LeDoux Lab 2010 SfN Abstracts

Program#/Poster#:	914.16/MMM32
Title:	Acquisition of sidman active avoidance in rats depends on the lateral and basal, but not central, nuclei of the amygdala
Location:	Halls B-H
Presentation Time:	Wednesday, Nov 17, 2010, 4:00 PM - 5:00 PM
Authors:	*G. LAZARO-MUNOZ1, J. E. LEDOUX1,2, C. K. CAIN1,2; 1Ctr. Neural Sci., New York Univ., NEW YORK, NY; 2The Emotional Brain Inst. and The Nathan Kline Inst., Orangeburg, NY
Abstract:	The amygdala is critical for conditioned defensive behaviors. The lateral (LA) and central (CE) amygdala nuclei are critical for the acquisition and expression of simple Pavlovian fear conditioning. Unlike LA and CE, the basal (B) amygdala is not necessary for fear conditioning; pre-training lesions of this nucleus do not impair fear acquisition or expression. In contrast, acquisition and performance of instrumental active avoidance (AA) are severely impaired by lesions of LA or B, but not of CE (Choi et al, 2010; Lázaro-Muñoz et al, 2010). These findings support a model of amygdala function in aversive learning (Amorapanth et al, 2000) where LA acquires and stores Pavlovian associations between conditional stimuli (CSs) and aversive unconditional stimuli (USs), CE mainly receives this information and orchestrates Pavlovian fear reactions, and B uses the aversive CS to reinforce and motivate instrumental action. In AA, rats can terminate threatening CSs and prevent delivery of painful USs by performing an instrumental response. However, early in training rats fail to respond, leading to Pavlovian conditioning where environmental cues are paired with the US. In a typical AA protocol, rats can also escape the US, usually by performing the same response that is required for avoidance. Thus, behavior during AA training typically progresses from Pavlovian freezing, to improved escaping of the US and finally to active avoidance of the US. Interestingly, AA tends to be acquired more readily when escape and avoidance responses match, suggesting that escape behavior acts as an important bridge between Pavlovian reactions and instrumental actions. However, the contributions of LA, B and CE to escape behavior during AA training have never been examined. We evaluated escape behavior in rats receiving electrolytic lesions of LA, B or CE before Sidman AA training. 2-way shuttling was the AA response, brief footshocks (1 mA x 0.5s) were the USs and contextual cues were the CSs. Lesions had no effect on the total escapes, however, LA lesions severely prolonged escape latency. CE lesions reduced escape latency although this effect was not significant. Rats with pre-training B lesions were indistinguishable from controls. Thus, like Pavlovian reactions and instrumental actions, LA contributes to escape behavior during AA training. However, unlike these behaviors, escape does not depend on B or CE. This suggests that another LA output may modulate escape during AA and affect the transition from Pavlovian freezing to active avoidance. One possibility is the medial nucleus, which receives LA afferents and projects to the dPAG, a region known to be involved in escape behavior.
Support:	MH38774
	MH086294
	MH077458