Cells associated with bravery identified in the hippocampus

Why do some people walk comfortably between skyscrapers on a Niagara raft or fearless rafts in a wooden barrel, while others freeze at the mere thought of climbing escalators in a mall? In a new study, scientists have discovered that a certain type of hippocampus cell plays a key role.

People differ when it comes to trying dangerous or exhilarating activities. Even siblings can show dramatic differences in risky behavior. The neural mechanisms underlying risk behaviors are largely unknown. However, scientists from the Department of Neuroscience of the University of Uppsala in Sweden and the Brain Institute of the Federal University of Rio Grande do Norte in Brazil have discovered that some cells of The hippocampus play a key role in risk behaviors and anxiety.

In an article published in the journal Nature CommunicationsThe authors show that neurons, called stimulated OLM cells, produce a cerebral rhythm present when animals feel safe in a threatening environment (for example, when they hide from a predator but are aware of the proximity of the predator). The study, produced by Drs. Sanja Mikulovic, Ernesto Restrepo, Klas Kullander and Richardson Leao, among others, have shown that manipulating OLM cells can control anxiety and risky behavior. Finding a way to quickly and robustly modulate risky behaviors is very important for the treatment of pathological anxiety, as the reduction of risky behavior is a hallmark in people with anxiety levels. high.

Adaptive anxiety (or normal) is essential for survival because it protects us from harm. Unfortunately, in a large number of people, anxiety can be dysfunctional and seriously affect daily life. In these cases, doctors often rely on antidepressants to help patients recover from the dysfunctional condition. However, these drugs work throughout the brain and not just in the areas where they are needed and can therefore cause serious side effects. Thus, drugs that affect a single region of the brain or a very specific group of cells can be a major advance in the treatment of anxiety and related disorders such as depression. Another interesting discovery in the study is that OLM cells can be controlled by pharmacological agents. In the past, the same group of scientists discovered that OLM cells were the guardians of memories in the hippocampus and that these cells were very sensitive to nicotine.

"This discovery may explain why people smoke when they are anxious," says Dr. Richardson Leao, a researcher at the Brain Institute of the Federal University of Rio Grande do Norte.

The involvement of the hippocampus in emotions is much less studied than its role in memory and cognition. In 2014, for example, the Nobel Prize was awarded for the discovery of "cells of the place" that represent a biological GPS and that underlie the memories of where we are located in our environment. Over the past decade, scientists have also begun to appreciate the role of the hippocampus in regulating emotions.

"It is fascinating to see how different regions of a single brain structure control distinct behaviors and interact with each other." Identifying specific circuits that underlie cognitive or emotional processes is crucial to disorders " says Dr. Sanja Mikulovic, University of Uppsala.

The discovery of these neurons and their role in anxiety and risk taking could pave the way for the development of highly effective anxiolytics and antidepressants without common side effects, such as apathy .

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More information:
Sanja Mikulovic et al, the OLM cells of the ventral hippocampus control the theta oscillations of type 2 and the response to predator odor, Nature Communications (2018). DOI: 10.1038 / s41467-018-05907-w