*D. E. BUSH, F. SOTRES-BAYON, J. E. LEDOUX;
Ctr. Neural Sci., New York Univ., New York, NY

Individual differences in emotional learning may contribute to anxiety disorder susceptibility. This has motivated a growing interest in biological factors that promote resilience in the face of adversity. Animal research on the neural basis of fear conditioning and extinction has identified the amygdala as crucial for both of these aspects of emotional learning. This work has typically focused on average levels of behavioral responding, despite the existence of considerable differences among individuals exposed to identical training and extinction procedures. However, understanding the mechanisms underlying individual differences in fear reactivity and fear recovery will be crucial for advancing understanding of anxiety disorders in humans. To begin investigating the nature and causes of fear variability and resilience, we separated samples of outbred Sprague-Dawley rats into phenotypic groups characterized by high/low fear reactivity, or fast/slow fear recovery. Fear reactivity phenotypes were established based on freezing responses during fear conditioning, and then tested for reactivity on subsequent days. Fear recovery phenotypes were established based on freezing reduction observed during an early phase of extinction learning, and then tested for extinction retrieval on the following day. Individual differences in fear reactivity emerged during conditioning, remained stable over subsequent tests, and were context-independent. Individual differences in fear recovery emerged during early extinction training, and remained for the extinction retrieval test, even though the fast/slow recovery phenotypes showed similar fear levels at the beginning and ending of fear extinction training. These observations suggest that the two aspects of resilience proposed by Yehuda et al. (2006)--high resistance and fast recovery--are modeled here in rats with low fear reactivity and fast recovery, respectively. Since clinical disorders may reflect extreme phenotypes, identification of the biological basis for these differences could provide insights into human individual differences in fear and resilience.

Support Contributed By: NIH Grants R01 MH46516, R37 MH38774, K05 MH067048, P50 MH58911, R21 MH072279

Program No. 307.3/BBB16
Poster presentation:Sunday, Nov 04, 2007, 3:00 PM - 4:00 PM
Location: San Diego Convention Center: Halls B-H