The Neural Circuits And Formation Of Visual Innate Fear Defensive Responses In Mice

Fear emotion to imminent threatening environmental stimuli is essential for the survival of animals.Defense response which evoke by fear emotion is initial for the approaching danger.Visual information was of fundamental importance for many animal species due to evolution,which could evoke innate defense response to avoid predator.When received the information from eyes,the brain could recognize the danger signal and make the defensive decision.How does visual system quickly detect dangerous information from environment? Whether a specific cell types in the visual system for innate defensive response? When the formation of this visually-evoked defensive response first occurs at the early postnatal stage? What is mechanism of visually-evoked defensive response?Here,by using the optogenetics,patch clamp and two-photon excitation microscopy and calcium image and other techniques,combined with looming stimulus behavioral paradigms,we found that 1)Looming stimulation in mice evoked flight behavior had fully developed by P20-24.2)Visual-evoked innate defensive response was not significantly altered by sensory deprivation at an early postnatal stage.3)More SC neurons in prepubescent mice respond to looming stimuli than in pups.4)The percentage of wide-field and horizontal cells of all recorded cells in the superior colliculus were notably elevated at P20–24,it is likely that they contribute to the function underlying innate defensive responses.Therefore,we indicate that that looming stimulation in mice evoked flight behavior commencing at P14–16 and had fully developed by P20–24.Furthermore,the percentages of wide-field and horizontal cells in the superior colliculus were notably elevated at P20–24,which are likely to make contribution fot the innate defensive responses.Then,we focus our work on the neural mechanism of innate defensive behavior: 1)Circuitry architecture whereby calretinin（CR）positive retinal projections to the SC initiate a process for fear-related sensorimotor transformation in mice.2)The neural circuit from CR⁺ RGCs → 5HT2c⁺ neurons in the medial lower SC made the main contributor to trigger flight escape action.3)The mechanism of SC→VTA^GABA+→Ce A pathway in adult mice,which mediated visual innate defensive behaviors.4)The m STN→LGP circuit regulated priority decision between sleep and innate defense response.Our finding reveals the neural mechanism of visually-evoked innate defensive behavior,which could increase the understanding of the innate defensive responses.Dysfunction on neural circuits of innate fear defensive response could induce the autism or phobia disorder.Therefore,the mechanism of neural circuits on visual innate defensive response might be increasing understanding of interaction between visual information and fear emotion.If we could figure out the character of visual pathway or specific cell type in the brain,which might provide an evidence base for clinical research of mental disorder in future.