We’ve all been there. Moments after leaving a party, your brain is suddenly filled with intrusive thoughts about what others were thinking. “Did they think I talked too much?” “Did my joke offend you?” “Were they having a good time?”
In a new Northwestern Medicine study, scientists sought to better understand how humans evolved to become so adept at thinking about what’s going on in other people’s minds. The findings could have implications for one day treating psychiatric conditions such as anxiety and depression.
“We spend a lot of time asking ourselves, ‘What is that person feeling or thinking? Did I say something to upset them?'” said lead 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 is a recently developed process. In essence, you are putting yourself in the mind of another person and making inferences. about what that person is thinking when you really can’t know.”
The study found that the most recently evolved and advanced parts of the human brain that support social interactions, called the social cognitive network, are connected and in constant communication with an ancient part of the brain called the amygdala.
The amygdala, often called our “lizard brain,” is generally associated with threat detection and fear processing. A classic example of the amygdala in action is someone’s physiological and emotional response to seeing a snake: body startled, heart racing, palms sweaty. But the amygdala also does other things, Braga said.
“For example, the amygdala is responsible for social behaviors such as parenting, mating, aggression, and navigating social dominance hierarchies,” said Braga, an assistant professor of neurology at Northwestern University Feinberg School of Medicine. . “Previous studies have found coactivation of the amygdala and the social cognitive network, but our study is novel because it shows that communication always occurs.”
The study was published on November 22 in the journal Scientific advances.
High-resolution brain scans were key
Within the amygdala there is a specific part called the medial nucleus that is very important for social behaviors. This study was the first to show that the medial nucleus of the amygdala is connected to newly evolved social cognitive network regions, which are involved in thinking about other people. This link to the amygdala helps shape the function of the social cognitive network by giving access to the amygdala’s role in processing emotionally important content.
This was only possible thanks to functional magnetic resonance imaging (fMRI), a non-invasive brain imaging technique that measures brain activity by detecting changes in blood oxygen levels. University of Minnesota collaborator and study co-author Kendrick Kay provided Braga and co-author Donnisa Edmonds with fMRI data from the brains of six study participants, as part of the Natural Scenes Dataset (NSD). These high-resolution scans allowed scientists to see details of the social cognitive network that had never been detected in lower-resolution brain scans. What’s more, they were able to replicate the findings up to two times in each individual.
“One of the most interesting things is that we were able to identify regions of the network that we couldn’t see before,” said Edmonds, a neuroscience doctor. candidate in Braga’s lab at Northwestern. “That’s something that had been underestimated before our study, and we were able to get to that because we had very high-resolution data.”
Possible treatment of anxiety and depression.
Both anxiety and depression involve hyperactivity of the amygdala, which can contribute to excessive emotional responses and impaired emotional regulation, Edmonds said. Currently, someone with either condition could receive deep brain stimulation as a treatment, but since the amygdala is located deep in the brain, directly behind the eyes, it means undergoing an invasive surgical procedure. Now, with the findings of this study, a much less invasive procedure, transcranial magnetic stimulation (TMS), could use knowledge about this brain connection to improve treatment, the authors said.
“Through this knowledge that the amygdala is connected to other regions of the brain, potentially some that are closer to the skull, which is an easier region to target, that means that people doing TMS could target the amygdala in instead of targeting these other regions,” Edmonds said.
The study is titled “The human social cognitive network contains multiple regions within the amygdala.” Other Northwestern co-authors include Christina Zelano, Joseph J. Salvo, Nathan Anderson, Maya Lakshman and Qiaohan Yang.