The neural bases for devaluing radical political statements revealed by penetrating traumatic brain injury

Abstract

Given the determinant role of ventromedial prefrontal cortex (vmPFC) in valuation, we examined whether vmPFC lesions also modulate how people scale political beliefs. Patients with penetrating traumatic brain injury (pTBI; N = 102) and healthy controls (HCs; N = 31) were tested on the political belief task, where they rated 75 statements expressing political opinions concerned with welfare, economy, political involvement, civil rights, war and security. Each statement was rated for level of agreement and scaled along three dimensions: radicalism, individualism and conservatism. Voxel-based lesion-symptom mapping (VLSM) analysis showed that diminished scores for the radicalism dimension (i.e. statements were rated as less radical than the norms) were associated with lesions in bilateral vmPFC. After dividing the pTBI patients into three groups, according to lesion location (i.e. vmPFC, dorsolateral prefrontal cortex [dlPFC] and parietal cortex), we found that the vmPFC, but not the dlPFC, group had reduced radicalism scores compared with parietal and HC groups. These findings highlight the crucial role of the vmPFC in appropriately valuing political behaviors and may explain certain inappropriate social judgments observed in patients with vmPFC lesions.

Keywords: political beliefs; radicalism; traumatic brain injury; ventromedial prefrontal cortex; voxel-based lesion-symptom mapping.

Fig. 1

Map shows the overlap density of the lesions in pTBI patients. Color depicts the number of patients with the overlapping lesion at each voxel. Orange indicates more subjects and blue indicates fewer subjects. The right hemisphere is shown on the reader’s left side

Fig. 2

VLSM of judgments about radicalism in the political belief task. VLSM analysis compares voxel by voxel the average score in the radicalism dimension in pTBI patients vs controls. Colored areas indicate a significant association between presence of lesion in that location and lower radicalism score. Color bar indicates z-scores; yellow indicates areas with the highest z-score

Fig. 3

Map shows the overlap of the lesions in the (A) vmPFC, (B) dlPFC and (C) parietal pTBI group. The maximum overlay is 10, 6 and 6 subjects for the vmPFC, dlPFC and parietal group, respectively. Right hemisphere is shown on the left side

Fig. 4

Radicalism ratings on statements grouped by different degrees of radicalism for the four groups: vmPFC, dlPFC, parietal and controls. The vmPFC group judged the middle and high radical statements as significantly more moderated compared with the parietal and HC groups (P values < 0.005). The dashed line indicates a neutral rating (i.e. neither moderate nor radical)