DISSERTATION RESEARCH: A New Model of Fear Conditioning

University Of South Dakota Main Campus, Vermillion SD

Investigators

Abstract

Stressful events in life stimulate powerful emotional responses that help shape future interactions. Often the severity of a stressor depends on an individual's interpretation of the stressor. This sensitivity varies between individuals within a population. Stressful conditions also create learning intensive environments, which are also perceived differently by different individuals. The intersections between stress and learning are of particular importance for adaptation to future circumstances, and the interaction between them and how they vary among individuals is the central focus of this investigation. Recently we have developed a new model of fear conditioning in Rainbow trout, where a neutral sound is paired with a stressful event (losing an aggressive interaction with a larger individual) once a day for several days. After several pairings, test fish associate the neutral sound with getting beaten up, and exhibit a stress response when presented with the neutral sound alone. This stress response includes changes in circulating stress hormones, increased neurotransmitter activity and even suppression of gene activity in regions of the brain associated with learning and memory. This stressful association can be eliminated however, if the test fish learns to escape from the larger fish through a small escape hole, available only during the interactions. These experiments were designed to use this new model to determine if a behavioral conditioned response occurs concurrently with the physiological and neural responses. Variable stress responses within a population are hallmarks of environmental and evolutionary adaptation, and identifying links between divergent stress coping strategies is vital for understanding how stress influences learning. These results will be presented at international conferences encompassing disciplines from fisheries to neuroscience, at which previous presentations have garnered three best talk and poster awards. Additionally, this work has included 5 undergraduate researchers (including 2 women), and has stimulated a cooperative relationship with the United States Fish and Wildlife Service.