Delineating neural substrates of learning and memory impairments in older adults with depressive symptoms

Abstract

Depression occurring in older people is often associated with cognitive impairment, underlying brain changes, treatment resistance and disability. Impairments in the domain of learning and memory are particularly problematic as these tend persist despite depression symptom resolution. Furthermore, learning and memory impairments have been directly linked to hippocampal atrophy, which in turn has been associated with ongoing cognitive decline and dementia, longitudinally. However, the relationship between depression in older age, and learning/memory impairments, as well as underlying processes contributing to these deficits remains unclear. Contained within this thesis are a series of three published studies. Each examines learning and memory impairments in a clinical sample aged over 50 years whom have a lifetime diagnosis of major depression. The studies examine learning and memory performance with respect to hippocampal size, and its role in Mild Cognitive Impairment, in-vivo neurochemical markers of hippocampal neuronal integrity, and the anterior caudate nucleus, a subcortical structure that has been previously identified as being linked to clinical outcomes, and pathophysiology. The findings of these empirical studies thesis demonstrates the critical link between both hippocampal and caudate nucleus integrity and their role in specifically mediating memory performance, and have important implications for pathophysiology and early intervention models.