Classification of Mild Cognitive Impairment and Alzheimer's Disease Using Manual Motor Measures.

INTRODUCTION: Manual motor problems have been reported in mild cognitive impairment (MCI) and Alzheimer's disease (AD), but the specific aspects that are affected, their neuropathology, and potential value for classification modeling is unknown. The current study examined if multiple measures of motor strength, dexterity, and speed are affected in MCI and AD, related to AD biomarkers, and are able to classify MCI or AD. METHODS: Fifty-three cognitively normal (CN), 33 amnestic MCI, and 28 AD subjects completed five manual motor measures: grip force, Trail Making Test A, spiral tracing, finger tapping, and a simulated feeding task. Analyses included: 1) group differences in manual performance; 2) associations between manual function and AD biomarkers (PET amyloid ß, hippocampal volume, and APOE ε4 alleles); and 3) group classification accuracy of manual motor function using machine learning. RESULTS: amnestic MCI and AD subjects exhibited slower psychomotor speed and AD subjects had weaker dominant hand grip strength than CN subjects. Performance on these measures was related to amyloid ß deposition (both) and hippocampal volume (psychomotor speed only). Support vector classification well-discriminated control and AD subjects (area under the curve of 0.73 and 0.77 respectively), but poorly discriminated MCI from controls or AD. CONCLUSION: Grip strength and spiral tracing appear preserved, while psychomotor speed is affected in amnestic MCI and AD. The association of motor performance with amyloid ß deposition and atrophy could indicate that this is due to amyloid deposition in- and atrophy of motor brain regions, which generally occurs later in the disease process. The promising discriminatory abilities of manual motor measures for AD emphasize their value alongside other cognitive and motor assessment outcomes in classification and prediction models, as well as potential enrichment of outcome variables in AD clinical trials.

Developmental and age differences in visuomotor adaptation across the lifespan.

In the present cross-sectional study, we examined age and sex differences in sensorimotor adaptation. We tested 253 individuals at a local science museum (NEMO Science Museum, Amsterdam). Participants spanned a wide age range (8-70 years old; 54% male), allowing us to examine effects of both development and healthy aging within a single study. Participants performed a visuomotor adaptation task in which they had to adapt manual joystick movements to rotated visual feedback. We assessed the rate of adaptation following the introduction of the visual perturbation (both for early and later stages of adaptation), and the rate of de-adaptation following its removal. Results showed reliable adaptation patterns which did not differ by sex. We observed a quadratic relationship between age and both early adaptation and de-adaptation rates, with younger and older adults exhibiting the fasted adaptation rates. Our findings suggest that both younger and older age are associated with poorer strategic, cognitive processes involved in adaptation. We propose that developmental and age differences in cognitive functions and brain properties may underlie these effects on sensorimotor functioning.

Longitudinal surface-based spatial Bayesian GLM reveals complex trajectories of motor neurodegeneration in ALS.

Longitudinal fMRI studies hold great promise for the study of neurodegenerative diseases, development and aging, but realizing their full potential depends on extracting accurate fMRI-based measures of brain function and organization in individual subjects over time. This is especially true for studies of rare, heterogeneous and/or rapidly progressing neurodegenerative diseases. These often involve small samples with heterogeneous functional features, making traditional group-difference analyses of limited utility. One such disease is amyotrophic lateral sclerosis (ALS), a severe disease resulting in extreme loss of motor function and eventual death. Here, we use an advanced individualized task fMRI analysis approach to analyze a rich longitudinal dataset containing 190 hand clench fMRI scans from 16 ALS patients (78 scans) and 22 age-matched healthy controls (112 scans). Specifically, we adopt our cortical surface-based spatial Bayesian general linear model (GLM), which has high power and precision to detect activations in individual subjects, and propose a novel longitudinal extension to leverage information shared across visits. We perform all analyses in native surface space to preserve individual anatomical and functional features. Using mixed-effects models to subsequently study the relationship between size of activation and ALS disease progression, we observe for the first time an inverted U-shaped trajectory of motor activations: at relatively mild motor disability we observe enlarging activations, while at higher levels of motor disability we observe severely diminished activation, reflecting progression toward complete loss of motor function. We further observe distinct trajectories depending on clinical progression rate, with faster progressors exhibiting more extreme changes at an earlier stage of disability. These differential trajectories suggest that initial hyper-activation is likely attributable to loss of inhibitory neurons, rather than functional compensation as earlier assumed. These findings substantially advance scientific understanding of the ALS disease process. This study also provides the first real-world example of how surface-based spatial Bayesian analysis of task fMRI can further scientific understanding of neurodegenerative disease and other phenomena. The surface-based spatial Bayesian GLM is implemented in the BayesfMRI R package.

