Neural and behavioral signature of human social perception

Abstract

Social behavior is extremely variable among individuals, and the neural basis of this variability is still poorly understood. In this study, we aimed to investigate the neural basis of interindividual variability in the first step of social behavior, that is, social perception. For that purpose, we first used eye-tracking to measure social perception during the passive visualization of socially relevant movie clips. Second, we correlated eye-tracking data with measures of rest cerebral blood flow (CBF) obtained using arterial spin-labeling (ASL) MRI, an index of local rest brain function. The results showed a large interindividual variability in the number of fixations to the eyes of characters during passive visualization of movie clips displaying social interactions. Moreover, individual patterns remained stable across time, suggesting an individual signature of social behavior. Whole-brain analyses showed significant positive correlation between the number of fixations to the eyes and rest CBF: individuals who looked more to the eyes were those with higher rest CBF levels within the right superior temporal regions. Our results indicate the existence of a neural and behavioral signature associated with the interindividual variability in social perception.

Figure 1

Example of eye-tracking stimuli set: a total of six clips of 10 sec each displaying social scenes with two characters engaged in peer-to-peer social interactions (Le Petit Nicolas) were selected and assembled together to create a final movie of 60 sec.

Figure 2

Individual plots of the number of fixations to the eyes over the seven visualizations from 14 young healthy volunteers participating in Study 1 (each color represents one participant). The plot shows great between-subject variability as well as stability in the individual gaze patterns across time.

Figure 3

Frequency histogram of the number of fixations to the eyes from the 33 healthy volunteers participating in Study 2. This confirms great between-subject variability in this behavior and its normal distribution.

Figure 4

(a) Results of whole brain correlation analysis between the number of fixations to the eyes, measured by eye-tracking, and rest CBF, measured by ASL-MRI, overlaid on the MNI-152 template average brain (for illustration purposes, p values were set to 0.001 uncorrected). The MNI coordinates of the two significant peaks at p < 0.05 Family Wise Error (FWE) corrected for multiple comparisons at both the voxel and cluster level: x = 51, y = −25, z = 22; T = 5.89; P_FWE = 0.009; k_E = 48, P_FWE = 0.008 and x = 58, y = −30, z = −9; T = 5.47; P_FWE = 0.024; k_E = 3, P_FWE = 0.038. The color bar represents T-scores. (b) Plot of the correlation between the number of fixations to the eyes and the individual rest CBF values.