The Neurobiology of Addiction Flashcards
Where does the mesolimbic DA pathway originate and where does it project to?
From VTA
To limbic system (hippocampus, amygdala), NAc (ventral striatum), PFC
Where does the nigrostriatal DA pathway originate and where does it project to?
From SN
To dorsal striatum
Where does NAc receive inputs from and what are their roles?
PFC - action-outcome analysis
Ventral hippocampus - context
Amygdala - valence
VTA - mesolimbic DA pathway
What is the overall role of the striatum?
Decides action based on previous events (reinforcement)
What is the role of the dorsal striatum?
Habit and action patterns
What is the role of the ventral striatum?
Motivation and reinforcement
Where do D1R- and D2R-MSNs from the striatum converge?
Ventral pallidum
Which part of an MSN do DA inputs from the SN synapse onto?
Dendritic spine neck
Which part of an MSN do glutamatergic inputs from the cortex synapse onto?
Dendritic spine head
What is ‘wanting’, which NT does it involve, and which brain area is responsible?
Form of motivation to reach reward - appetitive
DA
Entire NAc shell
What is ‘liking’, which NT does it involve, and which brain area is responsible?
Pleasurable impact of reward consumption - stereotypical reflexive response - consummatory
Opiates
Hotspot on NAc shell
What is the prediction error theory of DA?
Firing of VTA neurons initially increases after reward (outcome)
Repeated pairing of cue and outcome shifts VTA firing increase to after cue - predictive
Baseline firing decreases if expected outcome does not occur
Firing to unpredicted outcomes and cues predicting outcomes - not predicted outcomes
DA provides prediction error signal - drives learning
How does the prediction error theory of DA explain drug addiction?
Addictive drugs increase mesolimbic DA
Generates inappropriate learning signal
Causes compulsive drug intake
What are the aspects of the triple coincidence in MSNs and what is its effect?
Glutamate stimulation, MSN depolarisation, DA release from VTA neurons
Causes MSN spine growth - plasticity
What is the incentive salience theory of DA?
DA assigns motivational salience originally elicited by reward to cue - makes cue itself desirable
How does the incentive salience theory of DA explain drug addiction?
Assigning incentive salience to cue makes cue harder to resist - decreases impulse control
What is the ramping theory of DA?
When series of actions required to reach reward - NAc DA increases gradually - signal gives continuous estimate of distance from reaching reward
DA provides sustained motivational drive
What is the role of the dorsolateral striatum?
Motor
What is the role of the dorsomedial striatum?
Cognitive
What is the allocation of limited resources theory of DA?
DA modulates resource allocation decisions - how worthwhile to expend limited internal resource
For NAc mesolimbic DA not required for simple fixed action to obtain reward - but required to drive effortful prolonged work for reward
