From omega to Alpha

Optogenetic Goodwin for Cowardly Mice

Maxim Rousseau, Polit.roo

Wizard Goodwin's miraculous remedy was able to endow the Cowardly Lion with courage. Now scientists have achieved the same effect in reality, only not with a lion, but for now with mice. But if Goodwin, as it turned out later, used a placebo, then in the current experiment, the mouse brain was really affected. Optogenetics, a method of controlling nerve cells using a laser, has helped turn the most timid mice into alpha males capable of regularly winning the competition. To do this, it turned out to be sufficient to activate a certain chain of neurons in the anterior part of the frontal lobes of the brain.

Many social animals have a hierarchy that distinguishes dominant and one or more levels of subordinate individuals. In ethology, it is customary to designate the levels of such a hierarchy with Greek letters. Now neuroscientists have discovered a chain of neurons in the brains of mice, the activation of which turned the most timid and downtrodden rodents into bold and dominant. Professor Hailan Hu from Zhejiang University in Hangzhou, who led this work, says: "We stimulate a part of the brain and force mice to move up the social ladder."

Previous studies have shown that the dorsomedial prefrontal cortex of the brain is activated during social interactions, in particular, during decision-making about whether to be firm or submissive towards other individuals. Now it was possible to identify a specific neural circuit associated with dominance.

A study published by the journal Science (Zhou et al., History of winning remodels thalamo-PFC circuit to reinforce social dominance) used genetically modified mice whose target group of neurons was sensitive to light. With the help of an optical fiber passed into the brain, scientists could turn on and off the corresponding neural circuit at will.

For the experiment, male mice were selected, which occupied a subordinate position in their groups. After activating the corresponding neural circuit, they immediately became bold, persistent, easily entering into conflicts and most often prevailed over their relatives, forcing them to obey.

Several experiments were conducted to test the effect. In one, two males had to move towards each other through a narrow tube. They didn't have a chance to miss each other, so one of them had to step back when they met. Mice that usually found themselves in this role, after activating the neurons, began to gain the upper hand in 90% of cases. Before them retreated those relatives to whom they had previously lost. In another experiment, mice competed for a warm corner in a cage with a cold floor, and also stimulation of neurons helped them to emerge victorious.

It is especially interesting that after the termination of neuronal activation, not all experimental mice returned to their former subordinate rank. Some of them remained assertive and bold when their brains were no longer artificially controlled. Scientists have called this the "winner effect."

The authors note that similar schemes exist in the human brain. Although hierarchies in people's social structures are less rigid, similar mechanisms may manifest themselves in them. Therefore, the study may be important for working with psychiatric disorders, such as excessive desire for dominance or, conversely, a complete lack of motivation for social competition.

It is especially interesting that after the termination of neuronal activation, not all experimental mice returned to their former subordinate rank. Some of them remained assertive and bold when their brains were no longer artificially controlled. Scientists have called this the "winner effect."

The authors note that similar schemes are also present in the human brain. Although hierarchies in people's social structures are less rigid, similar mechanisms may manifest themselves in them. Therefore, the study may be important for working with psychiatric disorders, such as excessive desire for dominance or, conversely, a complete lack of motivation for social competition.

Optogenetic activation of neurons has been repeatedly used in experiments with mice. It allowed various researchers to erase the mice's memories or make them feel thirsty. In January of this year, using optogenetic stimulation, scientists turned ordinary laboratory mice into predators. Such an experiment was conducted at Yale University under the guidance of neuroscientist Ivan de Araujo. In his laboratory, the eating behavior of rodents is being investigated. One day, a scientist came across an article from 2005, the authors of which found that in rats, during hunting behavior, a section of the amygdala – one of the brain departments - is activated. Moreover, the "hunting center" was located in the department that is usually responsible for fear and anxiety. The researcher decided to check whether these data are also true for mice. He told about his experiment in the journal Cell.

Initially, Ivan de Araujo and his colleagues believed that mice would show only some elements of predator behavior, for example, they would chase crickets, which scientists offered them as possible prey, but they would not kill and eat them. But mice, after exposure to the necessary neurons, turned into full-fledged predators. They began to show behavior unusual for them before: chasing crickets, jumping on them, wrapping their paws around them, killing with a bite from above and eating.

Researchers have identified two neural pathways, one of which is responsible for chasing prey, and the other for the accuracy and strength of the bite. If the experimenters used a laser on only one group of neurons, the mice, for example, only chased crickets, but could not kill them. In the case of simulating both paths at the same time, the mice attacked not only the crickets, but also other objects in their cage: chips and bottle stoppers. However, the mice did not attack their relatives. According to the researchers, this is due to the fact that the activity of the amygdala in such cases is suppressed by other parts of the brain.

Portal "Eternal youth" http://vechnayamolodost.ru  14.07.2017