Kobayashi and Schultz Flashcards
(18 cards)
What was the main question that Kobayashi and Schultz aimed to answer?
Whether temporal discounting occurs during the decision process when differently delayed rewards are compared, or during predictions of reward delays by Pavlovian conditioned stimuli without choice.
Describe the Pavlovian conditioning task used in the study
Visual stimuli were presented to the animals, with each stimulus associated with specific reward magnitudes and delays. The delay of reward was predicted by the conditioned stimulus (CS), allowing researchers to measure dopamine neuron responses without choice.
What was the purpose of the intertemporal choice task?
To assess how animals choose between sooner-smaller (SS) and later-larger (LL) rewards to determine and examine temporal discounting behavior.
What were the key parameters in the choice task?
SS rewards had fixed delays (2.0 seconds for animal A, 0 for animal B) and varying magnitudes. LL rewards had fixed magnitudes (0.56 ml for animal A, 0.58 ml for animal B) and varying delays (4, 8, or 16 seconds).
How did the researchers compare the exponential and hyperbolic models?
They fixed the discount coefficient k and derived A from the constraint that the value of immediate reward was 100%, then evaluated which model better fit the observed behavioral and neurophysiological data.
Which discounting model fit the behavioral data better and what does this suggest?
The hyperbolic model fit significantly better than the exponential model, confirming that reward value decreases less steeply for longer delays than for shorter delays.
How did dopamine responses to reward-predicting stimuli change with longer reward delays?
Dopamine responses to reward-predicting stimuli decreased with longer reward delays, following a hyperbolic pattern.
What were the components of the stimulus response?
The stimulus response had an initial non-differential component and a late delay-dependent reduction, suggesting dopamine neurons initially respond to reward signals generally but adjust based on delay.
How did reward magnitude affect dopamine responses to stimuli?
Larger rewards elicited stronger dopamine responses to stimuli than smaller rewards.
What does the stimulus response pattern suggest about how dopamine neurons encode value?
It suggests dopamine neurons encode subjective reward value by integrating both magnitude and delay information, even at the Pavlovian stage before active decision-making.
How did dopamine responses to the actual reward change with longer delays?
Dopamine responses to the actual reward increased with longer delays, showing an inverse effect to what was seen with the stimuli.
What are two possible explanations for increased dopamine responses to delayed rewards?
(1) Temporal uncertainty: reward timing might be more difficult to predict with longer delays; (2) Weaker associations: longer stimulus-reward intervals weaken associations, leading to incomplete reward predictions and positive prediction errors.
How does the optimal interval concept relate to the findings?
Delays of 8-16 seconds may exceed the optimal interval for forming strong stimulus-reward associations, resulting in weaker predictions and stronger dopamine responses at reward delivery.
How did reward magnitude affect dopamine responses to reward delivery?
Larger rewards elicited stronger dopamine responses than smaller rewards, even at the time of reward delivery.
How might this research provide insights into impulsivity?
Excessive discounting of delayed rewards leads to impulsivity; the study suggests that temporal discounting in the dopamine system may relate to behavioral impulsivity.
How does this research relate to the dual-system theory of decision making?
It supports the view that interaction between two different decision-making systems (one impulsive, one self-controlled) leads to dynamic inconsistency in intertemporal choice.
How does this study relate to prediction error theories of dopamine function?
The study supports that dopamine neurons encode reward prediction errors, showing that unexpected or incompletely predicted rewards (due to longer delays) cause stronger excitation.
How might this research inform strategies for promoting more far-sighted decision making?
Understanding the neural basis of temporal discounting could inform interventions that target dopamine-related pathways to reduce impulsive choices and promote consideration of long-term rewards.