Neural correlates of risky decision making in Parkinson's disease patients with impulse control disorders.

Some patients with Parkinson's disease (PD) experience impulse control disorders (ICDs), characterized by deficient voluntary control over impulses, drives, or temptations regarding excessive hedonic behavior. The present study aimed to better understand the neural basis of impulsive, risky decision making in PD patients with ICDs by disentangling potential dysfunctions in decision and outcome mechanisms. We collected fMRI data from 20 patients with ICDs and 28 without ICDs performing an information gathering task. Patients viewed sequences of bead colors drawn from hidden urns and were instructed to infer the majority bead color in each urn. With each new bead, they could choose to either seek more evidence by drawing another bead (draw choice) or make an urn-inference (urn choice followed by feedback). We manipulated risk via the probability of bead color splits (80/20 vs. 60/40) and potential loss following an incorrect inference ($10 vs. $0). Patients also completed the Barratt Impulsiveness Scale (BIS) to assess impulsivity. Patients with ICDs showed greater urn choice-specific activation in the right middle frontal gyrus, overlapping the dorsal premotor cortex. Across all patients, fewer draw choices (i.e., more impulsivity) were associated with greater activation during both decision making and outcome processing in a variety of frontal and parietal areas, cerebellum, and bilateral striatum. Our findings demonstrate that ICDs in PD are associated with differences in neural processing of risk-related information and outcomes, implicating both reward and sensorimotor dopaminergic pathways.

Long-term effects of adjuvant treatment for breast cancer on carotid plaques and brain perfusion.

PURPOSE: Breast cancer treatment has been associated with vascular pathology. It is unclear if such treatment is also associated with long-term cerebrovascular changes. We studied the association between radiotherapy and chemotherapy with carotid pathology and brain perfusion in breast cancer survivors. METHODS: We included 173 breast cancer survivors exposed to radiotherapy and chemotherapy, assessed ± 21.2 years after cancer diagnosis, and 346 age-matched cancer-free women (1:2) selected from the population-based Rotterdam Study. Outcome measures were carotid plaque score, intima-media thickness (IMT), total cerebral blood flow (tCBF), and brain perfusion. Additionally, we investigated the association between inclusion of the carotid artery in the radiation field (no/small/large part), tumor location, and these outcome measures within cancer survivors. RESULTS: Cancer survivors had lower tCBF (- 19.6 ml/min, 95%CI - 37.3;- 1.9) and brain perfusion (- 2.5 ml/min per 100 ml, 95%CI - 4.3;- 0.7) than cancer-free women. No statistically significant group differences were observed regarding plaque score or IMT. Among cancer survivors, a large versus a small part of the carotid artery in the radiation field was associated with a higher IMT (0.05, 95%CI0.01;0.09). Also, survivors with a right-sided tumor had lower left carotid plaque score (- 0.31, 95%CI - 0.60;- 0.02) and higher brain perfusion (3.5 ml/min per 100 ml, 95%CI 0.7;6.2) than those with a left-sided tumor. CONCLUSIONS: On average two decades post-diagnosis, breast cancer survivors had lower tCBF and brain perfusion than cancer-free women. Also, survivors with a larger area of the carotid artery within the radiation field had a larger IMT. Future studies should confirm if these cerebrovascular changes underlie the frequently observed cognitive problems in cancer survivors.

