Decision Mechanism Study Of Defensive Behavior Induced By Innate Fear

The ability of animals to respond to different life-threatening stimuli and take the most adaptive defensive behavior is essential for survival and breeding.Existing studies have found that the superior colliculus(SC)is the core brain area of the subcortical neural circuit that mediates the defensive behavior of instinct.Activation of neurons in the superior colliculus can induce freezing or flight occur,but it is unclear how SC induced these two behaviors.In this paper,through the functional analysis of the neurons within the superior colliculus,we have a better understanding of the brain area and the defense response decision mechanism under instinct fear.Firstly,we selected three types of neurons in SC,ETV1~+neurons,Ntsr1~+neurons and Tac1~+neurons,of which Ntsr1~+neurons and Tac1~+neurons belong to the Wild Field neuron category.Then,we used optogenetic technology to activate these three neurons separately,using a random stimulation system to stimulate the mice and conduct behavior analysis and statistics.After the experiment,we verified the virus injection and expression.Finally,we found that the three neurons have different functions in the defense response.Activate ETV1~+neurons,mice may freeze or escape,and then find that different light stimulation frequencies can induce different defense behaviors in mice.Low frequency light activates the neurons,and mice tend to freeze.At high frequencies,mice have a high probability to flight.Both activated Ntsr1~+and Tac1~+neurons showed freezing behavior,but they were different.Activated Ntsr1~+mice showed only short-term freezing behavior,while activated Tac1~+neurons showed only long-term freezing behavior.This subject has a further understanding of the function of the subclass neurons of the superior colliculus and the decision-making mechanism of the defense response.