Padoa-Schioppa and Assad - "Neurons in the orbitofrontal cortex encode economic value" Flashcards
(16 cards)
What are the three main types of neuronal responses found in the OFC? And what % of neural responses did they explain?
Offer value, chosen value, and taste. These three variables explained 79% of the neuronal responses observed.
What is a “chosen value” neuron?
A neuron that responds to the subjective value of whatever juice the monkey selected, regardless of which specific juice it was.
What is an “offer value” neuron?
A neuron that responds to the value of a specific juice being offered, regardless of whether that juice was ultimately chosen.
What does a “taste” neuron encode?
A taste neuron responds to the type of juice selected (e.g., apple vs. peppermint tea), regardless of its amount or value.
What is the significance of U-shaped neuronal responses?
U-shaped responses indicate neurons that encode the relative subjective value of the chosen juice. Activity is high when either juice is strongly preferred and low when options are close in value.
How were “offer value” and “chosen value” dissociated in the experiment?
By analyzing trials where the monkey chose the less valuable juice (choosing B when A is actually more valuable), researchers could separate neurons that responded to what was offered versus what was actually chosen.
What evidence supports that OFC neurons encode economic value rather than visual properties?
Similar visual stimuli that represented different economic values (e.g., offer types 1B:3A and 1B:1A) resulted in different neural responses. Additionally, visually different stimuli with similar economic values elicited similar responses.
What is a “goods-based model” of decision-making?
A model where economic choices are made between goods themselves. The brain assigns values to available options, compares these values, and only then plans the appropriate motor action.
What is an “action-based model” of decision-making?
A model where economic choices are made between potential actions. The brain would assign values to different possible actions rather than to goods themselves.
What was the basic experimental design?
Monkeys chose between different amounts of two juice types presented as colored squares. The color indicated juice type, and the number of squares indicated amount. Monkeys made choices through eye movements while researchers recorded OFC neuron activity.
What mathematical relationship was found for U-shaped neuronal responses?
For neurons with U-shaped responses, the slope ratio (k) was equal to the relative value of the juices (n), confirming these neurons were encoding economic value.
How did researchers determine the subjective value that monkeys assigned to different juices?
By observing choice patterns across different juice offers. For example, if a monkey consistently chose 1 drop of juice A over 3 drops of juice B, they could calculate that 1A ≈ 3B (one drop of juice A is valued approximately equal to three drops of juice B).
What does the finding that neurons encode “chosen value” even before juice delivery suggest?
It suggests that the brain computes the value of the chosen option during the decision process, not just as a response to reward consumption.
Why is the OFC particularly well-suited for economic decision-making?
The OFC receives inputs about various sensory properties of goods and has connections to brain regions involved in reward processing, making it ideally positioned to integrate information about goods’ values.
What is the significance of finding that adding more variables beyond the main three did not significantly improve the regression?
It suggests that economic decision-making in the OFC is remarkably efficient, requiring only a few key variables to represent complex choices.
How does this research connect neuroscience with economic theory?
It provides a neural basis for utility theory and rational choice theory in economics by showing how the brain actually computes and compares subjective values when making decisions.