Inflammation markers and cognitive performance in breast cancer survivors 20 years after completion of chemotherapy: a cohort study.

BACKGROUND: Inflammation is an important candidate mechanism underlying cancer and cancer treatment-related cognitive impairment. We investigated levels of blood cell-based inflammatory markers in breast cancer survivors on average 20 years after chemotherapy and explored the relation between these markers and global cognitive performance. METHODS: One hundred sixty-six breast cancer survivors who received post-surgical radiotherapy and six cycles of adjuvant cyclophosphamide, methotrexate, and fluorouracil (CMF) chemotherapy on average 20 years before enrollment were compared with 1344 cancer-free women from a population-based sample (50-80 years old). Breast cancer survivors were excluded if they used adjuvant hormonal therapy or if they developed relapse, metastasis, or second primary malignancies. Systemic inflammation status was assessed by the granulocyte-to-lymphocyte ratio (GLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII). Cognitive performance was assessed using an extensive neuropsychological test battery from which the general cognitive factor was derived to evaluate global cognitive performance. We examined the association between cancer, the general cognitive factor, and inflammatory markers using linear regression models. RESULTS: Breast cancer survivors had a lower general cognitive factor than non-exposed participants from the comparator group (mean difference = -0.21; 95% confidence interval (CI) -0.35 to -0.06). Inflammatory markers were higher in cancer survivors compared with non-exposed participants (mean difference for log(GLR) = 0.31; 95% CI 0.24 to 0.37, log(PLR) = 0.14; 95% CI 0.09 to 0.19, log(SII) = 0.31; 95% CI 0.24 to 0.39). The association between higher levels of inflammatory markers and lower general cognitive factor was statistically significant in cancer survivors but not among non-exposed participants. We found a group-by-inflammatory marker interaction; cancer survivors showed additional lower general cognitive factor per standard deviation increase in inflammatory markers (P for interaction for GLR = 0.038, PLR = 0.003, and SII = 0.033). CONCLUSIONS: This is the first study to show that (1) cancer survivors have increased levels of inflammation on average 20 years after treatment and (2) these inflammatory levels are associated with lower cognitive performance. Although this association needs verification by a prospective study to determine causality, our findings can stimulate research on the role of inflammation in long-term cognitive problems and possibilities to diminish such problems.

Change of cortical foot activation following 70 days of head-down bed rest.

Head-down tilt bed rest (HDBR) has been used as a spaceflight analog to study some of the effects of microgravity on human physiology, cognition, and sensorimotor functions. Previous studies have reported declines in balance control and functional mobility after spaceflight and HDBR. In this study we investigated how the brain activation for foot movement changed with HDBR. Eighteen healthy men participated in the current HDBR study. They were in a 6° head-down tilt position continuously for 70 days. Functional MRI scans were acquired to estimate brain activation for foot movement before, during, and after HDBR. Another 11 healthy men who did not undergo HDBR participated as control subjects and were scanned at four time points. In the HDBR subjects, the cerebellum, fusiform gyrus, hippocampus, and middle occipital gyrus exhibited HDBR-related increases in activation for foot tapping, whereas no HDBR-associated activation decreases were found. For the control subjects, activation for foot tapping decreased across sessions in a couple of cerebellar regions, whereas no activation increase with session was found. Furthermore, we observed that less HDBR-related decline in functional mobility and balance control was associated with greater pre-to-post HDBR increases in brain activation for foot movement in several cerebral and cerebellar regions. Our results suggest that more neural control is needed for foot movement as a result of HDBR. NEW & NOTEWORTHY Long-duration head-down bed rest serves as a spaceflight analog research environment. We show that brain activity in the cerebellum and visual areas during foot movement increases from pre- to post-bed rest and then shows subsequent recovery. Greater increases were seen for individuals who exhibited less decline in functional mobility and balance control, suggestive of adaptive changes in neural control with long-duration bed rest.

