Gamma oscillations in basolateral amygdala during escape behaviors: Observations in a group

Abstract

The basolateral nucleus of the amygdala (BLA) is thought to be essential for rapid escape. These are often thought to be comprised of feedforward action of BLA on the central amygdala. Neither well-understood nor often considered are BLA dynamics during escape behavior, which likely cause neural oscillations particularly in gamma band oscillation (GBO, 30 - 80 Hz). Indeed, GBOs are known to occur in BLA and their occurrence is associated with regulation of emotion, and yet their association with escape behavior remains unknown. To address this, we used a novel technique, cBRAIN (collective brain research aided by instant neurodisplay) to monitor GBO of BLA in a group-housed mice during escape behavior. The headstage of cBRAIN features in (i) wireless recording and transmission of raw data, (ii) blue LED light for tracking the position of the animal, and (iii) red LED light for signaling certain brain activity. We set the threshold for red LED so that it turns on when GBO power exceeds the confidence level of baseline GBO power. In an arena (60 cm x 60 cm), we divided the zone into safe and threat zones with a diagonally cross-sectioning wall. We tested the individual behavior first by applying cBRAIN in one mouse. We observed GBO occurred more frequently when a threat (spider robot) was introduced to the animal. GBO occurred more or less transiently rather than in an ongoing way and the occurrence of GBO was noticeable when the threat was firstly introduced or attack the animal. On the other hand, GBO occurrence was reduced after the animal successfully escaped from the threat zone to the safe zone. Next, we applied cBRAIN in a group of 8 mice. All 8 mice were placed in the threat zone at the beginning. Likewise, GBO occurred more frequently as the robot was introduced and diminished as the most of the group escaped to the safe zone. But interestingly, the GBO occurrence was significantly less frequent in a group compared to the individual test. Moreover, in many cases, the most dominant mice did not present the GBO when the robot introduced to the threat zone, which was different from its individual test. To sum up, GBO in BLA is associated with escape behavior and the occurrence rate is altered with a company as per its social ranks.