The cingulate cortex of older adults with excellent memory capacity

Abstract

Memory deterioration is the earliest and most devastating cognitive deficit in normal aging and Alzheimer’s disease. Some older adults, known as “Supernormals”, maintain excellent memory. This study examined relationships between cerebral amyloid deposition and functional connectivity (FC) within the cingulate cortex (CC) and between CC and other regions involved in memory maintenance between Supernormals, healthy controls, and those at risk for Alzheimer’s disease (amnestic mild cognitive impairment). Supernormals had significantly stronger FC between anterior CC and R-hippocampus, middle CC (MCC) and L-superior temporal gyrus, and posterior CC and R-precuneus, while weaker FC between MCC and R-middle frontal gyrus and MCC and R-thalamus than other groups. All of these FC were significantly related to memory and global cognition in all participants. Supernormals had less amyloid deposition than other groups. Relationships between global cognition and FC were stronger among amyloid positive participants. Relationships between memory and FC remained regardless of amyloid level. This revealed how CC-related neural function participates in cognitive maintenance in the presence of amyloid deposition, potentially explaining excellent cognitive function among Supernormals.

Identification of Successful Cognitive Aging in the Alzheimer’s Disease Neuroimaging Initiative Study

“…We incorporated a broad assessment of EF (visuospatial, attention, working memory, and verbal fluency) into the measures of cognitive functioning in the present study. EM has been the most frequently used determiner of successful cognitive aging in the literature [6, 7]. However, individuals with excellent EM do not necessarily have equivalent EF [7].…”

“…Recent literature, however, suggests that there is inter-individual variability in the maintenance of cognitive capacities in old age [3-5]. Some older adults have superior cognitive capacities compared to age- and education-matched cognitively normal older adults [6, 7] or even when compared to cognitively normal younger or middle-age individuals [8-11]. Some retain excellent cognitive capacities over decades [12-14].…”

“…Some retain excellent cognitive capacities over decades [12-14]. These emerging studies encourage more research to better understand the nature of “successful cognitive aging” or even so-called “Supernormals” [6, 7] or “Superagers” [9]. …”

“…More recent cross-sectional case-control studies have started identifying neurobiological mechanisms related to successful cognitive aging. These studies suggest that differences in brain structure and function, especially in the cingulate cortex, prefrontal cortex, and medial temporal lobe, may be related to differences in cognitive abilities ranging from above average to deficient [6, 8, 11]. However, it is unclear if these neurobiological differences are due to aging-associated neurodegeneration or to AD-specific pathology.…”

“…However, it is unclear if these neurobiological differences are due to aging-associated neurodegeneration or to AD-specific pathology. In our recent work, we found that older adults with excellent EM had less AD pathology, indexed by whole-brain cerebral amyloid deposition [6]. These aging adults also were less affected by aging-associated neurodegeneration indexed by a network promoting increased nitric oxide bioavailability [7].…”