Longitudinal brain structure and cognitive changes over 8 years in an East Asian cohort.

Although East Asia harbors the largest number of aging adults in the world, there is currently little data clarifying the longitudinal brain-cognition relationships in this group. Here, we report structural MRI and neuropsychological findings from relatively healthy Chinese older adults of the Singapore-Longitudinal Aging Brain Study cohort over 8 years of follow up (n=111, mean age=67.1 years, range=56.1-83.1 years at baseline). Aging-related change in structural volume was observed, with total cerebral atrophy at -0.56%/year, hippocampal atrophy at -0.94%/year and ventricular expansion at 3.56%/year. Only speed of processing showed an aging-related decline, while other cognitive domains were relatively maintained. Faster decline in global cognition was associated with total cerebral, hippocampal and gray matter volume losses over time. Faster total cerebral atrophy and white matter atrophy (frontal and parietal regions) was associated with faster decline in verbal memory. Hippocampal atrophy and ventricular expansion were both associated with greater decline in verbal memory and executive function. Our findings provide a benchmark for research on brain structural and cognitive changes with aging in East Asians.

Differential age-dependent associations of gray matter volume and white matter integrity with processing speed in healthy older adults.

Slower processing speed (PS), a highly robust feature of cognitive aging, is associated with white matter (WM) deterioration and gray matter volume (GMV) loss. Traditional linear regression models assume a constant relationship between brain structure and cognition over time. To probe for variation in the association between WM and GMV and PS over time, we used a novel sparse varying coefficient model on data collected from 126 relatively healthy older adults (67 females, aged 58-85years) evaluated with MRI and a standardized neuropsychological test-battery. We found that WM microstructural differences indexed by fractional anisotropy values in the fronto-striatal tracts (internal and external capsule) showed a stronger association with PS before the age of 70years. Contrastingly, GMV values of the left putamen and middle occipital gyrus were more strongly correlated with PS after 70years. Additionally, within GM and WM compartments, there was heterogeneity in the temporal sequence in which different cortical and subcortical elements were most strongly associated with PS. Together, these observations provide a more nuanced account of the relationships between different structural components of the aging brain and processing speed, a key cognitive domain affected in relatively healthy older adults.

Hippocampal region-specific contributions to memory performance in normal elderly.

To investigate the relationship between regional hippocampal volume and memory in healthy elderly, 147 community-based volunteers, aged 55-83years, were evaluated using magnetic resonance imaging, the Groton Maze Learning Test, Visual Reproduction and the Rey Auditory Verbal Learning Test. Hippocampal volumes were determined by interactive volumetry. We found greater age-related reduction in the volume of the hippocampal head relative to the tail. Right hippocampal tail volume correlated with spatial memory on the Groton Maze Learning Test while left hippocampal body volume was associated with delayed verbal memory. These associations were independent of age, sex, education and speed of processing and support the notion of functional differentiation along the long axis of the hippocampus.

Cognitive function and brain structure correlations in healthy elderly East Asians.

We investigated the effect of age and health variables known to modulate cognitive aging on several measures of cognitive performance and brain volume in a cohort of healthy, non-demented persons of Chinese descent aged between 55 and 86 years. 248 subjects contributed combined neuropsychological, MR imaging, health and socio-demographic information. Speed of processing showed the largest age-related decline. Education and plasma homocysteine levels modulated age-related decline in cognitive performance. Total cerebral volume declined at an annual rate of 0.4%/yr. Gray and white matter volume loss was comparable in magnitude. Regionally, there was relatively greater volume loss in the lateral prefrontal cortex bilaterally, around the primary visual cortex as well as bilateral superior parietal cortices. Speed of processing showed significant positive correlation with gray matter volume in several frontal, parietal and midline occipital regions bilaterally. In spite of differences in diet, lifestyle and culture, these findings are broadly comparable to studies conducted in Caucasian populations and suggest generalizability of processes involved in age-related decline in cognition and brain volume.

Aging and loss decision making: increased risk aversion and decreased use of maximizing information, with correlated rationality and value maximization.

We investigated how adult aging specifically alters economic decision-making, focusing on examining alterations in uncertainty preferences (willingness to gamble) and choice strategies (what gamble information influences choices) within both the gains and losses domains. Within each domain, participants chose between certain monetary outcomes and gambles with uncertain outcomes. We examined preferences by quantifying how uncertainty modulates choice behavior as if altering the subjective valuation of gambles. We explored age-related preferences for two types of uncertainty, risk, and ambiguity. Additionally, we explored how aging may alter what information participants utilize to make their choices by comparing the relative utilization of maximizing and satisficing information types through a choice strategy metric. Maximizing information was the ratio of the expected value of the two options, while satisficing information was the probability of winning. We found age-related alterations of economic preferences within the losses domain, but no alterations within the gains domain. Older adults (OA; 61-80 years old) were significantly more uncertainty averse for both risky and ambiguous choices. OA also exhibited choice strategies with decreased use of maximizing information. Within OA, we found a significant correlation between risk preferences and choice strategy. This linkage between preferences and strategy appears to derive from a convergence to risk neutrality driven by greater use of the effortful maximizing strategy. As utility maximization and value maximization intersect at risk neutrality, this result suggests that OA are exhibiting a relationship between enhanced rationality and enhanced value maximization. While there was variability in economic decision-making measures within OA, these individual differences were unrelated to variability within examined measures of cognitive ability. Our results demonstrate that aging alters economic decision-making for losses through changes in both individual preferences and the strategies individuals employ.