Vestibular brain changes within 70 days of head down bed rest.

Head-down-tilt bed rest (HDBR) is frequently utilized as a spaceflight analog research environment to study the effects of axial body unloading and fluid shifts that are associated with spaceflight in the absence of gravitational modifications. HDBR has been shown to result in balance changes, presumably due to sensory reweighting and adaptation processes. Here, we examined whether HDBR results in changes in the neural correlates of vestibular processing. Thirteen men participated in a 70-day HDBR intervention; we measured balance, functional mobility, and functional brain activity in response to vestibular stimulation at 7 time points before, during, and after HDBR. Vestibular stimulation was administered by means of skull taps, resulting in activation of the vestibular cortex and deactivation of the cerebellar, motor, and somatosensory cortices. Activation in the bilateral insular cortex, part of the vestibular network, gradually increased across the course of HDBR, suggesting an upregulation of vestibular inputs in response to the reduced somatosensory inputs experienced during bed rest. Furthermore, greater increase of activation in multiple frontal, parietal, and occipital regions in response to vestibular stimulation during HDBR was associated with greater decrements in balance and mobility from before to after HDBR, suggesting reduced neural efficiency. These findings shed light on neuroplastic changes occurring with conditions of altered sensory inputs, and reveal the potential for central vestibular-somatosensory convergence and reweighting with bed rest.

Neural predictors of sensorimotor adaptation rate and savings.

In this study, we investigate whether individual variability in the rate of visuomotor adaptation and multiday savings is associated with differences in regional gray matter volume and resting-state functional connectivity. Thirty-four participants performed a manual adaptation task during two separate test sessions, on average 9 days apart. Functional connectivity strength between sensorimotor, dorsal cingulate, and temporoparietal regions of the brain was found to predict the rate of learning during the early phase of the adaptation task. In contrast, default mode network connectivity strength was found to predict both the rate of learning during the late adaptation phase and savings. As for structural predictors, greater gray matter volume in temporoparietal and occipital regions predicted faster early learning, whereas greater gray matter volume in superior posterior regions of the cerebellum predicted faster late learning. These findings suggest that the offline neural predictors of early adaptation may facilitate the cognitive aspects of sensorimotor adaptation, supported by the involvement of temporoparietal and cingulate networks. The offline neural predictors of late adaptation and savings, including the default mode network and the cerebellum, likely support the storage and modification of newly acquired sensorimotor representations.

Effects of a spaceflight analog environment on brain connectivity and behavior.

Sensorimotor functioning is adaptively altered following long-duration spaceflight. The question of whether microgravity affects other central nervous system functions such as brain network organization and its relationship with behavior is largely unknown, but of importance to the health and performance of astronauts both during and post-flight. In the present study, we investigate the effects of prolonged exposure to an established spaceflight analog on resting state brain functional connectivity and its association with behavioral changes in 17 male participants. These bed rest participants remained in bed with their heads tilted down six degrees below their feet for 70 consecutive days. Resting state functional magnetic resonance imaging (rs-fMRI) and behavioral data were obtained at seven time points averaging around: 12 and 8days prior to bed rest; 7, 50, and 70days during bed rest; and 8 and 12days after bed rest. To assess potential confounding effects due to scanning interval or task practice, we also acquired rs-fMRI and behavioral measurements from 14 control participants at four time points. 70days of head-down tilt (HDT) bed rest resulted in significant changes in the functional connectivity of motor, somatosensory, and vestibular areas of the brain. Moreover, several of these network alterations were significantly associated with changes in sensorimotor and spatial working memory performance, which suggests that neuroplasticity mechanisms may facilitate adaptation to the microgravity analog environment. The findings from this study provide novel insights into the underlying neural mechanisms and operational risks of spaceflight analog-related changes in sensorimotor performance.

Structural and functional connectivity in healthy aging: Associations for cognition and motor behavior.

