Memory Binding Test and Its Associations With Hippocampal Volume Across the Cognitive Continuum Preceding Dementia

Innovative memory paradigms have been introduced to capture subtle memory changes in early Alzheimer’s disease (AD). We aimed to examine the associations between different indexes of the challenging Memory Binding Test (MBT) and hippocampal volume (HV) in a sample of individuals with subjective cognitive decline (SCD; n = 50), amnestic mild cognitive impairment (aMCI) due to AD ( n = 31), and cognitively normal (CN) older adults ( n = 29) recruited from the Czech Brain Aging Study, in contrast to traditional verbal memory tests. Both MBT free and cued recall scores in immediate and delayed recall conditions were associated with lower HV in both SCD and aMCI due to AD, whereas in traditional verbal memory tests only delayed recall scores were associated with lower HV. In SCD, the associations with lower HV in the immediate recall covered specific cued recall indexes only. In conclusion, the MBT is a promising test for detecting subtle hippocampal-associated memory decline during the predementia continuum.

Variability in Cognitive Performance on Mobile Devices Is Sensitive to Mild Cognitive Impairment: Results From the Einstein Aging Study

Background and Objective: Within-person variability in cognitive performance has emerged as a promising indicator of cognitive health with potential to distinguish normative and pathological cognitive aging. We use a smartphone-based digital health approach with ecological momentary assessments (EMA) to examine differences in variability in performance among older adults with mild cognitive impairment (MCI) and those who were cognitively unimpaired (CU).Method: A sample of 311 systematically recruited, community-dwelling older adults from the Einstein Aging Study (Mean age = 77.46 years, SD = 4.86, Range = 70–90; 67% Female; 45% Non-Hispanic White, 40% Non-Hispanic Black) completed neuropsychological testing, neurological assessments, and self-reported questionnaires. One hundred individuals met Jak/Bondi criteria for MCI. All participants performed mobile cognitive tests of processing speed, visual short-term memory binding, and spatial working memory on a smartphone device up to six times daily for 16 days, yielding up to 96 assessments per person. We employed heterogeneous variance multilevel models using log-linear prediction of residual variance to simultaneously assess cognitive status differences in mean performance, within-day variability, and day-to-day variability. We further tested whether these differences were robust to the influence of environmental contexts under which assessments were performed.Results: Individuals with MCI exhibited greater within-day variability than those who were CU on ambulatory assessments that measure processing speed (p < 0.001) and visual short-term memory binding (p < 0.001) performance but not spatial working memory. Cognitive status differences in day-to-day variability were present only for the measure of processing speed. Associations between cognitive status and within-day variability in performance were robust to adjustment for sociodemographic and contextual variables.Conclusion: Our smartphone-based digital health approach facilitates the ambulatory assessment of cognitive performance in older adults and the capacity to differentiate individuals with MCI from those who were CU. Results suggest variability in mobile cognitive performance is sensitive to MCI and exhibits dissociative patterns by timescale and cognitive domain. Variability in processing speed and visual short-term memory binding performance may provide specific detection of MCI. The 16-day smartphone-based EMA measurement burst offers novel opportunity to leverage digital technology to measure performance variability across frequent assessments for studying cognitive health and identifying early clinical manifestations of cognitive impairment.

Oculomotor Behaviors and Integrative Memory Functions in the Alzheimer’s Clinical Syndrome

Background: Biological information drawn from eye-tracking metrics is providing evidence regarding drivers of cognitive decline in Alzheimer’s disease. In particular, pupil size has proved useful to investigate cognitive performance during online activities. Objective: To investigate the oculomotor correlates of impaired performance of patients with mild Alzheimer’s Clinical Syndrome (ACS) on a recently developed memory paradigm, namely the Short-Term Memory Binding Test (STMBT). Methods: We assessed a sample of eighteen healthy controls (HC) and eighteen patients with a diagnosis of mild ACS with the STMBT while we recorded their oculomotor behaviors using pupillometry and eye-tracking. Results: As expected, a group (healthy controls versus ACS) by condition (Unbound Colours versus Bound Colours) interaction was found whereby behavioral group differences were paramount in the Bound Colours condition. Healthy controls’ pupils dilated significantly more in the Bound Colours than in the Unbound Colours condition, a discrepancy not observed in ACS patients. Furthermore, ROC analysis revealed the abnormal pupil behaviors distinguished ACS patients from healthy controls with values of sensitivity and specify of 100%, thus outperforming both recognition scores and gaze duration. Conclusion: The biological correlates of Short-Term Memory Binding impairments appear to involve a network much wider than we have thought to date, which expands across cortical and subcortical structures. We discuss these findings focusing on their implications for our understanding of neurocognitive phenotypes in the preclinical stages of Alzheimer’s disease and potential development of cognitive biomarkers that can support ongoing initiatives to prevent dementia.

