Structural Variation within the Amygdala and Ventromedial Prefrontal Cortex Predicts Memory for Impressions in Older Adults

Brittany S Cassidy,Angela H Gutchess

doi:10.3389/fpsyg.2012.00319

Abstract

Research has shown that lesions to regions involved in social and emotional cognition disrupt socioemotional processing and memory. We investigated how structural variation of regions involved in socioemotional memory [ventromedial prefrontal cortex (vmPFC), amygdala], as opposed to a region implicated in explicit memory (hippocampus), affected memory for impressions in young and older adults. Anatomical MRI scans for 15 young and 15 older adults were obtained and reconstructed to gather information about cortical thickness and subcortical volume. Young adults had greater amygdala and hippocampus volumes than old, and thicker left vmPFC than old, although right vmPFC thickness did not differ across the age groups. Participants formed behavior-based impressions and responded to interpersonally meaningful, social but interpersonally irrelevant, or non-social prompts, and completed a memory test. Results showed that greater left amygdala volume predicted enhanced overall memory for impressions in older but not younger adults. Increased right vmPFC thickness in older, but not younger, adults correlated with enhanced memory for impressions formed in the interpersonally meaningful context. Hippocampal volume was not predictive of social memory in young or older adults. These findings demonstrate the importance of structural variation in regions linked to socioemotional processing in the retention of impressions with age, and suggest that the amygdala and vmPFC play integral roles when encoding and retrieving social information.

Highlights

Structural changes to the brain accompany healthy aging (Hedden and Gabrieli, 2004), including cortical thinning, decreased intracranial volume (Salat et al, 2004), and more specific volumetric reductions in subcortical structures (Walhovd et al, 2005)
The current study investigated how structural variation within regions important to socioemotional and explicit memory affects the retrieval of impressions in healthy aging
This study investigated the possibility that older adults’ ability to remember impressions might be associated with structural variation within brain regions previously implicated in socioemotional memory but not a region implicated in explicit memory, whereas young adults’ memory performance might be less affected by structural variability

Summary

Introduction

Structural changes to the brain accompany healthy aging (Hedden and Gabrieli, 2004), including cortical thinning, decreased intracranial volume (Salat et al, 2004), and more specific volumetric reductions in subcortical structures (Walhovd et al, 2005). Aging affects functional engagement of the hippocampus, including working (Mitchell et al, 2000), and episodic (Daselaar et al, 2003) memory processes, recent research suggests the existence of a functional neural mechanism underlying memory for social information, and that involves the recruitment of medial prefrontal cortex in contrast to the hippocampus (Mitchell et al, 2004; Gilron and Gutchess, 2012) Regions within this “social” memory system (e.g., dorsal and ventral medial prefrontal cortex) are recruited when learning and remembering social material, such as autobiographical memories (Gilboa, 2004), self- versus other-related items (Kelley et al, 2002), and impressions (Mitchell et al, 2004; Gilron and Gutchess, 2012). The relative integrity of these regions may be associated with the level of remembered social information in older, but not necessarily younger, adults

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