Summary: A new study has identified a brain circuit that responds quickly and uniformly to threats in animals, a phenomenon observed in schools of fish and herds of mammals.
The study focuses on synchronized immobilized mice and paves the way for improved understanding of social interactions in neuropsychiatric disorders in general. Rats were trained to associate an auditory signal with perceived threat, demonstrating critical connections between two brain regions—the ventral hippocampus and the basolateral amygdala—coordinating the threat response.
This finding may provide a basis for further research on brain connectivity in more complex social situations and potential therapeutic targets.
Key facts:
- A specialized brain circuit has been identified that provides a rapid, coordinated response to threats in animals.
- This discovery was made by studying the relationship between the ventral hippocampus and the basolateral amygdala by studying synchronized immobilized pairs of rats.
- The study provides a basis for advancing research on social communication and developing targeted treatments for neuropsychiatric disorders.
Source: Virginia Tech
Individual fish in schools tend to disperse together when a predator is between them.
Similar examples of well-coordinated group movements and failure to move when threatened have long been observed in insects and mammals.
Now, for the first time, a brain pathway has been discovered that allows individual animals to quickly coordinate a single response, without any practice.
Soon to be published in the print edition of the magazine Biological psychiatryVirginia Tech scientists with the Fralin Biomedical Research Institute describe how they studied synchronized immobility in VTC pairs of mice and identified the brain circuitry responsible for this behavior.
The study aims to advance research into the poorly understood brain activity underlying coordinated group activity and social interaction in general, which is implicated in a variety of human neuropsychiatric disorders such as attention deficit hyperactivity disorder (ADHD), autism, and others. Spectrum Disorders (ASD) and Social Communication Disorders (CD).
“There are many examples of coordinated defense responses in nature — bulls, for example, form a circle when faced with a threat,” said Alexey Morozov, assistant professor at Fralin Biomedical Research Institute and co-author of the study.
“Synchronization under threat is an evolutionarily conserved survival mechanism and occurs in all species, including humans. This type of behavior has not been measured in the laboratory before, but now we can explore the underlying mechanism by measuring this reaction quantitatively.
Rats are trained to associate hearing with threat, like a fire drill. The researchers studied the parts of the brain that remember fear and social information, and found that the special connection between the two parts of the brain, the ventral hippocampus and the basolateral amygdala, plays an important role in coordinating behavior when faced with a threat.
The data suggest a method for investigating these brain connections in more complex situations. Although the study began with individual pairs, more research is needed to determine whether the same pathway is responsible for coordinating larger group behaviors such as hugging in larger groups.
“This gives us a way to get a deeper understanding of social behavior,” Morozov said. “At home and at work, people coordinate and exchange information with partners. We now have a model that helps us understand the underlying brain pathways.”
“This is one of the most important discoveries in recent years in identifying the sites and underlying mechanisms that mediate important social interactions in the brain,” said Michael Friedlander, vice president and executive director of Health Sciences and Technology. Fralin Biomedical Research Institute.
“While these behavioral disorders 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 affected.
“Dr. Morozov and his team designed and implemented an elegant series of experiments in mice to provide a solid foundation for advancing this science and shortening the time to develop more systematic targeted therapies in humans.”
Research Assistant Professor Wataru Ito and Research Assistant Alexander Palmer, also of the Fralin Biomedical Research Institute’s Center for Neurobiology, participated in the research.
So neuroscience research news
Author: John Pastor
Source: Virginia Tech
Contact: John Pastor – Virginia Tech
Image: Image credited to Neuroscience News.
Preliminary study: Closed access.
“Social conditioning of conditioned fear in rats requires amygdala ventral hippocampus input.” by Alessi Morozov et al. Biological psychiatry
Draft
Social conditioning of conditioned fear in rats requires amygdala ventral hippocampus input.
Background
It characterizes social organisms as an evolutionarily-preserved means of development. Adaptation to risk specifically favors survival and occurs in all species, including humans, but the underlying mechanism is unknown due to the lack of relevant animal models. Here, we developed a rat paradigm in which rats mimic a classically conditioned fear response and identify the underlying neural circuitry.
Methods
Male and female rats were individually trained using auditory fear conditioning and tested 24 hours later as dice, allowing unrestricted social interaction while exposed to conditioning stimuli under visible or infrared illumination to avoid visual cues. Synchronization of static or freezing collisions was calculated using Cohen’s effect size. d For the difference between actual ice-time overlap and coincidental overlap.
Activation of the dorsomedial prefrontal cortex, dorsal hippocampus, or ventral hippocampus was achieved by local concentrations of musmol. Chemogenetic disruption of the hippocampus-amygdala pathway was performed by expressing hM4D (GI) in ventral hippocampal neurons and injecting clozapine. N– Oxidation in the amygdala.
Results
Rats have synchronous but not contextual fear. It was higher in men than in women and weakened in the absence of visible light. Constipation, however, inactivation of the dorsal hippocampus or dorsomedial prefrontal cortex prevented fear conditioning. Finally, disruption of the hippocampus-amygdala pathway reduced fear conditioning.
Conclusions
Rats synchronize fear expression dependent on the ventral hippocampus-amygdala pathway, suggesting that the hippocampus relays social information to the amygdala to synchronize the threat response.