Selective attention in early Dementia of Alzheimer Type

Attentional network changes in subjective cognitive decline

BACKGROUND

Subjective cognitive decline (SCD) is known as the intermediate stage between normal cognitive aging and mild cognitive impairment (MCI). Although elderly with SCD usually perform close to normal in standardized tests, the detailed function of attention networks in this group has not been studied yet.

AIMS

The purpose of this study was to investigate the performance of attention networks, as a possible indicator of cognitive disorder, in older individuals with subjective memory complaint and MCI.

METHOD

The attention network test (ANT) was used to examine and compare the performance of three attention networks of alerting, orientation, and executive control in 17 elderly with SCD, 30 multiple domain amnestic MCI subjects, and 15 healthy controls.

RESULTS

Although the orienting network had almost the same performance in all groups (p = 0.25), the performance of alerting (p = 0.01) and executive control networks (p = 0.02) were significantly different among the three groups: the SCD group performed poorly in both networks compared with the controls and did not differ significantly from the MCI group (p ≥ 0.05). However, controlling for general age-related slowing abolished the group difference in executive control index. More importantly, our results showed that alerting network that was affected in SCD group had high sensitivity in differentiating this group from controls (0.94%).

CONCLUSION

Our data suggest that despite normal performance in neuropsychological tests, the SCD elderly may face significant degrees of attention processing problems, especially in maintaining alerting to external stimuli which might be helpful in diagnosing individuals at risk and designing proper attention-based interventions.

Sensor-based fall risk assessment in older adults with or without cognitive impairment: a systematic review

BACKGROUND

Higher age and cognitive impairment are associated with a higher risk of falling. Wearable sensor technology may be useful in objectively assessing motor fall risk factors to improve physical exercise interventions for fall prevention. This systematic review aims at providing an updated overview of the current research on wearable sensors for fall risk assessment in older adults with or without cognitive impairment. Therefore, we addressed two specific research questions: 1) Can wearable sensors provide accurate data on motor performance that may be used to assess risk of falling, e.g., by distinguishing between faller and non-faller in a sample of older adults with or without cognitive impairment?; and 2) Which practical recommendations can be given for the application of sensor-based fall risk assessment in individuals with CI? A systematic literature search (July 2019, update July 2020) was conducted using PubMed, Scopus and Web of Science databases. Community-based studies or studies conducted in a geriatric setting that examine fall risk factors in older adults (aged ≥60 years) with or without cognitive impairment were included. Predefined inclusion criteria yielded 16 cross-sectional, 10 prospective and 2 studies with a mixed design.

RESULTS

Overall, sensor-based data was mainly collected during walking tests in a lab setting. The main sensor location was the lower back to provide wearing comfort and avoid disturbance of participants. The most accurate fall risk classification model included data from sit-to-walk and walk-to-sit transitions collected over three days of daily life (mean accuracy = 88.0%). Nine out of 28 included studies revealed information about sensor use in older adults with possible cognitive impairment, but classification models performed slightly worse than those for older adults without cognitive impairment (mean accuracy = 79.0%).

CONCLUSION

Fall risk assessment using wearable sensors is feasible in older adults regardless of their cognitive status. Accuracy may vary depending on sensor location, sensor attachment and type of assessment chosen for the recording of sensor data. More research on the use of sensors for objective fall risk assessment in older adults is needed, particularly in older adults with cognitive impairment.

TRIAL REGISTRATION

This systematic review is registered in PROSPERO ( CRD42020171118 ).

Age Differences in the Subcomponents of Executive Functioning

OBJECTIVES

Across the life span, deficits in executive functioning (EF) are associated with poor behavioral control and failure to achieve goals. Though EF is often discussed as one broad construct, a prominent model of EF suggests that it is composed of three subdomains: inhibition, set shifting, and updating. These subdomains are seen in both younger (YA) and older adults (OA), with performance deficits across subdomains in OA. Therefore, our goal was to investigate whether subdomains of EF might be differentially affected by age, and how these differences may relate to broader global age differences in EF.

METHODS

To assess these age differences, we conducted a meta-analysis at multiple levels, including task level, subdomain level, and of global EF. Based on previous work, we hypothesized that there would be overall differences in EF in OA.

RESULTS

Using 1,268 effect sizes from 401 articles, we found overall differences in EF with age. Results suggested that differences in performance are not uniform, such that variability in age effects emerged at the task level, and updating was not as affected by age as other subdomains.

DISCUSSION

These findings advance our understanding of age differences in EF, and stand to inform early detection of EF decline.

Art Training in Dementia: A Randomized Controlled Trial

Objectives

The present study explores the effect of visual art training on people with dementia, utilizing a randomized control trial design, in order to investigate the effects of an 8-week visual art training program on cognition. In particular, the study examines overall cognition, delayed recall, and working memory, which show deficits in people with dementia.

