Nat Neurosci | Hong Weizhe's team reveals the neural mechanism of social behavior reward

Editor-in-Chief | How the neural network in the brain encodes and regulates the social behavior of animals has always been one of the important research areas of brain science.

Social behavior is one of the most complex behaviors that social animals (including humans) can show, and it is essential to animal survival and health.

In social behavior, the brain must make correct behavior judgments by processing social and non-social information.

Among social animals, including humans, participating in social behaviors is rewarding (Social Reward).

This abnormal processing of reward information is a prominent feature of many mental illnesses such as autism, depression, and schizophrenia.

However, we still know very little about how the brain controls the rewards of social behavior.

On April 5, 2021, the research team of Professor Weizhe Hong () at the University of California, Los Angeles (UCLA) (the first author is Dr.
Hu Rongfeng) published an an amygdala-to-hypothalamus circuit for social reward in Nature Neuroscience.
The latest research result [1], this is another important discovery made by Dr.
Hu Rongfeng after the medial amygdala (Medial Amygdala) of the brain is involved in the regulation of animal feeding behavior [2] published in Cell in February 2019.

The previous neural circuit research on social reward behavior mainly focused on the classic reward system in the brain.

The brain areas of these studies are concentrated in the ventral tegmental area (VTA), the nucleus accumbens area (NAc), and the brain areas connected to them [3-4].

The formation of social reward behavior requires identification and integration of social information.

Therefore, the regulation of social rewards may require the participation of neural circuits other than the classical reward circuits.

However, we don't know much about how other neural circuits mediate social rewards.

In order to better study the neural mechanisms of social rewards, the authors used an automated system to quantitatively measure the size of social rewards in mice (Figure 1).

The authors found that both female and male adult mice have the ability to receive social rewards.

Figure 1 An automated operant system for measuring social reward.
Through the comprehensive use of optogenetics, optical fiber recording and other technologies, the authors have discovered a novel neural loop that controls social reward behavior.

The middle amygdala (Medial Amygdala, MeA) is an important brain area downstream of the olfactory bulb system that mediates social behaviors.

Specific removal or ablation of GABAergic neurons in the central amygdala significantly reduces the social reward behavior of mice, and activating these neurons can produce a very strong reward effect.

Through the forward tracing technique, the author discovered that the central preoptic area (MPOA) is one of the most important projection areas of MeA.

Through optogenetic experiments, the author further confirmed that the neural circuit from MeA to MPOA is necessary to mediate social reward behavior.

Dopamine release is an important feature of reward behavior.

The author tried to record the release of dopamine in NAc while activating MeA neurons.

It was found that the activation of MeA neurons can lead to a significant increase in the release of dopamine in NAc (Figure 2).

This experiment further shows that MeA may be an important upstream brain area of ​​the classic reward loop.

Figure 2 Activating MeApd Vgat+ neurons triggers dopamine release in the NAc.
It is well known that positive social behaviors can reduce or alleviate disgust or anxiety.

However, the neural mechanism behind this phenomenon is largely unclear at present.

The authors found that the rewards generated by activating the MeA or MeA-to-MPOA loop can effectively help animals overcome their inherent aversion or avoidance behavior.

In summary, the researchers optimized an automated system to quantitatively measure the size of social rewards in mice, and for the first time discovered and confirmed the key role of the MeA-to-MPOA pathway in regulating social reward behavior.

This research promotes our understanding of the neural network coding and regulation of social behavior in the brain, and provides new ideas for the neural mechanisms of mental illnesses such as anxiety, autism, and depression.

Attached part of the recent work of Hong Weizhe’s team: 1.
Cell | Neural activities synchronized between different brains in social behavior 2.
Neuron | Hong Weizhe’s team reveals how the neural network in the brain recognizes and encodes gender.
Original link: https://doi.
org/10.
1038 /s41593-021-00828-2 Platemaker: Eleven References 1.
Hu RK, Zuo Y, Ly T, Wang J, Meera P, Wu YE, and Hong, W.
2021.
An amygdala-to-hypothalamus circuit for social reward.
Nature Neuroscience.
https://doi.
org/10.
1038/s41593-021-00828-2.
2.
Chen PB*, Hu RK*, Wu YE*, Pan L, Huang S, Micevych PE, Hong W.
2019.
Sexually dimorphic control of parenting behavior by the medial amygdala.
Cell 176, 1206–1221.
3.
Dölen G, Darvishzadeh A, Huang KW, Malenka RC.
2013.
Social reward requires coordinated activity of nucleus accumbens oxytocin and serotonin.
Nature 501, 179.
4.
Hung L, et al.
2017.
Gating of social reward by oxytocin in the ventral tegmental area.
Science 357, 1406–1411.
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