Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Feb 15;6:20982.
doi: 10.1038/srep20982.

Representation of Economic Preferences in the Structure and Function of the Amygdala and Prefrontal Cortex

Affiliations
Free PMC article

Representation of Economic Preferences in the Structure and Function of the Amygdala and Prefrontal Cortex

Alan S R Fermin et al. Sci Rep. .
Free PMC article

Abstract

Social value orientations (SVOs) are economic preferences for the distribution of resources - prosocial individuals are more cooperative and egalitarian than are proselfs. Despite the social and economic implications of SVOs, no systematic studies have examined their neural correlates. We investigated the amygdala and dorsolateral prefrontal cortex (DLPFC) structures and functions in prosocials and proselfs by functional magnetic resonance imaging and evaluated cooperative behavior in the Prisoner's Dilemma game. We found for the first time that amygdala volume was larger in prosocials and positively correlated with cooperation, while DLPFC volume was larger in proselfs and negatively correlated with cooperation. Proselfs' decisions were marked by strong DLPFC and weak amygdala activity, and prosocials' decisions were marked by strong amygdala activity, with the DLPFC signal increasing only in defection. Our findings suggest that proselfs' decisions are controlled by DLPFC-mediated deliberative processes, while prosocials' decisions are initially guided by automatic amygdala processes.

Figures

Figure 1
Figure 1. Experimental design and task diagram.
(a) Stake size used in the sequential one-shot Prisoner’s Dilemma game and reconstructed payoff matrices. The payoff matrices themselves were not shown to subjects. (b) Player 2 preprogrammed the conditional choice probability based on the preceding choice of Player 1. (c) Task events. Following the inter-trial interval (ITI), each trial started with the random selection of an anonymous partner for the role of Player 2. The subject inside the fMRI scanner played the role of Player 1 and was the first to make a choice. Following the indication of whose turn it was to make a choice, a pseudo-randomly chosen stake size was displayed for 4–6 s. The subject was allowed to make a button press only during the response period (~12 s) indicated by a go signal (circle displayed around the buttons). A choice made within the response period highlighted the chosen button, while failing to make a choice displayed a failure message, although subjects were still requested to press a button. Player 1’s choice was observed and followed by the choice of Player 2. Both players had the choice to either Provide (G, cooperate) and transfer to the partner the whole stake, which was doubled in value, or Not Provide (N, defect) and keep the original stake value. Feedback, displayed at the end of every trial, showed the earned payoff by each player.
Figure 2
Figure 2. Choice behavior in the Prisoner’s Dilemma game.
(a) The overall cooperation rate of prosocials was significantly higher compared to that of proselfs (F(1,32) = 47.19, P < 0.0001). (b) Prosocials’ cooperation rate was also higher for each stake size. The main effect of stake size was significant (F(2,64) = 63.35, P < 0.0001), indicating that cooperation rate decreased as the stake size increased. The social value orientation × stake size interaction was not significant (F(2,64) = 1.65, P = 0.200), suggesting that prosocials’ cooperation was consistently higher than that of proselfs was, regardless of stake size.
Figure 3
Figure 3. Correlation between amygdala and dorsolateral prefrontal cortex (DLPFC) gray matter volumes with social value orientation (SVO) and cooperative behavior in the Prisoner’s Dilemma game.
(a) Left amygdala volume was significantly larger in prosocials than it was in proselfs (positive correlation with SVO, 66 voxels, x = −17, y = −9, z = −12, t = 2.61, P < 0.05 family-wise error (FWE) corrected) and (b,c) positively correlated with cooperation rate (81 voxels, x = −24, y = 0, z = −21, t = 2.57, P < 0.05 FWE corrected). (d) Right DLPFC volume was significantly larger in proselfs than it was in prosocials (negative correlation with SVO, 118 voxels, x = 29, y = 41, z = 30, t = 3.28, P < 0.05 FWE corrected), and (e,f) negatively correlated with cooperation rate (65 voxels, x = −30, y = 48, z = 33, t = 2.77, P < 0.05 FWE corrected). In (c,f), the regression line was computed for the whole sample; the red and blue dots represent individual data points of prosocials and proselfs, respectively. For visualization purposes, panels (a–d) and the voxel clusters are displayed at P < 0.001, uncorrected.
Figure 4
Figure 4. Activity signals (represented as beta weights) in the dorsolateral prefrontal cortex (DLPFC) and amygdala distinguish between prosocials and proselfs.
(a) Overall signal intensity (beta estimates) in the DLPFC and amygdala during the delay period. (b) Signal intensity in the delay period separated by social value orientation and choice type. The stars on top of each bar set represent statistically significant differences. For (a), significant differences are between prosocials and proselfs in the amygdala (*** = P < 0.0001). For (b), significant differences are between choice types by prosocials in the DLPFC (* = P < 0.05). The beta parameters were estimated using the voxel clusters identified in the VBM analysis shown in Fig. 2.
Figure 5
Figure 5. Time course of neural activity in the right dorsolateral prefrontal cortex (DLPFC) and left amygdala.
(a) An early increase in signal was observed in the right DLPFC of proselfs when choosing to either cooperate or defect; in contrast, only a late signal increase was observed in prosocials for defection choices. (b) An early signal increase was observed in the left amygdala during both cooperative and defection choices by prosocials. No significant signal increase in the left amygdala was observed in proselfs, regardless of choice type. See the Methods section for more details regarding analysis.

Similar articles

See all similar articles

Cited by 7 articles

See all "Cited by" articles

References

    1. Messick D. M. & McClintock C. G. Motivational basis for choice in experimental games. J. Exp. Soc. Psychol. 4, 1–25 (1968).
    1. Van Lange P. A. M. The pursuit of joint outcomes and equality in outcomes: an integrative model of social value orientation. J. Pers. Soc. Psychol. 77, 337–349 (1999).
    1. Balliet D., Parks C. & Joireman J. Social value orientation and cooperation in social dilemmas: a meta-analysis. Group Process Intergroup Relat. 12, 533–547 (2009).
    1. Liebrand W. B. G., Wilke H. A. M., Vogel R. & Wolters F. J. M. Value orientation and conformity in three types of social dilemma games. J. Conflict Resolut. 30, 77–97 (1986).
    1. Liebrand W. B. G. & McClintock C. G. The ring measure of social values: a computerized procedure for assessing individual differences in information processing and social value orientation. Eur. J. Pers. 2, 217–230 (1988).
Feedback