"We spend a lot of time wondering, 'What is that person feeling, thinking? Did I say something to upset them?'" said senior author Rodrigo Braga. "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, and that implies 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 is thinking when you cannot really know."
The study highlights a constant interaction between the amygdala, an ancient part of the brain associated with emotional processing, and the recently evolved social cognitive network, which supports complex social reasoning. This connection may explain how humans navigate social interactions and relationships.
The "lizard brain" at work
Often called the "lizard brain," the amygdala is typically known for triggering fear and threat responses, such as a racing heart or sweaty palms when encountering a snake. However, Braga pointed out that the amygdala also governs critical social behaviors like parenting, mating, and navigating dominance hierarchies.
"For instance, the amygdala is responsible for social behaviors like parenting, mating, aggression, and the navigation of social-dominance hierarchies," said Braga, an assistant professor of neurology at Northwestern University Feinberg School of Medicine. "Previous studies have found co-activation of the amygdala and social cognitive network, but our study is novel because it shows the communication is always happening."
The research, published on Nov. 22 in 'Science Advances', marks the first time scientists have mapped the specific links between the amygdala's medial nucleus - a region crucial for social behaviors - and the social cognitive network. This connection allows the social cognitive network to access emotional information processed by the amygdala.
High-resolution imaging reveals new details
The study used functional magnetic resonance imaging (fMRI) to map this brain interaction. High-resolution data provided through the Natural Scenes Dataset (NSD), collected by collaborator Kendrick Kay at the University of Minnesota, allowed researchers to observe previously undetected details within the social cognitive network.
"One of the most exciting things is we were able to identify network regions we weren't able to see before," said co-author Donnisa Edmonds, a neuroscience Ph.D. candidate in Braga's lab. "That's something that had been underappreciated before our study, and we were able to get at that because we had such high-resolution data."
The findings were replicated across individual participants multiple times, underscoring the reliability of the results.
Implications for treating anxiety and depression
The study's insights into the brain's connectivity could help refine treatments for conditions like anxiety and depression, which involve heightened amygdala activity. Traditional treatments like deep brain stimulation require invasive procedures, as the amygdala is located deep within the brain. However, this study suggests a less-invasive approach could be possible.
"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," Edmonds said.
This approach could make transcranial magnetic stimulation (TMS) a more effective and less-invasive option for managing emotional regulation issues tied to anxiety and depression.
Research Report:The study offers valuable insights into the human brain's evolution and its role in shaping our social and emotional experiences.
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