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Reward value coding distinct from risk attitude-related uncertainty coding in human reward systems.

Tobler PN, O'Doherty JP, Dolan RJ, Schultz W - J. Neurophysiol. (2006)

Bottom Line: Participants discriminated behaviorally between stimuli associated with different expected values and uncertainty.Stimuli associated with higher expected values elicited monotonically increasing activations in distinct regions of the striatum, irrespective of different combinations of magnitude and probability.Stimuli associated with higher uncertainty (variance) elicited increasing activations in the lateral orbitofrontal cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK. pnt21@cam.ac.uk

ABSTRACT
When deciding between different options, individuals are guided by the expected (mean) value of the different outcomes and by the associated degrees of uncertainty. We used functional magnetic resonance imaging to identify brain activations coding the key decision parameters of expected value (magnitude and probability) separately from uncertainty (statistical variance) of monetary rewards. Participants discriminated behaviorally between stimuli associated with different expected values and uncertainty. Stimuli associated with higher expected values elicited monotonically increasing activations in distinct regions of the striatum, irrespective of different combinations of magnitude and probability. Stimuli associated with higher uncertainty (variance) elicited increasing activations in the lateral orbitofrontal cortex. Uncertainty-related activations covaried with individual risk aversion in lateral orbitofrontal regions and risk-seeking in more medial areas. Furthermore, activations in expected value-coding regions in prefrontal cortex covaried differentially with uncertainty depending on risk attitudes of individual participants, suggesting that separate prefrontal regions are involved in risk aversion and seeking. These data demonstrate the distinct coding in key reward structures of the two basic and crucial decision parameters, expected value, and uncertainty.

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Coding of reward magnitude and probability in striatum. A: activation in caudate covarying with increasing reward magnitude (peak at –12/2/6; Table 2, top). B: time courses of responses to stimuli associated with different reward magnitudes, averaged across 16 participants. C: regression of averaged activation on magnitude (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in B. D—F: same as A–C but with time courses separated according to reward being delivered or not. G: activation in ventral striatum covarying with increasing probability (peak at –10/4/−4; Table 2, middle). H: time courses of responses to stimuli associated with different probabilities, averaged across 16 participants. I: regression of average activation on probability (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in H. J–K: same as G–I but with time courses separated according to reward being delivered or not. In this and all other figures, the right side of the image corresponds to the right side of the brain and circles around activations serve as visual aid.
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f2: Coding of reward magnitude and probability in striatum. A: activation in caudate covarying with increasing reward magnitude (peak at –12/2/6; Table 2, top). B: time courses of responses to stimuli associated with different reward magnitudes, averaged across 16 participants. C: regression of averaged activation on magnitude (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in B. D—F: same as A–C but with time courses separated according to reward being delivered or not. G: activation in ventral striatum covarying with increasing probability (peak at –10/4/−4; Table 2, middle). H: time courses of responses to stimuli associated with different probabilities, averaged across 16 participants. I: regression of average activation on probability (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in H. J–K: same as G–I but with time courses separated according to reward being delivered or not. In this and all other figures, the right side of the image corresponds to the right side of the brain and circles around activations serve as visual aid.

Mentions: To first locate activations reflecting magnitude and probability, we regressed responses to reward-predicting stimuli separately against increases in these two parameters. We found significant correlations with brain activity for both parameters in caudate and ventro-medial putamen (Fig. 2, A and G). Similar increases were seen in the time courses of activations averaged across all participants (Fig. 2, B and H) and with regressions of average activations onto magnitude and probability (Fig. 2, C and I). These correlations were similar when the data were analyzed separately in rewarded and unrewarded trials (Fig. 2, D–F and J–L). In addition, a medial prefrontal region showed increasing activations only with probability but not magnitude, as described before (Knutson et al. 2005).


Reward value coding distinct from risk attitude-related uncertainty coding in human reward systems.

Tobler PN, O'Doherty JP, Dolan RJ, Schultz W - J. Neurophysiol. (2006)

Coding of reward magnitude and probability in striatum. A: activation in caudate covarying with increasing reward magnitude (peak at –12/2/6; Table 2, top). B: time courses of responses to stimuli associated with different reward magnitudes, averaged across 16 participants. C: regression of averaged activation on magnitude (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in B. D—F: same as A–C but with time courses separated according to reward being delivered or not. G: activation in ventral striatum covarying with increasing probability (peak at –10/4/−4; Table 2, middle). H: time courses of responses to stimuli associated with different probabilities, averaged across 16 participants. I: regression of average activation on probability (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in H. J–K: same as G–I but with time courses separated according to reward being delivered or not. In this and all other figures, the right side of the image corresponds to the right side of the brain and circles around activations serve as visual aid.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2637604&req=5

f2: Coding of reward magnitude and probability in striatum. A: activation in caudate covarying with increasing reward magnitude (peak at –12/2/6; Table 2, top). B: time courses of responses to stimuli associated with different reward magnitudes, averaged across 16 participants. C: regression of averaged activation on magnitude (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in B. D—F: same as A–C but with time courses separated according to reward being delivered or not. G: activation in ventral striatum covarying with increasing probability (peak at –10/4/−4; Table 2, middle). H: time courses of responses to stimuli associated with different probabilities, averaged across 16 participants. I: regression of average activation on probability (16 participants). Activations are further averaged across 2nd and 3rd (peak) time points shown in H. J–K: same as G–I but with time courses separated according to reward being delivered or not. In this and all other figures, the right side of the image corresponds to the right side of the brain and circles around activations serve as visual aid.
Mentions: To first locate activations reflecting magnitude and probability, we regressed responses to reward-predicting stimuli separately against increases in these two parameters. We found significant correlations with brain activity for both parameters in caudate and ventro-medial putamen (Fig. 2, A and G). Similar increases were seen in the time courses of activations averaged across all participants (Fig. 2, B and H) and with regressions of average activations onto magnitude and probability (Fig. 2, C and I). These correlations were similar when the data were analyzed separately in rewarded and unrewarded trials (Fig. 2, D–F and J–L). In addition, a medial prefrontal region showed increasing activations only with probability but not magnitude, as described before (Knutson et al. 2005).

Bottom Line: Participants discriminated behaviorally between stimuli associated with different expected values and uncertainty.Stimuli associated with higher expected values elicited monotonically increasing activations in distinct regions of the striatum, irrespective of different combinations of magnitude and probability.Stimuli associated with higher uncertainty (variance) elicited increasing activations in the lateral orbitofrontal cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK. pnt21@cam.ac.uk

ABSTRACT
When deciding between different options, individuals are guided by the expected (mean) value of the different outcomes and by the associated degrees of uncertainty. We used functional magnetic resonance imaging to identify brain activations coding the key decision parameters of expected value (magnitude and probability) separately from uncertainty (statistical variance) of monetary rewards. Participants discriminated behaviorally between stimuli associated with different expected values and uncertainty. Stimuli associated with higher expected values elicited monotonically increasing activations in distinct regions of the striatum, irrespective of different combinations of magnitude and probability. Stimuli associated with higher uncertainty (variance) elicited increasing activations in the lateral orbitofrontal cortex. Uncertainty-related activations covaried with individual risk aversion in lateral orbitofrontal regions and risk-seeking in more medial areas. Furthermore, activations in expected value-coding regions in prefrontal cortex covaried differentially with uncertainty depending on risk attitudes of individual participants, suggesting that separate prefrontal regions are involved in risk aversion and seeking. These data demonstrate the distinct coding in key reward structures of the two basic and crucial decision parameters, expected value, and uncertainty.

Show MeSH
Related in: MedlinePlus