Understanding the effects of experimental brain injury to extinction of active avoidance

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Project Summary (from parent grant R21 NS119991) Our goal is to address an emerging challenge that we face with the effects of brain injury to neurological function and mental health. A broad class of brain damage is diffuse injury (e.g. concussion) produced experimentally using a closed head injury by weight drop onto the head. Concussion occurs with an impact to the head plus angular acceleration which may result in axonal damage that disrupts communication and activity between brain regions, likely affecting mental health by impairing emotional regulation. Two important forms of emotional regulation are extinction and avoidance of rewarding stimuli. Extinction is the basis of exposure treatment for fear and anxiety disorders. Avoidance of situations that trigger fear memories is a hallmark of many mental health disorders. Patients with brain injury display excess avoidance, thus reducing the attainment of rewards, which is detrimental to recovery. To evaluate the potential relationship between brain injury and avoidance, a biological link must be examined using reliable injury models and behavioral tests. There are homologous brain regions in rodents and humans for avoidance. Avoidance requires interactions between the amygdala, medial prefrontal cortex, and ventral striatum. Overall, this work will answer a series of key questions about the impact of brain injury to extinction and avoidance. Moreover, this work will increase the base of scientific and public health evidence on this important subject.