in training is direct response to reward
-dopamine firing later in training associated with stimulus that predicts reward
“liking”
opioid regulated
-subjective emotional experience of pleasure upon interacting with reinforcer
Tolerance
progressively diminished phys response to drug with repeated exposure (right shift of dose-effect fx)
-opposite: sensitization
Dependence
phys state induced by repeated exposure to drug where drug presence is necessary for normal function
Craving
subjective state of intense desire for particular goal
Addiction
- loss of control over limiting intake
- habit persists despite negative consequences
- narrowing of other activities
- potential for relapse throughout life-span
Withdrawal
homeostatic adaptation to drug = tolerance, and absence of drug = withdrawal
-expressed as physical symptoms or psychological symptoms
Opponent process theory
-rush/euphoria peak gets smaller over time due to adaptation, as does peak of withdrawal (gets worse)
Incentive-sensitization hypothesis
learning-based theory of addiction
-drug use leads to long-lasting sensitization of dopamine’s ability to produce drug “wanting”
Reward-error prediction hypothesis
learning-based theory of addiction
-enhanced dopamine release during drug taking produces a condition in which ALL stimuli encountered during drug use are experienced as being “better than expected”
Impulsive behavior and addiction
2 relevant features:
- tendency to consistently choose immediate reinforcement over delayed gratification, even when immediate reinforcement is smaller or less beneficial
- impairment in ability to inhibit a course of action once initiated
- excessive “wanting” of drugs or drug-related stimuli, such that inhibitory control is overwhelmed
- impaired PFC function (nucleus accumbens gets input from PFC –> controls impulsivity, so if compromised lose inhibitory control so abnormal accumbens fx)
Compulsive behavior and addiction
repeat/prolong certain behavior strategy even in face of unsuccessful or adverse outcomes
- in addiction, individuals often report “wanting’ the drug more even though they “like” it less. They also “want” the drug despite adverse outcomes
- shift from prefrontal-accumbens motor circuits to emphasis on dorsal striatal control
- dorsal striatum mediates compulsive “habits”
Addiction cycle
- preoccupation/anticipation
–> (persistent desire, larger amounts taken than expected) 2. binge/intoxication
–> (tolerance, withdrawal, compromised social, occupational or recreational activities) - withdrawal/negative affect
–> preoccupation with obtaining, persistent physical/psych problems
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