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The role of cholinergic input from the medial septum in cued and contextual fear extinction memory.

Staib JM, Knox D (2016) The role of cholinergic input from the medial septum in cued and contextual fear extinction memory. Neuroscience 2016 Abstracts 262.11 / III7. Society for Neuroscience, San Diego, CA.

Summary: In classical fear conditioning, a neutral stimulus (CS) is paired with an aversive stimulus (US), causing the animal to associate the US with CS, and display a fear response to the CS. Fear extinction occurs when the CS is presented without the US and the animals learn that the CS no longer predicts the US, thus learning to no longer show fear with CS presentation. Ventral medial prefrontal cortex inhibition of neural activity in basolateral and central amygdala nuclei is critical for extinction memory formation. Recently, we observed that cholinergic lesions in the Medial Septum and Diagonal Bands of Broca (MS/DBB), induced with 192-IgG saporin results in fear extinction memory deficits and contextual fear memory generalization between the conditioning and extinction contexts. While this suggests that MS/DBB cholinergic neurons may be a component of the fear extinction circuit, these neurons project to many brain regions. As a result, the MS/DBB cholinergic efferents that are critical for mediating extinction memory and contextual fear memory discrimination are unknown. The goal of the present study is to isolate the exact MS/DBB efferents that mediate extinction memory and contextual fear memory discrimination. While the study is in progress, some results have been collected. Cholinergic lesions in the dorsal hippocampus, ventral hippocampus, and medial prefrontal cortex have no effects on fear extinction memory or contextual fear memory discrimination. This is surprising because all of these regions are components of the fear extinction circuit and the dorsal hippocampus is critical for contextual learning during acquisition of fear and extinction memory. The MS/DBB also projects to habenula nuclei, and there are cholinergic interneurons in the MS/DBB as well. For the remainder of the study, we explore the potential role of MS/DBB cholinergic input to the habenula and MS/DBB cholinergic interneurons in mediating extinction memory and contextual fear memory discrimination. Isolating a region that has a direct role in mediating extinction memory could help focus future research in fear memory disorders like post traumatic stress disorder.

Related Products: 192-IgG-SAP (Cat. #IT-01)