| Program#/Poster#: |
614.13/WW66 |
| Title: |
Involvement of the lateral amygdala
in early recognition of temporal structure of CS-US association in Pavlovian
fear conditioning. |
| Location: |
Halls B-H |
| Presentation Time: |
Tuesday, Nov 15, 2011, 8:00 AM - 9:00
AM |
| Authors: |
*L. DIAZ-MATAIX1,
R. C. RUIZ-MARTINEZ2, R. SEARS1, J. E. LEDOUX1,3,
V. DOYERE4;
1Ctr. for Neural Sci., New York Univ., NEW YORK, NY; 2Ministry
of Educ. of Brazil, Capes Foundation,, Brasilia-DF, 70359-970, Brazil; 3Emotional
Brain Inst., Nathan S. Kline Inst. for Psychiatric Res., Orangeburg, NY;
4Ctr. de Neurosciences Paris-Sud, CNRS-UMR8195, Univ. Paris-Sud,
Orsay, France |
| Abstract: |
In Pavlovian fear conditioning, a conditioned
stimulus (CS) is paired with an unconditioned stimulus (US). The CS then
comes to elicit conditioned fear responses. The subject not only learns
that the CS predicts the arrival of the US, but also the time when the US
is expected to arrive. In the present experiments, we asked whether the
amygdala, which is crucial for fear conditioning, processes the CS-US interval.
We used a reconsolidation paradigm in rats to test whether a change in the
CS-US interval is detected and triggers the updating of fear memory in the
amygdala. Rats with bilateral cannulae in the lateral amygdala (LA) were
submitted to a strong auditory fear conditioning training paradigm. The
next day, they were presented with a single CS-US trial with the same CS-US
interval or an interval different than during training. Immediately after,
anisomycin (an inhibitor of protein synthesis) or vehicle was infused into
the LA. The next day, freezing to the CS alone was tested. The long-term
memory test indicated that, in this strong training condition, a protein
synthesis dependent reconsolidation was triggered in the amygdala only when
the CS-US interval was different, either earlier or later than during initial
training. No loss of fear memory was observed in the animals for which the
CS-US interval was the same in the test as in training. The same result
was obtained with weak training (2 CS-US training trials). Moreover, rats
exposed to a different CS-US interval during retrieval showed an increase
in the number of Zif-positive cells compared to control animals. Together
these results suggest that a change in the expected time of the US arrival
(US-ETA) triggers an updating of the fear memory in the amygdala through
a reconsolidation process, and rats can learn the time of US arrival in
very few trials. Thus, not only the association between the CS and US is
learned with few pairing during training but also the US-ETA. Moreover,
a change in the expected time of the US arrival triggers plasticity mechanisms
in the lateral amygdala. These results suggest that amygdala is involved
not only in the acquisition and storage of the CS-US association but also
in temporal properties of the association. |
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