Force-fluctuations during role-differentiated bimanual movements reflect cognitive impairments in older adults. A cohort sequential study.

During role-differentiated bimanual movements (RDBM), an object is typically stabilized with one hand and manipulated with the other. RDBM require coupling both hands for coordinated action (achieved through interhemispheric connections), but also inhibition of crosstalk to avoid involuntary movements in the stabilizing hand. We investigated how healthy cognitive aging and mild cognitive impairments (MCI) affect force-stabilization during an RDBM in a cohort sequential study design with up to 4 measurement points over 32 months. 132 older adults (>80 years) participated in this study, 77 were cognitively healthy individuals (CHI) and 55 presented with MCI. Participants performed a visuomotor bimanual force-tracking task. They either produced a constant force with both hands (bimanual constant) or a constant force with one and an alternating force with the other hand (role-differentiated). We investigated force-fluctuations of constant force-production using the coefficient of variation (CV), detrended fluctuation analysis (DFA) and sample entropy (SEn). Results showed higher CV and less complex variability structure (higher DFA and lower SEn) during the role-differentiated compared to the bimanual constant task. Furthermore, CHI displayed a more complex variability structure during the bimanual constant, but a less complex structure during the role-differentiated task than MCI. Interestingly this complexity reduction was more pronounced in CHI than MCI individuals, suggesting different changes in the control mechanisms. While understanding these changes requires further research, potential causes might be structural deteriorations leading to less efficient (intra- and interhemispheric) networks because of MCI, or an inability to appropriately divert the focus of attention.

Cardiorespiratory fitness is associated with cognitive performance in 80 + -year-olds: Detangling processing levels.

Cardiorespiratory fitness is known to protect against cognitive decline in older adults. Specifically, it has been shown that physical activity and fitness are beneficial for executive functions that are crucial for independent living up to old age. In this study, 115 individuals aged 80 years and older underwent a cardiorespiratory fitness assessment using the two-minute step test and had their electroencephalogram recorded during a colored flanker task in order to measure executive function performance. Cardiorespiratory fitness was related to quicker responses during the flanker task. A mediation analysis was carried out to determine whether these positive effects were mediated through event-related potentials (N1, N2, or P3) or motor-related cortical potentials (MRCP). Cardiorespiratory fitness was related to better visual discriminative processing as indicated by larger occipital N1 amplitudes. In addition, fitness was associated with larger MRCP amplitudes, which are a correlate of the response generation process. Fitness was not found to have a significant effect on fronto-central N2 or parietal P3, which are thought to capture cognitive control processes such as conflict detection and response inhibition. Moreover, all effects reported were present in all three flanker trial conditions (congruent, neutral, and incongruent). Thus, these results indicate that the quicker response times in fitter people were related to visual processing and motor response generation rather than cognitive control.

Sex-dependent performance differences in curvilinear aiming arm movements in octogenarians.

In an aging society, it is necessary to detect the cognitive decline of individuals at an early stage using simple measurement methods. This makes early health care possible for those affected. The aim of the study was to develop a classifier for cognitive state in older adults with and without mild cognitive impairment (MCI) based on kinematic parameters of linear and curvilinear aiming arm movements. In a group of 224 older adults over 80 years of age (cognitively healthy and MCI), the movement duration and intersegment intervals of linear and curvilinear arm movements of 20 cm were recorded. Movement duration was significantly longer in the curvilinear condition than in the straight movement, and MCI participants required significantly more time than cognitively healthy participants. Post-hoc analysis on the fluidity of movement in the curvilinear condition showed that MCI men had significantly longer inter-segmental intervals than non-MCI men. No difference was found in women. Based on the inter-segmental intervals, a simple classifier could be developed that correctly classified 63% of the men. In summary, aiming arm movements are only conditionally suitable as a classifier for cognitive states. For the construction of an ideal classifier, age-related degeneration of cortical and subcortical motor areas should be considered.

Bimanual coupling is associated with left frontocentral network activity in a task-specific way.

