Youthful Brains in Older Adults: Preserved Neuroanatomy in the Default Mode and Salience Networks Contributes to Youthful Memory in Superaging

Abstract

Decline in cognitive skills, especially in memory, is often viewed as part of "normal" aging. Yet some individuals "age better" than others. Building on prior research showing that cortical thickness in one brain region, the anterior midcingulate cortex, is preserved in older adults with memory performance abilities equal to or better than those of people 20 -30 years younger (i.e., "superagers"), we examined the structural integrity of two large-scale intrinsic brain networks in superaging: the default mode network, typically engaged during memory encoding and retrieval tasks, and the salience network, typically engaged during attention, motivation, and executive function tasks. We predicted that superagers would have preserved cortical thickness in critical nodes in these networks. We defined superagers (60 -80 years old) based on their performance compared to young adults (18 -32 years old) on the California Verbal Learning Test Long Delay Free Recall test. We found regions within the networks of interest where the cerebral cortex of superagers was thicker than that of typical older adults, and where superagers were anatomically indistinguishable from young adults; hippocampal volume was also preserved in superagers. Within the full group of older adults, thickness of a number of regions, including the anterior temporal cortex, rostral medial prefrontal cortex, and anterior midcingulate cortex, correlated with memory performance, as did the volume of the hippocampus. These results indicate older adults with youthful memory abilities have youthful brain regions in key paralimbic and limbic nodes of the default mode and salience networks that support attentional, executive, and mnemonic processes subserving memory function.

Neuroimaging markers associated with maintenance of optimal memory performance in late-life

“…Our finding that Optimal Memory Performers had larger hippocampal volumes compared with their Typically-performing peers is consistent with recent work showing that SuperAgers exhibit more “youthful” paralimbic and limbic structures (Sun et al, 2016) and less age-related cortical atrophy (Harrison et al, 2012). While there was no association between Optimal vs.…”

The cingulate cortex of older adults with excellent memory capacity

“…Two of the regions showing stronger connectivity to CC in Supernormals (R-hippocampus and R-precuneus) are involved in episodic memory and the default mode network (DMN). As a number of studies have examined the relationship between aging and episodic memory (Tromp, et al, 2015), aging and DMN acitivity (Greicius, Srivastava, Reiss, & Menon, 2004), or brain volume within DMN among Supernormals (Sun et al, 2016), our results further validate the brain function and episodic memory in the Supernormals. For example, decreased FC between PCC and precuneus occurs in the early stages of AD (Binnewijzend et al, 2012; Zhang et al, 2009), and positive relationships between memory performance and FC in ACC and hippocampus were found in cognitively normal older adults (Arenaza-Urquijo et al, 2013; Li et al, 2014).…”

“…Furthermore, compared to other brain regions, including medial temporal/hippocampal and prefrontal lobes, CC is affected by amyloid deposition early in both aging and AD (Camus et al, 2012; Chang et al, 2015; La Joie et al, 2012). Notably, in an emerging structural imaging study examining the default neural networks, cortical thickness was preserved in multiple cingulate, hippocampal, and frontal regions among Supernormals when compared to their younger counterparts (Sun et al, 2016). In resting-state functional MRI (rs-fMRI) studies of cognitively normal (but not necessarily cognitively excellent) older adults, greater FC between anterior (ACC) and posterior CC (PCC), between ACC and prefrontal cortex, or between PCC and hippocampus have been correlated to higher education, often used as a surrogate for intelligence, and overall better cognitive function (Arenaza-Urquijo et al, 2013; Shu et al, 2016; Wang et al, 2010).…”

Perceptual and memory inhibition deficits in clinically healthy older adults are associated with region-specific, doubly dissociable patterns of cortical thinning.

“…The “Brain Maintenance” theory posits that ‘individual differences in the manifestation of age-related brain changes and pathology allow some people to show little or no age-related cognitive decline’ (Nyberg et al, 2012, p. 295). Sun and colleagues (2016) recently reported that ‘superagers’ –those older adults “with memory performance abilities equal to or better than those of people 20–30 years younger” (p. 9659) had reduced cortical thinning relative to age-matched “normal” older adults in several key large-scale intrinsic brain networks that support memory processes, which correlated with memory performance. In the current data, the finding of a double dissociation between different measures of cortical thickness and types of inhibition, which were not significantly associated with each other, suggests that there may be distinct trajectories of cortical thinning that predict individual differences in cognitive morbidity across subtly-different cognitive tasks, even in clinically healthy older adults.…”