Science . . . Black matter: the common center of sleep and motor control.

In November, many animals remain motionless during sleep, and the decrease of EMG activity is one of the important criteria for identifying whether animals enter sleep state [1-4].the arousal state and the motor state of the animal brain influence each other.however, the coordination between brain state and motor activity and the specific coordination mechanism are not clear.on January 24, 2020, Yang Dan research group of the University of California, Berkeley, USA published a common hub for sleep and motor control in the substance nigra, Gad2 neurons are the center of sleep and motor loop control.at present, little is known about the coordination between sleep and motor state. What has been known about sleep is the loss of muscle tension during rapid eye movement (REM) [5].since the neurons involved in motor state and sleep state are extensive and complex, the most effective way to control neural circuits in animals is to share control neurons.however, GABAergic neurons in the substantia nigra reticular region play an important role in motor inhibition [6] and stimulation of multiple arousal neurons [7].therefore, the authors hope to further explore whether GABAergic neurons in this region are involved in brain state transition and coordination.in order to classify the brain and motor states of mice, the authors used home cages to record and monitor the whole life process of mice based on EEG, EMG and video recording.Figure 1: the schematic diagram and data diagram of EEG, EMG and video recording of mice. After detecting the body movement data of mice in the family cage, the body movement can be divided into three categories: movement state (LM), non motion movement state (MV) and non movement state.non motor movement state refers to the action of eating, brushing and combing hair, and posture adjustment, and does not involve the movement of position.but not moving state can be divided into two categories based on EEG and EMG data: quiet wakefulness (QW) and sleep (SL).LM, MV, QW and SL represent the gradual decrease of motor activity, the decrease of muscle wave activity and the increase of δ band of brain wave (Fig. 2).and almost all the transitions between the four states are transitions between two adjacent states, and there are few large state jumps (Fig. 2).Fig. 2 different sleep motor states and transition processes in the home cage experiment of mice. Furthermore, the authors detected the changes of neurons in different states and different state transformation process in the SNR region.through single cell gene expression analysis, it was found that there were two kinds of GABAergic neurons in two separate regions of SNR: PV (parvalbumin) neurons and gad2 (glutamic acid decarboxylase 2) neurons [8].the authors found that the inactivation of gad2 neurons increased the motor state and immobile state, and significantly reduced sleep.however, gad2 photogenetic activation can cause the termination of motor state and the beginning of sleep state. Although PV neurons can also reduce the activity of motor state in mice, it does not affect the sleep state of mice at all.continuous laser activation of gad2 neurons can increase the transition and conversion of lm-mv, mv-qw and qw-sl, and the conversion in the opposite direction is greatly inhibited.in general, the work of Yang Dan's research group revealed that gad2 rather than PV neurons in the reticular area of substantia nigra can promote sleep production, especially the initiation of non REM sleep, and the activation of PV neurons is mainly responsible for the termination of motor state.the whole behavior sequence of lm-mv-qw-sl is promoted by the activation of gad2 neurons. The activation of gad2 neurons will cause the continuous decrease of motor activity and the increase of δ - band of brain waves. Therefore, it is confirmed that gad2 neurons in substantia nigra are the center of sleep and movement control. Campbell, S. 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