Task 4 Flashcards
(30 cards)
What are two key observations (illnesses etc.) that have historically dominated the understanding of dopamine function?
Severe movement deficits after dopamine-depleting lesions in Parkinson’s disease patients and reduced behavioral responses to motivating stimuli after interference with dopamine neurotransmission in experimental rats
How is dopamine activity related to rewards?
Dopamine activity, as measured by electrophysiology or voltammetry, shows substantial increases related to rewards and reward-predicting stimuli
How does dopamine respond to reward uncertainty?
A slower, distinct electrophysiological response encodes the uncertainty associated with rewards
How do aversive events affect dopamine responses?
Aversive events produce slower electrophysiological dopamine responses, predominantly depressions
What information does dopamine neurotransmission provide to the brain?
It provides differential and heterogeneous information to subcortical and cortical brain structures about essential outcome components for approach behavior, learning, and economic decision-making
How is the function of rewards defined?
By their action on behavior, not by affecting the brain through specific sensory receptors
What do identified midbrain dopamine-mediating signals signify?
They signify the pure reward value of objects, irrespective of their sensory components or the behavioral functions necessary to obtain them
What constitutes the reward-prediction error in dopamine signaling?
The difference between predicted and obtained rewards,
crucial for reward-driven learning according to the Rescorla-Wagner learning rule
What is phasic activation in midbrain dopaminergic neurons?
Burst activity following primary food and liquid rewards, coding for the prediction error:
- such that an unpredicted reward elicits activation (positive prediction error)
- omission of a predicted reward induces a depression (negative prediction error)
What indicates the importance of prediction errors for learning?
The block paradigm
shows that a stimulus is not learned as a valid reward-predicting stimulus if it is paired with an already fully predicted reward
What happens in the conditioned inhibition paradigm regarding dopamine responses?
- A test stimulus presented with an established reward-predicting stimulus
- but no reward results in the test stimulus predicting the absence of reward,
- not producing a dopamine-mediated response
How do dopaminergic neurons code reward-prediction errors?
Dopamine response equals reward occurred minus reward predicted
What might the dopamine-mediated response to rewards constitute?
A neural basis of prediction error, conveying the crucial learning term of the Rescorla-Wagner learning rule
What might dopamine-mediated signals influence in postsynaptic neurons?
Short- and long-term modifications of corticostriatal synaptic transmission
How might prediction errors contribute to behavior?
By establishing predictions, comparing current inputs with previous predictions, and emitting a prediction-error signal if a mismatch is detected
How are responses to prediction errors graded?
Partial prediction errors induce smaller error responses, and responses co-vary with both magnitude and probability of reward
How does the dopamine-mediated prediction-error response adapt over time?
It adapts to the mean and variance of the predicted probability distribution of reward magnitudes within the 2s stimulus-reward intervals
What roles do reward-predicting stimuli play?
- predict outcomes,
- provide advance information for decision-making,
- generate approach behavior
- serve as positive, conditioned reinforcers for earlier stimuli and actions
How do dopaminergic neurons respond to neutral and aversive stimuli?
They show generalized activation-depression responses if these stimuli are not distinctively different from reward predictors
How is the reward prediction error signal conveyed in humans?
brain areas
It is conveyed to both the striatum and cortical areas, playing a central role in learning to optimize behavior
What role does the dopaminergic system play in learning?
It helps make predictions based on past experiences, updating predictions when violated using a reward prediction error signal
What do reinforcement learning models provide in terms of dopamine hypotheses?
A parsimonious account of many behavioral phenomena and neural activation patterns
What does human fMRI indicate about dopamine?
fMRI activations at or near dopaminergic midbrain nuclei and the ventral striatum correlate with both reward expectation and reward prediction errors
How is the ventral striatum (VS) activated during learning trials?
The VS is activated during both expectation and receipt of rewards, with potentially stronger activations during the receipt phase
