The role of ventral medial prefrontal cortex in social decisions: converging evidence from fMRI and frontotemporal lobar degeneration

Abstract

The ventral medial prefrontal cortex (vmPFC) has been implicated in social and affectively influenced decision-making. Disease in this region may have clinical consequences for social judgments in patients with frontotemporal lobar degeneration (FTLD). To test this hypothesis, regional cortical activation was monitored with fMRI while healthy adults judged the acceptability of brief social scenarios such as cutting into a movie ticket line or going through a red light at 2 AM. The scenarios described: (i) a socially neutral condition, (ii) a variant of each scenario containing a negatively valenced feature, and (iii) a variant containing a positively valenced feature. Results revealed that healthy adults activated vmPFC during judgments of negatively valenced scenarios relative to positive scenarios and neutral scenarios. In a comparative behavioral study, the same social decision-making paradigm was administered to patients with a social disorder due to FTLD. Patients differed significantly from healthy controls, specifically showing less sensitivity to negatively valenced features. Comparative anatomical analysis revealed considerable overlap of vmPFC activation in healthy adults and vmPFC cortical atrophy in FTLD patients. These converging results support the role of vmPFC in social decision-making where potentially negative consequences must be considered.

FIGURE 1

MEAN (± SEM) PROFILE OF DECISION-MAKING BY HEALTHY YOUNG ADULTS DURING THE fMRI EXPERIMENT AND BY FTLD PATIENTS AND AGE-MATCHED OLDER CONTROLS IN THE BEHAVIORAL EXPERIMENT¹ NOTE 1. Graphed scores are differences for judgments of positively- and negatively-valenced scenarios relative to judgments of baseline scenarios in each individual. All judgments differ significantly from baseline except for FTLD patients’ judgments of scenarios with a negative social value. FTLD patients differed significantly from controls’ judgments only for negatively-biased scenarios. See text for details.

FIGURE 2

fMRI ACTIVATION FOR JUDGMENTS OF NEGATIVELY-VALENCED SCENARIOS RELATIVE TO POSITIVELY-VALENCED SCENARIOS

FIGURE 3

ANATOMICAL OVERLAP OF CORTICAL ATROPHY IN FTLD PATIENTS WITH SOCIAL DISORDER (SHOWN IN BLUE) WITH fMRI ACTIVATIONS IN HEALTHY ADULTS UNDERTAKING JUDGMENTS OF NEGATIVE SOCIAL SCENARIOS (SHOWN IN ORANGE).