*M. R. DELGADO1, R. L. JOU2, J. LEDOUX3, E. A. PHELPS2; 1Dept Psychol, Rutgers Univ., Newark, NJ; 2Psychology, 3Ctr. for Neural Sci., New York Univ., New York, NY

Physiological expressions of fear are quickly exhibited when a threat is imminent (e.g., a dog’s angry bark). Learning how to avoid a negative outcome is an adaptive mechanism that, in the face of such threats, promotes the integration of action (e.g., run) and motivation (e.g, terminate or reduce fears) responses. Previous research across species has shown that the amygdala is critical for learning about fears. However, less is known about the role of the human amygdala and other regions in learning how to avoid negative outcomes. One potential mechanism for active avoidance of stressful situations is postulated to involve amygdala-striatal interactions. The goal of this study was to investigate the physiological and neural correlates underlying avoidance learning in humans. Specifically, we used a classical conditioning paradigm where three different conditioned stimuli (CS) were presented. One stimulus (e.g., a blue square) predicted the delivery of a shock (CS+) upon stimulus offset, while another (e.g., a yellow square) predicted no negative consequences (CS-). A third conditioned cue (e.g., a purple square) also predicted delivery of a shock, but participants were instructed that upon seeing this stimulus, they could avoid the shock if they entered the correct sequence of numbers from a keypad (AV_CS+). After successful learning of the sequence, participants could then easily terminate the shock during subsequent stimulus presentations (AV_CS-). A conditioned response, measured by increases in skin conductance responses, was observed when comparing CS+ and CS- trials, but also when comparing AV_CS+ and CS- trials. Further, such responses were diminished after avoidance learning (AV_CS-). As expected, based on previous fear conditioning studies, increases in blood oxygenation level dependent (BOLD) responses in the amygdala were observed during a contrast between all shock trials versus CS-. Interestingly, BOLD responses in both dorsal and ventral striatum were also observed, with increased responses when the motivation to avoid a potential shock was high (AV_CS+); that is, when participants had an opportunity to influence the outcome of the trial. Such signals were not observed for the same stimulus after successful avoidance learning (AV_CS-). The data is consistent with animal models and further suggests that interactions between the amygdala and the striatum may mediate the avoidance of conditioned fear in humans.

Support Contributed By: James S McDonnell Foundation


Program No. 97.1/WW1
Poster presentation:Saturday, Nov 3 2007 1:00 PM - 2:00 PM
Location: San Diego Convention Center: Halls B-H