When performing bimanual tasks, hands are typically not controlled individually but rather as a coupled system to achieve high spatiotemporal coordination. On a brain level, intrahemispheric and interhemispheric networks that control the left and right hand are necessary to exchange information between hemispheres and to couple movements. Behaviourally, coupling is, however, highly task-specific requiring, for example, to maintain a specific relative phase in cyclic tasks (e.g., inphase or antiphase) or to perform a role differentiated task where one hand is modulating and the other hands is stabilizing and needs to be kept as still as possible (e.g., holding a notepad and writing on it). In this study, we used electroencephalography to investigate functional brain network characteristics (task-related activation and connectivity) in bimanual force-control tasks with different coordination modes: inphase, antiphase and role-differentiated with the left- or right-hand stabilizing and the other hand manipulating. We aimed to examine (1) how network characteristics differ with respect to the coordination mode and (2) how they are related to the performance. Results revealed task-related differences in the overall activation and connectivity with role-differentiated tasks leading to higher desynchronization as compared to inphase and antiphase tasks. In addition, we showed that the strength of bimanual coupling is modulated task specifically through left-hemispheric networks including C3, FC3 and F3 electrodes. Results highlight the importance of the left frontocentral regions for bimanual coordination.

Classification of age groups and task conditions provides additional evidence for differences in electrophysiological correlates of inhibitory control across the lifespan.

The aim of this study was to extend previous findings on selective attention over a lifetime using machine learning procedures. By decoding group membership and stimulus type, we aimed to study differences in the neural representation of inhibitory control across age groups at a single-trial level. We re-analyzed data from 211 subjects from six age groups between 8 and 83 years of age. Based on single-trial EEG recordings during a flanker task, we used support vector machines to predict the age group as well as to determine the presented stimulus type (i.e., congruent, or incongruent stimulus). The classification of group membership was highly above chance level (accuracy: 55%, chance level: 17%). Early EEG responses were found to play an important role, and a grouped pattern of classification performance emerged corresponding to age structure. There was a clear cluster of individuals after retirement, i.e., misclassifications mostly occurred within this cluster. The stimulus type could be classified above chance level in ~ 95% of subjects. We identified time windows relevant for classification performance that are discussed in the context of early visual attention and conflict processing. In children and older adults, a high variability and latency of these time windows were found. We were able to demonstrate differences in neuronal dynamics at the level of individual trials. Our analysis was sensitive to mapping gross changes, e.g., at retirement age, and to differentiating components of visual attention across age groups, adding value for the diagnosis of cognitive status across the lifespan. Overall, the results highlight the use of machine learning in the study of brain activity over a lifetime.

Finger Tapping as a Biomarker to Classify Cognitive Status in 80+-Year-Olds.

This study examined the association between finger tapping and cognitive function in a group of 225 elderly participants (116 males; age 79-92 years; M = 82.5; SD = 2.4). Finger tapping was assessed in two conditions: self-selected pace and fast pace. Based on cognitive assessments, including the MoCA and CERA-NP test battery, participants were classified as cognitively healthy individuals (CHI), participants with mild cognitive impairments (MCI), and those with possible MCI (pMCI). Results of the analyses show significant differences between groups, sex and the group × sex interaction in four parameters for the self-selected pace condition and eight parameters for the fast pace condition. These parameters were used for classification by means of linear discriminant analysis (LDA). The first LDA component showed significant differences between CHI and pMCI and between CHI and MCI. Furthermore, the second LDA component showed significant differences between CHI and pMCI as well as between pMCI and MCI. Nevertheless, the algorithm correctly classified only 50% of participants, regardless of group, suggesting that tapping parameters are only partially useful for classification in early stages of dementia. We discuss these findings in terms of the diadochokinetic nature of finger tapping as associated with the age-related degeneration of cortical and subcortical motor areas.

Normative Data for the CERAD-NP for Healthy High-Agers (80-84 years) and Effects of Age-Typical Visual Impairment and Hearing Loss.