Method

Fifty-three individuals with dementia were randomly assigned into either an art training (n = 27) or usual-activity waitlist control group (n = 26). Overall cognition and delayed recall were assessed with the Montreal Cognitive Assessment (MoCA), and working memory was assessed with the Backward Digit Span task.

Results

There were no group differences in overall cognition, or working memory, while a difference in delayed recall was undetermined, based on post-test—pre-test difference scores. Groups were comparable at baseline on all measures.

Conclusion

The measures of cognition, delayed recall, and working memory used in this study were not affected by an 8-week visual art training program.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT03175822.

Journey of ethics - Conducting collaborative research with people with dementia

This paper explores some of the ethical considerations of working collaboratively with people with dementia within research based upon the experiences, challenges and learning from three doctoral research studies. Focus is on the research relationship with participants and gatekeepers, the importance of setting and access, the power relations within the research and ways in which people with dementia can be supported to be active and have a voice in research. This sits within an ethical framework of principalist ethics and ethics of care to guide not only how research is planned ethically and with consideration of participants, but also how this can support decisions made in situ. The aim is to share, based upon these three studies, ways of managing and working through some of the ethical consideration to support researchers in their decisions in planning and conducting research with people with dementia as active collaborators.

Subjective cognitive impairment: Functional MRI during a divided attention task

Background

Individuals with subjective cognitive impairment (SCI) have persistent memory complaints but normal neurocognitive performance. For some, this may represent a pre-mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). Given that attentional deficits and associated brain activation changes are present early in the course of AD, we aimed to determine whether SCI is associated with brain activation changes during attentional processing.

Methods

Eleven SCI subjects and 10 controls completed a divided attention task during functional magnetic resonance imaging.

Results

SCI and control groups did not differ in sociodemographic, neurocognitive or behavioural measures. When group activation during the divided attention task was compared, the SCI group demonstrated increased activation in left medial temporal lobe, bilateral thalamus, posterior cingulate and caudate.

Conclusion

This pattern of increased activation is similar to the pattern of decreased activation reported during divided attention in AD and may indicate compensatory changes. These findings suggest the presence of early functional changes in SCI; longitudinal studies will help to further elucidate the relationship between SCI and AD.

Home-based evaluation of executive function (Home-MET) for older adults with mild cognitive impairment

INTRODUCTION

Executive function helps older adults maintain their activities of daily living by making plans, setting goals, and carrying them out successfully. It is important for their independence in community living.

METHODS

With a carefully match-group of 80 mild cognitive impaired with 80 health control subjects. The home-based evaluation of executive function (Home-MET) was validated in subjects' own living environment.

RESULTS

This Home-MET showed significant correlation in the assessment of attention control that was assessing by Test of Everyday Attention (TEA) (r = .86, p < .01), with working memory that was assessed with Trail Making Test (TMT) (r = .72, p < .01), with inhibitory control that was assessing with Stroop Test (r = .86, p < .01), with individuals' functional disability was assessed by Chinese Disability Assessment of Dementia (CDAD) (r = .77, p < .01) and cognitive assessment was assessed by Hong Kong Montreal Cognitive Assessment (HK-MoCA) (r = .88, p < .01). By benchmarking with the validated performance-based executive function assessment, the Home-MET shows significant correlation (r = .92, p < .05) with the executive function test in a standard environment in hospital, i.e. the Chinese Multiple Errands Test (the Chinese-MET). The two-stage hierarchical linear regression model with backward method showed functional disability was a marginally significant predictor (p < .059) for the Home-MET with regression model showed with R² = .93.

CONCLUSION

Results indicated the Home-MET, can provide an objective measure of executive function for subjects with mild cognitive impairment in participants' own home environment.

Alzheimer's Disease: Prototype of Cognitive Deterioration, Valuable Lessons to Understand Human Cognition

It is important for neurologists to become more familiar with neuropsychological evaluation for Alzheimer disease. The growth of this method in research, as an available, inexpensive, and noninvasive diagnostic approach, which can be administered even by non-specialist-trained examiners, makes this knowledge more necessary than ever. Such knowledge has a basic role in planning national programs in primary health care systems for prevention and early detection of Alzheimer disease. This is more crucial in developing countries, which have higher rates of dementia prevalence along with cardiovascular risk factors, lack of public knowledge about dementia, and limited social support. In addition compared to the neurological hard signs which are tangible and measurable, the concept of cognition seems to be more difficult for the neurologists to evaluate and for the students to understand. Dementia in general and Alzheimer's disease as the prototype of cognitive disorders specifically, play an important role to explore all domains of human cognition through its symptomatology and neuropsychological deficits.

