Dr. Travis Todd, a Postdoctoral Fellow in Professor David Bucci’s laboratory, has received a National Research Service Award from the National Institute of Mental Health. Dr. Todd’s grant, entitled “Cortico-hippocampal Contributions to Context and Extinction Learning,” will focus on how a part of the brain known as the retrosplenial cortex (RSC) is involved in forming memories about fear-provoking stimuli. Importantly, this work will also emphasize the neural substrates of fear extinction, an animal model of cue-exposure therapy in humans. This research will provide a deeper understanding of cue-exposure therapy, a commonly employed therapy used to treat a variety of human disorders (e.g., post-traumatic stress disorder: PTSD, anxiety related disorders, phobias). Further, by investigating a brain region (the retrosplenial cortex) that is known to be compromised in human disorders such as schizophrenia and Alzheimer’s disease, the proposed experiments may inform clinical practice and treatments for these disorders.
Learning processes allow organisms (including humans) to adapt their behavior to changes in the environment, and are thus crucial for survival. However, learning does not take place in a vacuum. Indeed, most learning experiences occur within complex environments composed of visual, auditory, olfactory, and tactile stimuli. To successfully learn about biologically significant events (e.g., the presence of food or prey) that occur within particular environments, animals must first combine individual features of the environment into an integrated memory, or “context” representation. Contemporary research suggests that this type of learning occurs within cortico-hippocampal networks in the brain. However, the exact pathways and individual functions of particular regions essential for learning about contexts have not been fully resolved. The experiments that will be conducted by Dr. Todd will test the overarching hypothesis that the restrosplenial cortex (RSC) is essential for forming integrated context representations, and that the postrhinal cortex (POR) is essential for updating these memories. This research addresses unanswered questions about the neural substrates of contextual fear learning and also addresses the functional role of RSP and POR in the recovery of fear to a previously extinguished fear cue. Fear extinction is context specific, and recovery can result either from re-experiencing the aversive event (i.e., reinstatement) or when a significant amount of time has passed since fear extinction occurred (i.e., spontaneous recovery). To carry out these experiments, Dr. Todd will use a new and innovative technique: Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to temporally inactivate the RSC and/or POR. This temporary inactivation will allow for isolation of the role of these regions during encoding and/or retrieval processes.