Fight or flight: Serotonin neurons prompt brain to make the right call

January 31, 2019

Known for its role in relieving depression, the neurochemical serotonin may also help the brain execute instantaneous, appropriate behaviors in emergency situations, according to a new Cornell study published Feb. 1 in Science.

The researchers studied brain activity patterns in mice. If a mouse was experiencing a threat, dorsal raphe serotonin neurons would fire during movements. But, when there was a calm, positive environment, these serotonin neurons would fire during pauses in active behavior.

"This switch really surprised us," said senior author Melissa Warden, assistant professor and the Miriam M. Salpeter Fellow in the Department of Neurobiology and Behavior. "It was our first clue that something really strange might be going on in the brain in emergency situations."

In emergency fight-or-flight situations, behavioral choices are different from the decisions an animal might make in less-critical situations. For example, if a mouse sits in the middle of an exposed field and a hawk spies it for food, the mouse may see the hawk start to swoop in and the mouse's survival instinct tells it to run. The escape response is appropriate, Warden said.

"But if the hawk is flying overhead and it hasn't seen the mouse, but the mouse has seen the hawk, it is appropriate for the mouse to freeze in place to avoid being detected," she said. "In this situation, freezing in place is a better decision than attempting to flee, because the odds of survival are higher."

In high-threat situations, stimulating serotonin neurons elicits escape attempts. In lower threat environments, stimulating these neurons causes pausing.

Thus, stimulating serotonin neurons is probably promoting the context-appropriate response. "It may cause animals to react to their environment, to do what's appropriate in light of the current situation," Warden said.

Like a global command center, serotonin sends signals all over the brain, she said. Fully understanding how this system prompts different behaviors in different environments may shed light on the role of other systems in the brain.

Said Warden: "Considering the widespread distribution of serotonin neurons throughout the brain, this finding raises the possibility that the 'emergency brain' operates in a fundamentally different way."

Co-lead authors Changwoo Seo and Akash Guru are both doctoral candidates in the field of neurobiology and behavior. In addition to Warden, Seo and Guru, the research, "Intense Threat Switches Dorsal Raphe Serotonin Neurons to a Paradoxical Operational Mode," was co-authored by postdoctoral researcher Brianna J. Sleezer; doctoral candidate Yi-Yun Ho, M.Eng '13; graduate student Brendan Ito; Christina Boada '15, Michelle Jin '17, Nicholas A. Krupa '18, Durga Kullakanda '19 and Cynthia X. Shen '20; and Elias Wang '16, a doctoral candidate at Stanford.
-end-
The research was funded by a Director's New Innovator Award from the National Institutes of Health, the New York Stem Cell Foundation, the Alfred P. Sloan Foundation, the Whitehall Foundation, the Brain and Behavior Research Foundation, the Mong Family Foundation, and Cornell. Warden is a New York Stem Cell Foundation-Robertson Neuroscience Investigator.

Cornell University

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.