High-performance adaptive texture streaming and rendering of large 3D cities

We propose a high-performance texture streaming system for real-time rendering of large 3D cities with millions of textures. Our main contribution is a texture streaming system that automatically adjusts the streaming workload at runtime based on measured frame latencies, specifically addressing the high memory binding costs of hardware virtual texturing which causes frame rate stuttering. Our system streams textures in parallel with prioritization based on GPU computed mesh perceptibility, and these textures are cached in a sparse partially resident image at runtime without the need for a texture preprocessing step. In addition, we improve rendering quality by minimizing texture pop-in artifacts using a color blending scheme based on mipmap levels. We evaluate our texture streaming system using three structurally distinct datasets with many textures and compared it to a baseline, a game engine, and our prior method. Results show an 8X improvement in rendering performance and 7X improvement in rendering quality compared to the baseline.

174 Discrimination moderates the association of sleep and cognitive function in older Black adults: The Einstein Aging Study

Introduction Experiences of discrimination attributed to a range of individual characteristics (race, skin color, age, sex, etc.) may influence the extent to which sleep impacts cognitive functioning in order adults, particularly within older minorities. Thus, we investigated the effect of discrimination on the relationship between actigraphic sleep quality and cognitive function in analyses stratified by race. Methods Participants (N=286, mean age=77.4 years, 32% males; 45% white, 41% Black, 14% Hispanic/others) enrolled in The Einstein Aging Study were included. Sleep disturbance, as measured by wake after sleep onset (WASO) (mean=63 min, sd=27 min), was calculated from wrist actigraphy over 15.4±1.4 days. Participants’ mean ambulatory cognitive function was assessed with a validated, memory binding, smartphone-based EMA task (Color Shapes) repeated 4 times daily. A modified version of the Williams’ Everyday Discrimination questionnaire, optimized for older adults, measured participants’ endorsement of discriminated characteristics. Linear regressions, stratified by race (white, Black separately), were conducted with interaction terms to investigate whether discrimination moderated associations between WASO and ambulatory cognitive function. Models controlled for age, education, income, and gender. Regions of significance were also evaluated. Results Race-stratified analysis indicated that the association between mean WASO and cognitive function was significantly moderated by the number of discriminated characteristics among Black adults (n=117), not whites (n=128). Specifically, among Black adults who identified few discriminated characteristics, WASO was not significantly associated with memory binding. However, Black adults who identified discriminated characteristics at +1 SD above the mean (5.5 traits) exhibited a 12% lower average memory binding test score (percent responses correct) with each half-hour greater mean WASO (p=.01). Analysis of the region of significance showed the association is significant when participants endorsed more than three discriminated characteristics. Conclusion These findings emphasize the importance of considering sociocultural factors, such as discrimination, to understand the association between sleep quality and cognitive functioning, particularly for older Blacks. Support (if any) R01AG062622

Optimizing Subjective Cognitive Decline to Detect Early Cognitive Dysfunction

Background: The utility of subjective cognitive decline (SCD) as an indicator of preclinical AD is overshadowed by its inconsistent association with objective cognition. Objective: This study examines if manipulations of SCD measurement affect its association with early cognitive dysfunction characteristic of preclinical AD. Methods: Cognitively healthy older adults (n = 110) completed SCD questionnaires that elicited complaints in general, compared to 5 years ago (retrospective SCD) and compared to their peers (age-anchored SCD) in binary and Likert scales. Outcome cognitive tasks included an associative memory task (Face-Name Test), a visual short-term memory binding task (STMB test), and a clinical neuropsychological list learning test (Selective Reminder Test). Results: SCD complaints, when compared to age-matched peers (age-anchored SCD) were endorsed less frequently than complaints compared to 5 years ago (retrospective SCD) (p < 0.01). In demographically adjusted regressions, age-anchored ordinal-rated SCD was associated with short term memory binding (β= –0.22, p = 0.040, CI = –0.45, –0.01), associative memory (β= –0.26, p = 0.018, CI = –0.45, –0.06), and list learning (β= –0.31, p = 0.002, CI = –0.51, –0.12). Retrospective and general ordinal-rated SCD was associated with associative memory (β= –0.25, p = 0.012, CI = –0.44, –0.06; β= –0.29, p = 0.003, CI = –0.47, –0.10) and list learning only (β= –0.25, p = 0.014, CI = –0.45, –0.05; β= –0.28, p = 0.004, CI = –0.48, –0.09). Conclusion: Ordinal age-anchored SCD appears better suited than other SCD measurements to detect early cognitive dysfunction characteristic of preclinical AD.