Selective deficit in personal moral judgment following damage to ventromedial prefrontal cortex

Abstract

Recent fMRI evidence has detected increased medial prefrontal activation during contemplation of personal moral dilemmas compared to impersonal ones, which suggests that this cortical region plays a role in personal moral judgment. However, functional imaging results cannot definitively establish that a brain area is necessary for a particular cognitive process. This requires evidence from lesion techniques, such as studies of human patients with focal brain damage. Here, we tested 7 patients with lesions in the ventromedial prefrontal cortex and 12 healthy individuals in personal moral dilemmas, impersonal moral dilemmas and non-moral dilemmas. Compared to normal controls, patients were more willing to judge personal moral violations as acceptable behaviors in personal moral dilemmas, and they did so more quickly. In contrast, their performance in impersonal and non-moral dilemmas was comparable to that of controls. These results indicate that the ventromedial prefrontal cortex is necessary to oppose personal moral violations, possibly by mediating anticipatory, self-focused, emotional reactions that may exert strong influence on moral choice and behavior.

Figures

Fig. 1

Location and degree of overlap of brain lesions. The figure shows the lesions of the seven ventromedial prefrontal patients. Lesions are projected on the same five axial templates following the method developed by Damasio and Damasio (1989). The level of the axial slices has been marked by black lines on the mesial view of a right hemisphere drawing. Progressively darker shades denote the degree to which lesions involve the same brain regions, as indicated in the legend.

Fig. 2

Response time for ‘appropriate’ and ‘inappropriate’ responses to personal and impersonal moral dilemmas in patients and controls. Bars refer to 1 standard error of the mean.

Fig. 3

Proportion of ‘appropriate’ responses to personal and impersonal moral dilemmas in patients and controls. Bars refer to 1 standard error of the mean.