Amygdala Underlies the Environment Dependency of Defense Responses Induced via Superior Colliculus.

Kaoru Isa,Kota Tokuoka,Tadashi Isa,Sakura Ikeda,Sara Karimi,Thongchai Sooksawate,Kenta Kobayashi

doi:10.3389/fncir.2021.768647

Abstract

In our previous study, we showed that the defense responses induced by the selective optogenetic activation of the uncrossed output pathway from the deeper layer of the superior colliculus were environment dependent in the mouse. In a small closed box, the stimulus frequently induced flight (fast forward run away) responses, while in a large open field, the stimulus tended to induce backward retreat responses. We tested a hypothesis that the amygdala is involved in such environment dependency of the innate defense responses. For this purpose, we made a bilateral lesion of the amygdala induced by the ibotenic acid injections in male mice. As a result, in the mice with lesions of substantial portions of the basolateral and basomedial complex, the flight responses in the closed box disappeared and retreat responses were mainly induced. The retreat responses on the open platform were unchanged. Classically, the amygdala has been considered to be involved in the memory-dependent contextual modulation of the fear responses. In contrast, the present results suggest a novel view on the role of the amygdala in which the amygdala plays a key role in sensing the current environmental setting for making a quick decision of action upon emergency, which is critical for survival in the natural environment.

Highlights

In case you are attacked by a predator coming from above, what would you do? According to the predatory imminence theory, if the animal senses the approach of a predator, it may exhibit speciesspecific defense reactions such as freezing to avoid being detected by the predator (Bolles, 1970)
Among the 57 mice, including 36 sham-lesioned mice and 21 mice with amygdala lesion induced by the ibotenic acid injection, 11 sham-lesioned mice and 10 mice with bilateral amygdala lesion exhibited successful expression of ChR2 throughout the superior colliculus (SC) defense pathway with vigorous motor responses to the optogenetic stimulation, and successful accomplishment of all the experimental procedures were initially selected for further analysis
The pseudoquantitative rankings of lesion extent in and around the amygdala, including the caudate/putamen (CPu), piriform cortex (Pir), endopiriform claustrum (En), and hippocampus (Hip), are indicated in Table 2, which will be argued about the behavioral effect

Summary

Introduction

In case you are attacked by a predator coming from above, what would you do? According to the predatory imminence theory, if the animal senses the approach of a predator, it may exhibit speciesspecific defense reactions such as freezing to avoid being detected by the predator (Bolles, 1970). Once the animal is detected by its predator and a threat is imminent, freezing may not be the optimal behavior for survival. The strategy for you to defend yourself from the predator may depend on the environment in which you are placed. Such behavioral responses should be innately imprinted in your nervous system. Which neural system in the brain works for you to integrate the knowledge of your current environmental settings and how your enemy is approaching, for you to make a quick decision for the best strategy to defend yourself? What is the neural basis of an innate environment-dependent decision of defense strategy? Which neural system in the brain works for you to integrate the knowledge of your current environmental settings and how your enemy is approaching, for you to make a quick decision for the best strategy to defend yourself? In other words, what is the neural basis of an innate environment-dependent decision of defense strategy?

Methods

Results

Conclusion