OBJECTIVES: This study aims to establish reference data for nondemented adults between 80 and 84 years of age based on the German version of the Consortium to Establish a Registry for Alzheimer's disease Neuropsychological (CERAD-NP) test battery and to assess the possible influence of hearing and vision impairments on CERAD-NP performance. METHODS: Two hundred one volunteers were examined with the German CERAD-NP test battery, and 18 test scores were calculated from the data. The sample included 99 men (49%), the mean age was 81.8 years (SD = 1.3), and the mean years of education were 13.9 (SD = 3.1). Percentiles for continuous and percentile ranks for discrete test scores were calculated separately for four norm groups. The groups were classified according to gender and education. Multiple regression analysis was used to predict cognitive performance from visual acuity and hearing ability. RESULTS: The normative data obtained were consistent with other findings from younger and older age groups. Worse visual acuity predicted slower performance in the Trail Making Test (TMT). None of the other CERAD-NP tests were correlated to sensory functions. CONCLUSIONS: Using age-appropriate reference data, such as that established here for the 80-84 year age group can help to improve the detection of cognitive decline and prevent biases that arise when old-old adults are compared to younger old adults. Visual acuity should be considered an influencing factor on TMT performance.

Characteristics of Resting State EEG Power in 80+-Year-Olds of Different Cognitive Status.

Compared with healthy older adults, patients with Alzheimer's disease show decreased alpha and beta power as well as increased delta and theta power during resting state electroencephalography (rsEEG). Findings for mild cognitive impairment (MCI), a stage of increased risk of conversion to dementia, are less conclusive. Cognitive status of 213 non-demented high-agers (mean age, 82.5 years) was classified according to a neuropsychological screening and a cognitive test battery. RsEEG was measured with eyes closed and open, and absolute power in delta, theta, alpha, and beta bands were calculated for nine regions. Results indicate no rsEEG power differences between healthy individuals and those with MCI. There were also no differences present between groups in EEG reactivity, the change in power from eyes closed to eyes open, or the topographical pattern of each frequency band. Overall, EEG reactivity was preserved in 80+-year-olds without dementia, and topographical patterns were described for each frequency band. The application of rsEEG power as a marker for the early detection of dementia might be less conclusive for high-agers.

Sensor-based systems for early detection of dementia (SENDA): a study protocol for a prospective cohort sequential study.

BACKGROUND: Dementia and cognitive decline are serious social and economic burdens. An increase in the population of older people, as well as longer lifespans mean that numbers of dementia cases are exponentially rising. Neuropathological changes associated with dementia are thought to appear before the clinical manifestation of cognitive symptoms, i.e., memory impairments. Further, some older adults (OA) experience cognitive decline before it can be objectively diagnosed. For optimal care of these patients, it is necessary to detect cognitive decline and dementia at an early stage. In this vein, motor, sensory, and neurophysiological declines could be promising factors if found to be present before the onset of cognitive impairment. Hence, the objective of the SENDA study is to develop a multi-dimensional sensor-based instrument that allows early detection of cognitive decline or dementia in OA with the help of cognitive, sensory, motor, and neurophysiological parameters before its clinical manifestation. METHODS/DESIGN: In the cohort sequential study, participants are assigned to one of three study groups depending on their cognitive status: 1. cognitively healthy individuals (CHI), 2. subjectively cognitively impaired persons (SCI), or 3. (possible) mildly cognitively impaired persons (pMCI, MCI). All groups take part in the same cognitive (e.g., executive function tests), motor (e.g., gait analyses, balance tests), sensory (e.g., vibration perception threshold test, proprioception tests), and neurophysiological (e.g., electroencephalograms) measurements. Depending on the time at which participants are included into the study, all measurements are repeated up to four times in intervals of 8 months within 3 years to identify associations with cognitive changes over time. DISCUSSION: This study aims to detect possible motor, sensory, neurophysiological, and cognitive predictors to develop an early screening tool for dementia and its pre-stages in OA. Thus, affected persons could receive optimal health care at an earlier time point to maintain their health resources. TRIAL STATUS: The study is ongoing. The recruitment of participants will be continued until May 2020.