Attention-related networks in Alzheimer's disease: a resting functional MRI study

In addition to memory deficits, attentional impairment is a common manifestation of Alzheimer's disease (AD). The present study examines the abnormalities of attention-related functional networks in AD using resting functional MRI (fMRI) technique and evaluates the sensitivity and specificity of these networks as potential biomarkers compared with the default mode network (DMN). Group independent component analysis (Group ICA) was applied to fMRI data from 15 AD patients and 16 normal healthy elderly controls (NC) to derive the dorsal attention network (DAN) and the ventral attention network (VAN) which are respectively responsible for the endogenous attention orienting ("top-down") process and the exogenous attention re-orienting ("bottom-up") process. Receiver operating characteristic (ROC) curve analysis was performed for activity in core regions within each of these networks. Functional connectivity analysis revealed disrupted DAN and preserved (less impaired) VAN in AD patients compared with NC, which might indicate impairment of a "top-down" and intact "bottom-up" attentional processing mechanisms in AD. ROC curve analysis suggested that activity in the left intraparietal sulcus and left frontal eye field from DAN as well as the posterior cingulate cortex from the DMN could serve as sensitive and specific biomarkers distinguishing AD from NC.

Abnormal temporal dynamics of visual attention in Alzheimer's disease and in dementia with Lewy bodies

Although attentional control processes are disproportionately impaired in dementia with Lewy bodies (DLB) compared with dementia of the Alzheimer type (DAT), previous studies have not compared directly the temporal dynamics of visual attention in DLB and DAT. We examined the magnitude of the attentional blink (AB) effect in these patients, to determine the degree to which each patient group exhibited a deficit in selecting and processing visual stimuli presented in rapid succession. Eighteen DAT, 15 DLB patients, and 33 elderly controls were tested in a rapid serial visual presentation task. Participants were asked to report 1 (single-target condition) or 2 target letters (dual-target condition) embedded in a sequence of digit distracters. The temporal dynamics of visual attention was examined by varying the number of intervening distracters between the 2 targets in the dual-target condition and by estimating the attentional blink effect as the decline in the ability to report the second target correctly after successfully identifying the first. Patients with DLB performed significantly worse than patients with DAT and controls in both the single and dual-targets conditions. In contrast, DAT patients showed a selective impairment in the dual-target condition as compared with controls. As predicted, we found that both patients with DAT and DLB showed a more pronounced and protracted attentional blink than controls, indicating a reduced ability to re-engage attention on the second target. Furthermore, when DAT and DLB patients were able to report the second target, they frequently failed to identify the first, an effect that was absent in elderly controls and particularly large and long-lasting in DLB patients. This study suggests that both DLB and DAT patients show abnormal temporal dynamics of visual selective attention, presumably due to a greater intertarget competition for limited processing capacity. More generally, these findings reinforce the notion that deficits of attentional control processes are more severe in DLB patients as compared with DAT patients.

Reliable change indices for the ruff 2 and 7 selective attention test in older adults

The assessment of suspected dementia often involves the analysis of change scores from neuropsychological tests administered on two occasions. Frequently, no information is available to allow the significance of a change to be evaluated. Our aim was to prepare data useful for estimating the statistical significance of retest changes for persons older than the age of 65 on the Ruff 2 and 7 Selective Attention Test, one of the few paper-and-pencil tests of attention available to the clinician. The sample tested was composed of 234 healthy adults taking part in a randomized double-blind trial of the effect on cognitive performance of lowering homocysteine using dietary supplements, during which no treatment effects were detected. The test was found to be sensitive to the effects of aging and was well tolerated by our sample of older adults. Retest reliability for the speed of visual search for digit targets (2 and 7) under both the same category (other digits) and different category (letter) distracter conditions was high, and the practice effects during a 12-month period were substantial. Test-retest data with a 1-year interval were used to estimate reliability coefficients and to calculate Reliable Change indices useful for evaluating persons with suspected dementia. The rate of decline in search speed as a function of age was the same for both distraction conditions, suggesting that older persons used a controlled serial search process for targets in both conditions of this test.

Application of attention network test and demographic information to detect mild cognitive impairment via combining feature selection with support vector machine

Mild cognitive impairment (MCI) is now thought as the prodromal phase of Alzheimer's disease (AD), and the usual method for diagnosing the disease would be a battery of neuropsychological assessment. The present study proposes to integrate a feature selection scheme with support vector machine (SVM) to identify patients with MCI by using attention network test (ANT) and demographic data. Forty-two patients with MCI and forty-five normal individuals underwent ANT recording, and the reaction time and accuracy of ANT and demographics (age, gender, and educational level) were selected as original features. To select features, we first introduced some random variables as probe features in the original data, then ranked all the features according to their influence on the support vector machine decision function, and finally selected those features that had an influence higher than that of the probes. Initially 18 different features were reduced to only four features by our method. SVM classifier created by using these four features gave an 85% classification accuracy with a sensitivity of 85% and a specificity of 86%. And the area under the curve obtained by receiver operating characteristics analysis was 0.918. The experimental results demonstrate that the proposed method is a good potential use to assist identifying patients with MCI objectively and efficiently.