(ORDO NEWS) — Previously, it was known that one of the nuclei of the hypothalamus is involved in the regulation of aggressive behavior, but it remained a mystery exactly which processes are involved in this.
Now American researchers have shown that the level of aggressive motivation is affected not by the activity of neurons in the zone, but by its fluctuations.
Aggression is inherent in most animal species. However, participation in a fight can be costly even for the winner.
Therefore, it is safer to start a conflict with threats and intimidation, and attack only when absolutely necessary.
This type of aggressive arousal has been observed in many organisms, but until now it was not known exactly how it is regulated by the brain.
To answer this question, American scientists used miniature micro endoscopes placed on the heads of mice.
So it was possible to track the activity of individual populations of neurons while the mice freely interacted with each other.
At the beginning of the last century, scientists found that electrical stimulation of deep areas of the brain can cause manifestations of rage.
Further studies have shown that the area of the brain responsible for aggression is the ventrolateral part of the ventromedial nucleus of the hypothalamus (VMHvl).
Stimulation of VMHvl induced mice to attack their relatives, while blocking it, on the contrary, stopped aggressive behavior without affecting other types of activity.
The scientists looked at the activity of several nuclei of the hypothalamus, including VMHvl, to find markers of attack decisions.
It turned out that the activity of VMHvl neurons only weakly correlated with when the mice behaved aggressively.
However, a small population of neurons remained constantly active during various contacts between rodents and relatives.
When fluctuations in its activity were weak, the mice explored or ignored each other; however, with an increase in this amplitude, aggression also intensified: the animals began to assume threatening postures and demonstrate dominant behavior.
When the strength of the oscillations reached a certain threshold value, they went on the attack.
According to scientists, this signal reflects the level of aggressive motivation of the animal. At the same time, the nucleus of the hypothalamus does not act as a “switch” for aggressive behavior, but as a kind of “volume control”.
The authors of the study also note that in mice that rarely fought, fluctuations in the activity of VMHvl neurons quickly returned to normal, while in active “fighters”, on the contrary, they grew rapidly and remained high for a long time.
Therefore, such a pattern is likely to be regulated by memories of past defeats or the degree of danger of the situation.
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