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Individual fish in schools scatter in unison when a predator is in their midst.

Similar examples of precisely coordinated group movements and immobility during threats have long been observed in insects and mammals.

Now, for the first time, a brain pathway has been discovered that enables individual animals to rapidly coordinate a unified response, with no rehearsal required.

Publishing recently in the print edition of the journal Biological Psychiatry, Virginia Tech scientists with the Fralin Biomedical Research Institute at VTC described how they studied synchronized immobility in pairs of mice and identified the underlying brain circuit responsible for this behavior.

The study provides an identified target to advance research on the poorly understood brain activity that underlies coordinated group movement and, more broadly, social communication in general, which is compromised in a variety of human neuropsychiatric conditions such as attention hyperactivity disorder (ADHD), autism spectrum disorders (ASD) and social communication disorder (SCD).

“Examples of coordinated defensive responses in nature are numerous — oxen, for example, form a circle when they face a threat,” said Alexei Morozov, assistant professor of the Fralin Biomedical Research Institute and corresponding author of the study. “Synchronization under threat is an evolutionary-conserved survival mechanism and occurs across species, including humans. This type of behavior has never been measured in a lab before, but now we can now quantify this response and explore the underlying mechanisms.”

Mice were trained to associate an auditory cue to a potential threat, like a fire drill. The researchers studied parts of the brain that process and remember fear and social information, and they found that a specific connection between two parts of the brain, the ventral hippocampus and basolateral amygdala, plays an important role in coordinating behavior when faced with a threat.

The information suggests a method to investigate these brain connections in more complicated situations. Although the study began with pairs of individuals, more research is needed to determine whether the same pathway is responsible for coordinating larger group behavior, such as huddling, in larger groups.

“This gives us a way toward a deeper understanding of social behavior,” Morozov said. “At home and at work, people coordinate and exchange information with partners. Now we have a model that helps us understand the underlying brain pathway.”

“This is among the most significant discoveries made in recent years on identifying the sites and the potential underlying mechanisms in the brain that mediate these types of important social interactions,” said Michael Friedlander, Virginia Tech vice president for health sciences and technology and executive director of the Fralin Biomedical Research Institute. “While the pathologies in these behaviors are well characterized in human clinical populations, attempts at effective therapies have been hampered by a lack of understanding of which brain circuits and biological processes are impacted. Dr. Morozov and his team have designed and implemented an elegant series of experiments in mice to provide a potentially powerful base from which to advance this science and hopefully shorten the time to develop more strategically targeted therapies for humans.”

Research assistant professor Wataru Ito and research assistant Alexander Palmer, also of the Fralin Biomedical Research Institute’s Center for Neurobiology Research, participated in the research study.

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