Dopamine and Reinforcement Flashcards
(17 cards)
What do self-stimulation studies reveal about dopamine and motivation?
- Rats will press a lever to stimulate dopamine neurons in the VTA until exhaustion.
- Optogenetic activation of VTA dopamine neurons also drives persistent lever pressing.
- Suggests dopamine drives motivated behaviour, not just pleasure.
What is the role of dopamine in motivation and learning?
- Signals reward prediction error
- Facilitates associative learning
- Drives motivational salience - attention and goal-directed action toward meaningful stimuli
What are the three primary dopamine pathways?
- Mesocortical: VTA → Cortex (cognition).
- Mesolimbic: VTA → Limbic system (reward, motivation).
- Nigrostriatal: Substantia Nigra → Striatum (motor control).
What do dopamine self-stimulation experiments show?
Animals self-stimulate dopamine pathways, indicating dopamine mediates ‘wanting’ (motivation) for reward.
What did Wise et al. (1978) conclude about dopamine and motivation?
Dopamine antagonists reduce the effort (lever pressing) for food reward, suggesting dopamine drives motivation (‘wanting’) to obtain rewards.
How does Barbano & Cador (2006) contest the anhedonia hypothesis of dopamine antagonists?
Animals on dopamine antagonists still showed ‘liking’ for sweet solutions, but wouldn’t ‘work’ for them. This separates dopamine’s role in ‘wanting’ from ‘liking.’
How does the Schultz et al. (1997) study explain dopamine’s role in learning?
- Dopamine neurons signal ‘reward prediction error’ to drive learning:
- Fire when reward is unexpected.
- Shift to fire for cues predicting reward after learning.
- Reduce firing when cues predicting reward fail.
What is the contemporary understanding of dopamine’s function?
Dopamine functions as a reward prediction error signal, primarily driving motivation and learning.
What is dopamine’s role in attention?
- Arousal and alertness.
- Directing attention to important stimuli.
- Maintaining focus and cognitive control.
What are the main symptom categories of schizophrenia?
- Positive Symptoms: Hallucinations, delusions, disorganized thought.
- Negative Symptoms: Reduced motivation, flat affect, social withdrawal.
- Cognitive Symptoms: Impaired attention, memory, and executive function.
Explain the dopamine hypothesis of schizophrenia.
- Increased dopamine activity and D2 receptor sensitivity.
- Leads to over-inhibition of the striatal ‘NO-GO’ pathway.
- Results in difficulty suppressing inappropriate thoughts/behaviours (positive symptoms).
How is latent inhibition (LI) disrupted in schizophrenia?
- LI is the passive ability to ignore previously irrelevant stimuli.
- SCZ patients show impaired LI, struggling to ignore irrelevant stimuli.
- Suggests a deficit in attentional filtering.
What are the two main dopamine receptor families?
- D1-like (D1, D5): Gs-coupled, generally excitatory.
- D2-like (D2, D3, D4): Gi-coupled, generally inhibitory.
Explain the neurobiology of schizophrenia in the striatum.
- Excess dopamine in the striatum.
- Over-activates D2 receptors, over-inhibiting the ‘NO-GO’ pathway.
- Impairs ability to inhibit responses, contributing to positive symptoms.
How does ADHD’s dopamine disruption contrast with schizophrenia?
- ADHD: Often involves hypodopaminergia (too little DA) in the prefrontal cortex, affecting attention and impulse control.
- Schizophrenia: Involves hyperdopaminergia (too much DA) in the striatum, mainly affecting D2 receptors and leading to positive symptoms.
How do antipsychotics primarily reverse some schizophrenia symptoms?
- They block D2 dopamine receptors.
- This disinhibits the ‘NO-GO’ pathway.
- Improves response inhibition and reduces positive symptoms.
