Reasoning about others’ thoughts and intentions, known as “theory of mind,” is a key aspect of social cognition. This ability depends on specific brain regions, particularly association areas, which have evolved significantly in humans compared to other species.
A recent study by Northwestern Medicine explored how humans evolved to excel at understanding the thoughts and intentions of others. The findings could offer insights into the development of this ability and may have potential implications for treating psychiatric conditions like anxiety and depression.
Senior author Rodrigo Braga said, “We spend a lot of time wondering, ‘What is that person feeling, thinking? Did I say something to upset them? The parts of the brain that allow us to do this are in regions of the human brain that have expanded recently in our evolution, implying that it’s a recently developed process. In essence, you’re putting yourself in someone else’s mind and making inferences about what that person thinks when you cannot know.”
The study found that the more recently evolved areas of the human brain involved in social interactions, known as the social cognitive network, constantly communicate with the amygdala, an ancient brain region typically associated with detecting threats and processing fear.
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While the amygdala is often linked to fear responses—such as the physical and emotional reactions to seeing a snake—it also plays other roles, including involvement in social cognition.
Braga said, “For instance, the amygdala is responsible for social behaviors like parenting, mating, aggression, and the navigation of social-dominance hierarchies. Previous studies have found co-activation of the amygdala and social cognitive network, but our study is novel because it shows that communication is always happening.”
The study revealed that a specific part of the amygdala, the medial nucleus, plays a crucial role in social behaviors. This research is the first to show that the medial nucleus is connected to the newly evolved regions of the social cognitive network, which are responsible for understanding others’ thoughts and intentions. This connection allows the social cognitive network to incorporate the amygdala’s processing of emotionally significant information.
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The discovery was made possible through functional magnetic resonance imaging (fMRI), which detects brain activity by measuring changes in blood oxygen levels.
Using high-resolution fMRI data from six participants, provided by collaborator Kendrick Kay at the University of Minnesota, the researchers could observe details of the social cognitive network that were previously undetectable with lower-resolution scans. Additionally, the findings were replicated in each participant, enhancing the robustness of the results.
Edmonds, a neuroscience Ph.D. candidate in Braga’s lab at Northwestern, said, “One of the most exciting things is we were able to identify network regions we weren’t able to see before. That’s something that had been underappreciated before our study, and we could get at that because we had such high-resolution data.”
Authors noted, “Both anxiety and depression involve amygdala hyperactivity, which can contribute to excessive emotional responses and impaired emotional regulation. Currently, someone with either condition could receive deep brain stimulation for treatment. Still, since the amygdala is located deep within the brain, directly behind the eyes, it means having an invasive, surgical procedure.”
“Now, with this study’s findings, a much less-invasive procedure, transcranial magnetic stimulation (TMS), might be able to use knowledge about this brain connection to improve treatment.”
“Through this knowledge that the amygdala is connected to other brain regions — potentially some that are closer to the skull, which is an easier region to target — that means people who do TMS could target the amygdala instead by targeting these other regions.”
Journal Reference:
- Donnisa Edmpnds, Joseph Salvo et al. The human social cognitive network contains multiple regions within the amygdala. Science Advances. DOI: 10.1126/sciadv.adp0453