Author: Elizabeth Ankudowich

Publisher:

Published: 2018

Total Pages:

ISBN-13:

"Episodic memory encompasses an extraordinary range of diverse cognitive functions that are integral to daily functioning. Healthy aging is associated with declines in episodic memory, which may impair older adults' ability to remember the rich contextual details of previously experienced events. By the age of sixty, older individuals may have a reduced ability to remember spatial or temporal contextual features of past events (e.g., where or when you last took a prescription medication). Previous studies have focused on understanding the anatomical and functional neural correlates of episodic memory decline in young and older adulthood, but how these underlying mechanisms contribute to episodic memory to across the adult lifespan remains to be explored. In this series of studies, we aim to advance our understanding of the differences in episodic memory that develop across the adult lifespan and the neural basis of this age-related decline, as measured by functional magnetic resonance imaging (fMRI). Using a lifespan sample of young, middle-aged, and older adults, we employ a source memory paradigm to assess individuals' memory for the spatial and temporal contextual details of photographs of faces. In addition, we analyze fMRI data collected during both initial encoding and subsequent retrieval of contextual information in order to examine differential effects of age on encoding- and retrieval-specific processes. In Study 1, we demonstrate that declines in source memory may be discernible by midlife, extend into older adulthood, and are associated with reduced modulation of phase-specific activity in anterior prefrontal (PFC) and posterior ventral visual areas. We also show that older adulthood may be associated with increased phase-specific modulation, particularly in areas of lateral PFC and medial temporal lobes (MTL) at retrieval. In Study 2, we extend these findings to show how lifespan differences in phase-specific activity directly contribute to source memory performance. In particular, we find that older individuals engage dorsolateral PFC (DLPFC) to a greater extent at encoding and hippocampus (HC) to a greater extent at retrieval, during the phase when it does not seem to help performance across individuals. In Study 3, we address whether these age-related increases in encoding- or retrieval-specific activation might be related to differences in whole-brain connectivity. We examine whether age-related increases in DLPFC (Study 2 encoding) and posterior HC (Study 2 retrieval) differentially correlate with activity across the rest of the brain and with performance. In young adults, we demonstrate that connectivity between lateral PFC, parietal, and ventral visual cortical regions and our DLPFC seed relates to better performance. In older adults, these same regions show greater connectivity with posterior HC and relate to worse performance. Converging findings across studies suggests that activity and connectivity among fronto-parietal regions support the recollection of visual information and source memory performance in young adults, whereas aging may be associated with altered modulation of fronto-parietal activity and connectivity with posterior HC, which does not support source memory performance." --