Sex-related functional asymmetry of the ventromedial prefrontal cortex in regard to decision-making under risk and ambiguity

Abstract

Previous work has provided preliminary indication of sex-related functional asymmetry of the ventromedial prefrontal cortex (vmPFC) in social and emotional functions and complex decision-making. Findings have been inconsistent, and based on small numbers of patients. Given the rarity of these neurological cases, replicable results across studies are important to build evidence for sex-related functional asymmetry of the vmPFC. Here we used a sample of sixteen neurological patients with unilateral damage to the left or right vmPFC and examined differences between men and women on a task that probed decision-making under risk or decision-making under ambiguity. We found that men with right-hemisphere vmPFC damage and women with left-hemisphere vmPFC damage demonstrated significantly reduced aversion to risk and ambiguity. Men with damage to the left vmPFC and women with damage to the right vmPFC showed aversion to risk and ambiguity comparable to participants with left or right-sided brain damage outside the vmPFC, and to comparison participants without brain damage. Our results add to previous findings of sex-related functional asymmetry of the vmPFC in decision-making. Our study also replicates findings of no observable behavioral differences between men and women without neurological damage on tests of decision-making. This pattern of neurobiological divergence but behavioral convergence between men and women may reflect a complex interplay of neuroendocrine, developmental, and psychosocial factors.

Keywords: Decision-making; Prefrontal cortex; Sex differences.

Figure 1. Lesion overlap maps (2 column figure)

Lesion overlap maps for (A) men and (B) women participants with vmPFC damage and (C) men and (D) women brain damaged comparison (BDC) participants. Right-sided lesion overlap is displayed in red, left-sided lesion overlap in blue. Green reflects interhemispheric overlap. Maximum lesion overlap for left- and right-sided cases in each group is displayed on scale bar.

Figure 2. Card Deck performance (1 column figure)

(A) Risk aversion, and (B) ambiguity aversion for each group in the Card Deck condition. Risk and ambiguity aversion reflect the proportion of trials where the sure option was chosen over the gamble. Error bars indicate standard error of the mean.

Figure 3. Knowledge Deck performance (1 column figure)

Risk aversion for each group in the Knowledge Deck condition. Risk aversion reflects the proportion of trials where the sure option was chosen over the gamble. Error bars indicate standard error for the mean of each group. There were no significant differences between groups in the Knowledge Condition for ambiguity aversion or expected value preference.