Motor behavior is the only way for humans and animals to interact with the outside world and essential for life. In a competing environment, animals often execute a series of motor behaviors to complete the motor tasks, such as defensive escape sequence. Facing with danger, animals implement the escape behavior to alter movement direction avoiding the danger and transit subsequently to fast forward locomotor movement fleeing away from danger. It is instinctive for organism to coordinate the motor behaviors of "escape" and "swim" and execute them in a temporal and smooth manner to avoid predation or dangers. We discovered a class of spinal excitatory interneuron subtypes (esV2a) determining the directionality of the. We reconstructed the neuronal circuits controlling escape by serial block-face electron microscopy and multiple whole-cell patch-clamp recording. Therefore, the mechanism underlying action selection is not only determined by the brain, but also by the "brain-spinal cord". Furthermore, we revealed a neural mechanism the defensive motor sequence in zebrafish. By combining two-photon calcium imaging and whole-cell patch-clamp recording, we demonstrated Mauthner cell (M-cell), cranial relay neuron (CRN) and nucleus of the medial longitudinal fascicle (nMLF) are successively wired via excitatory synapses, which form a neuronal circuit chain allowing neural signals to transmit unidirectionally. The construction of the neural circuit chain endows animals to perform defensive escape sequence to rapidly change the movement direction by escape and flee away from the danger. 

Sleep and wake is important and highly conserved behaviors across species. Normal sleep maintains body function and mental health for human. Studies of brain circuitry controlling sleep-wake cycle focused on fast neurotransmitters, such as glutamate and GABA, while the monoaminergic systems also play essential roles in sleep-wake control by producing widespread effects to induce global changes in brain state. Arousal is the physiological and psychological state of staying awoken or of sensory stimulation to the perception. Arousal is important in regulating consciousness, attention, alertness, and information processing. It involves activation of the ascending reticular activating system (ARAS) in the brain, which regulates wakefulness, the autonomic nervous system, and the endocrine system, leading to the increased heart rate and sensory alertness desire and readiness to respond. Early studies suggested an essential and complicated role of 5-HT system in sleep-wake regulation as well as arousal, the mechanism of which remains elusive. In the lab, we focus on how 5-HT neurons in the dorsal raphe nucleus (DR) regulate the above behavior states.

Extensive spontaneous locomotor recovery after spinal cord injury (SCI) has been observed in the hemisection SCI models of adult mice, adult rats and adult monkeys as well as in the transection SCI model of adult zebrafish. These data suggest that the spontaneous locomotor recovery is primarily attributed to the newly establishment of spinal local circuits mainly formed by spinal CPG interneurons displaying remarkable axon regrowth. We found that after adult zebrafish complete SCI over 80% of the axon-regrown spinal interneurons are glutamatergic, while glycinergic interneurons comprise less than 10% of the whole population. The ratio of long projecting glutamatergic interneurons to glycinergic interneurons greatly increased after SCI indicating that the reestablishment of spinal CPG neural circuits in SCI zebrafish mainly depends upon restoration of excitation mediated by axon regrowth of excitatory glutamatergic interneurons. This suggests a potential target for gene and cell therapy of spinal cord injury.