Sleep reduces false memory in healthy older adults.

STUDY OBJECTIVES: To investigate the effects of post-learning sleep and sleep architecture on false memory in healthy older adults. DESIGN: Balanced, crossover design. False memory was induced using the Deese-Roediger-McDermott (DRM) paradigm and assessed following nocturnal sleep and following a period of daytime wakefulness. Post-learning sleep structure was evaluated using polysomnography (PSG). SETTING: Sleep research laboratory. PARTICIPANTS: Fourteen healthy older adults from the Singapore-Longitudinal Aging Brain Study (mean age ± standard deviation = 66.6 ± 4.1 y; 7 males). MEASUREMENTS AND RESULTS: At encoding, participants studied lists of words that were semantically related to non-presented critical lures. At retrieval, they made "remember"/"know" and "new" judgments. Compared to wakefulness, post-learning sleep was associated with reduced "remember" responses, but not "know" responses to critical lures. In contrast, there were no significant differences in the veridical recognition of studied words, false recognition of unrelated distractors, discriminability, or response bias between the sleep and the wake conditions. More post-learning slow wave sleep was associated with greater reduction in false memory. CONCLUSIONS: In healthy older adults, sleep facilitates the reduction in false memory without affecting veridical memory. This benefit correlates with the amount of slow wave sleep in the post-learning sleep episode.

Sleep duration and age-related changes in brain structure and cognitive performance.

STUDY OBJECTIVES: To investigate the contribution of sleep duration and quality to age-related changes in brain structure and cognitive performance in relatively healthy older adults. DESIGN: Community-based longitudinal brain and cognitive aging study using a convenience sample. SETTING: Participants were studied in a research laboratory. PARTICIPANTS: Relatively healthy adults aged 55 y and older at study commencement. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Participants underwent magnetic resonance imaging and neuropsychological assessment every 2 y. Subjective assessments of sleep duration and quality and blood samples were obtained. Each hour of reduced sleep duration at baseline augmented the annual expansion rate of the ventricles by 0.59% (P = 0.007) and the annual decline rate in global cognitive performance by 0.67% (P = 0.050) in the subsequent 2 y after controlling for the effects of age, sex, education, and body mass index. In contrast, global sleep quality at baseline did not modulate either brain or cognitive aging. High-sensitivity C-reactive protein, a marker of systemic inflammation, showed no correlation with baseline sleep duration, brain structure, or cognitive performance. CONCLUSIONS: In healthy older adults, short sleep duration is associated with greater age-related brain atrophy and cognitive decline. These associations are not associated with elevated inflammatory responses among short sleepers. CITATION: Lo JC, Loh KK, Zheng H, Sim SK, Chee MW. Sleep duration and age-related changes in brain structure and cognitive performance.

Culture-related differences in default network activity during visuo-spatial judgments.

Studies on culture-related differences in cognition have shown that Westerners attend more to object-related information, whereas East Asians attend more to contextual information. Neural correlates of these different culture-related visual processing styles have been reported in the ventral-visual and fronto-parietal regions. We conducted an fMRI study of East Asians and Westerners on a visuospatial judgment task that involved relative, contextual judgments, which are typically more challenging for Westerners. Participants judged the relative distances between a dot and a line in visual stimuli during task blocks and alternated finger presses during control blocks. Behaviorally, East Asians responded faster than Westerners, reflecting greater ease of the task for East Asians. In response to the greater task difficulty, Westerners showed greater neural engagement compared to East Asians in frontal, parietal, and occipital areas. Moreover, Westerners also showed greater suppression of the default network-a brain network that is suppressed under condition of high cognitive challenge. This study demonstrates for the first time that cultural differences in visual attention during a cognitive task are manifested both by differences in activation in fronto-parietal regions as well as suppression in default regions.

Culture differences in neural processing of faces and houses in the ventral visual cortex.

Behavioral and eye-tracking studies on cultural differences have found that while Westerners have a bias for analytic processing and attend more to face features, East Asians are more holistic and attend more to contextual scenes. In this neuroimaging study, we hypothesized that these culturally different visual processing styles would be associated with cultural differences in the selective activity of the fusiform regions for faces, and the parahippocampal and lingual regions for contextual stimuli. East Asians and Westerners passively viewed face and house stimuli during an functional magnetic resonance imaging experiment. As expected, we observed more selectivity for faces in Westerners in the left fusiform face area (FFA) reflecting a more analytic processing style. Additionally, Westerners showed bilateral activity to faces in the FFA whereas East Asians showed more right lateralization. In contrast, no cultural differences were detected in the parahippocampal place area (PPA), although there was a trend for East Asians to show greater house selectivity than Westerners in the lingual landmark area, consistent with more holistic processing in East Asians. These findings demonstrate group biases in Westerners and East Asians that operate on perceptual processing in the brain and are consistent with previous eye-tracking data that show cultural biases to faces.