Brain Injuries: The Reason For Increased Impulsivity And Social Influence

A new study has shown that an area of ​​the brain called the medial prefrontal cortex (mPFC) plays an important role in our decision-making and how we are influenced by others. Researchers have found that damage to one part of the mPFC (dmPFC) makes people more vulnerable to the opinions of others, while damage to another part (vmPFC) increases the tendency to seek immediate rewards. This helps to better understand how the brain controls choices and social influence in our daily lives.

Decision-making, whether in social or economic situations, is an essential part of our daily lives. Choices such as waiting for a greater reward in the future or giving in to the temptation of something immediate, or changing our opinions based on the opinions of others, are linked to specific areas of our brain.

One such region is the medial prefrontal cortex (mPFC), which has long been studied for its role in these processes. Research is trying to understand how different parts of the mPFC contribute to decisions that involve our own interests and interactions with others.

Furthermore, there is great scientific interest in discovering whether damage in this area actually affects our ability to resist the influence of others and our tendency to be more or less impulsive.

When damaged, the individual may start to act more impulsively, make risky decisions without thinking about the consequences, and have difficulty following social rules. In addition, the person may become more vulnerable to the influence of others, changing their choices just to align with what others think or want.

These changes show how the prefrontal cortex is essential for the balance between what we feel, think, and how we behave in society. Generally speaking, the mPFC can be divided into two main parts: the dorsal part (dmPFC), which is usually associated with thinking about others and social cognition, and the ventral part (vmPFC), which seems to be more involved in decisions related to the individual himself.

For a long time, these conclusions came from brain imaging studies, which show which areas are activated at certain times, but do not prove that these areas are essential for these behaviors. Therefore, scientists have sought clearer answers by studying people with brain injuries.

A new study involving a rare and large number of participants with lesions in the medial prefrontal cortex (33 people) compared how these lesions affect economic decisions and social influence. The researchers also looked at 17 people with lesions in other areas of the brain and 71 healthy individuals.

The participants took tests to measure whether they were more patient or impulsive in their choices and were then exposed to the economic preferences of two fictitious other people, one more impulsive and the other more patient.

The goal was to see to what extent people changed their own choices after learning about the preferences of others, an example of how we are influenced socially.

The results showed that damage to the dorsal prefrontal cortex made participants more vulnerable to social influence, especially when the other person was more impulsive. 

Lesions in the ventral prefrontal cortex were linked to a greater tendency to seek immediate rewards, i.e., more economic impulsivity. These findings provide clear evidence that different parts of the medial prefrontal cortex do indeed have distinct functions in how we make decisions and how we are influenced by others.

The research reinforces the importance of this area of ​​the brain in the processes that balance our own values ​​with the social pressures we face.

READ MORE:

Dorsomedial and ventromedial prefrontal cortex lesions differentially impact social influence and temporal discounting

Zhilin Su, Mona M. Garvert, Lei Zhang, Todd A. Vogel, Jo Cutler, Masud Husain, Sanjay G. Manohar, and Patricia L. Lockwood 

PLoS Biol 23(4): e3003079. April 28, 2025.

https://doi.org/10.1371/journal.pbio.3003079

Abstract:

The medial prefrontal cortex (mPFC) has long been associated with economic and social decision-making in neuroimaging studies. Several debates question whether different ventral mPFC (vmPFC) and dorsal mPFC (dmPFC) regions have specific functions or whether there is a gradient supporting social and nonsocial cognition. Here, we tested an unusually large sample of rare participants with focal damage to the mPFC (N = 33), individuals with lesions elsewhere (N = 17), and healthy controls (N = 71) (total N = 121). Participants completed a temporal discounting task to estimate their baseline discounting preferences before learning the preferences of two other people, one who was more temporally impulsive and one more patient. We used Bayesian computational models to estimate baseline discounting and susceptibility to social influence after learning others’ economic preferences. mPFC damage increased susceptibility to impulsive social influence compared to healthy controls and increased overall susceptibility to social influence compared to those with lesions elsewhere. Importantly, voxel-based lesion-symptom mapping (VLSM) of computational parameters showed that this heightened susceptibility to social influence was attributed specifically to damage to the dmPFC (area 9; permutation-based threshold-free cluster enhancement (TFCE) p < 0.025). In contrast, lesions in the vmPFC (areas 13 and 25) and ventral striatum were associated with a preference for seeking more immediate rewards (permutation-based TFCE p < 0.05). We show that the dmPFC is causally implicated in susceptibility to social influence, with distinct ventral portions of mPFC involved in temporal discounting. These findings provide causal evidence for sub-regions of the mPFC underpinning fundamental social and cognitive processes.