LeDoux Lab 2010 SfN Abstracts

Program#/Poster#:	914.21/MMM37
Title:	The involvement of amygdala in the temporal structure
Location:	Halls B-H
Presentation Time:	Wednesday, Nov 17, 2010, 1:00 PM - 2:00 PM
Authors:	*R. C. MARTINEZ1,2,3, L. DIAZ-MATAIX2, S. HOHN4, G. E. SCHAFE5, J. E. LEDOUX2,6, V. DOYÈRE4,2; 1Dept Anat, Univ. Sao Paulo, Sao Paulo, Brazil; 2Ctr. for Neural Science, New York Univ., New York, NY; 3Foundation, Ministry of Educ. of Brazil, Brasilia-DF, Brazil; 4Ctr. de Neurosciences Paris-Sud, CNRS-UMR8195, Univ. Paris-Sud,, Paris, France; 5Dept. of Psychology, Yale University, USA, New Haven, CT; 6The Emotional Brain Inst. and the Nathan S. Kline Inst. for Psychiatric Res., Orangeburg, NY
Abstract:	In recent years, great advances have been made toward describing the neural systems mediating the acquisition of Pavlovian conditioning. In the fear conditioning paradigm, a conditioned stimulus (CS) is paired with an unconditioned stimulus (US), so that the CS comes to elicit conditioned responses. What is learned is not only that the CS predicts the arrival of the US, but also when the US is expected to arrive. In the present experiments, we examined the role of plasticity in the amygdala in learning the CS-US interval. For that, we used immunohistochemistry against Arc protein to test whether a change in the CS-US interval triggers plasticity processes in the amygdala. In a first experiment, we trained rats in an auditory fear conditioned suppression paradigm until they showed the typical temporal pattern of suppression with the maximum response occurring at the expected time of US arrival. Then, the CS-US interval was either shortened (from 30 to 10s) in a single session or not changed. Ninety minutes later, rats were perfused and the brains processed for Arc immunohistochemistry. The results showed a rapid behavioral shift towards the new CS-US duration with faster increase in suppression that peaked at the new expected time of US arrival (10 s) and an increase in the number of Arc-positive cells in the lateral amygdala (LA) compared to animals for which the CS-US interval was not changed. In a second experiment, we asked whether this differential increase in Arc positive cells could be obtained very early in training, with a single learning trial. Rats were submitted to a single session of a strong auditory fear conditioning. The next day, rats were exposed to the same or to a different CS-US interval or not retrieved and perfused 90 min later. An increase in the number of Arc-positive cells in LA was observed in the groups that were retrieved in comparison with the not retrieved group. This increase may suggest that the CS-US interval is learned very early in training. In all, the results from both experiments suggest that a change in the expected time of the US arrival triggers plasticity mechanisms in the lateral amygdala, which may then engage in reconsolidation processes. Thus, the amygdala may be involved not only in the processing of fear memories but also in the recognition of temporal aspects of these memories.
Support:	R37 MH038774 P50 MH058911 R01 MH046516 CNRS-UPS-NYU EmoTime ANR-Memotime