Age-related behavioral declines may be the result of deterioration of white matter tracts, affecting brain structural (SC) and functional connectivity (FC) during resting state. To date, it is not clear if the combination of SC and FC data could better predict cognitive/motor performance than each measure separately. We probed these relationships in the cingulum bundle, a major white matter pathway of the default mode network. We aimed to attain deeper knowledge about: (a) the relationship between age and the cingulum's SC and FC strength, (b) the association between SC and FC, and particularly (c) how the cingulum's SC and FC are related to cognitive/motor performance separately and combined. We examined these associations in a healthy and well-educated sample of 165 older participants (aged 64-85). SC and FC were acquired using probabilistic tractography to derive measures to capture white matter integrity within the cingulum bundle (fractional anisotropy, mean, axial and radial diffusivity) and a seed-based resting-state functional MRI correlation approach, respectively. Participants performed cognitive tests measuring processing speed, memory and executive functions, and motor tests measuring motor speed and grip force. Our data revealed that only SC but not resting state FC was significantly associated with age. Further, the cingulum's SC and FC showed no relation. Different relationships between cognitive/motor performance and SC/FC separately were found, but no additive effect of the combined analysis of cingulum's SC and FC for predicting cognitive/motor performance was apparent.

Associations between age, motor function, and resting state sensorimotor network connectivity in healthy older adults.

Aging is associated with impaired motor performance across a range of tasks. Both primary neural representations of movement and potential compensatory cognitive mechanisms appear to be disrupted in older age. Here we determined how age is associated with resting state sensorimotor functional connectivity, and whether connectivity strength is associated with motor performance. We investigated the association between age and resting state functional connectivity of several sensorimotor networks in 191 healthy older, right-handed individuals. Regions of interest were defined in the left motor cortex, left putamen, and right cerebellar lobules V and VIII. Analyses were adjusted for head motion, gray matter volume, diastolic blood pressure, and smoker status; we then evaluated whether connectivity is associated with participants' manual motor performance. We found both increased and decreased connectivity within portions of the motor cortical and cerebellar networks after adjusting for covariates. We observed that connectivity increased with age for the motor cortex and cerebellar lobule VIII with the putamen, providing evidence of greater interactivity across networks with age. Higher tapping frequency and greater grip force were associated with stronger connectivity between the motor cortex during resting state, putamen, cerebellar lobule VIII and the insular cortex, suggesting that greater network interactivity may protect against age declines in performance.

Cerebellar gray and white matter volume and their relation with age and manual motor performance in healthy older adults.

OBJECTIVES: Functional neuroimaging and voxel-based morphometry studies have confirmed the important role of the cerebellum in motor behavior. However, little is known about the relationship between cerebellar gray (GMv) and white matter (WMv) volume and manual motor performance in aging individuals. This study aims to quantify the relationship between cerebellar tissue volume and manual motor performance. EXPERIMENTAL DESIGN: To gain more insight into cerebellar function and how it relates to the role of the primary motor cortex (M1), we related cerebellar GMv, WMv, and M1v to manual motor performance in 217 healthy older individuals. Left and right cerebellar GMv and WMv, and M1v were obtained using FreeSurfer. The following motor measures were obtained: grip force, tapping speed, bimanual visuomotor coordination, and manual dexterity. PRINCIPAL OBSERVATIONS: Significant positive relationships were observed between cerebellar GMv and WMv and grip strength, right cerebellar WMv and right-hand tapping speed, right cerebellar WMv and dexterity, M1v and grip strength, and right M1v and left-hand dexterity, though effect sizes were small. CONCLUSIONS: Our results show that cerebellar GMv and WMv are differently associated with manual motor performance. These associations partly overlap with the brain-behavior associations between M1 and manual motor performance. Not all observed associations were lateralized (i.e., ipsilateral cerebellar and contralateral M1v associations with motor performance), which could point to age-related neural dedifferentiation. The current study provides new insights in the role of the cerebellum in manual motor performance. In consideration of the small effect sizes replication studies are needed to validate these results.

Late effects of adjuvant chemotherapy for breast cancer on fine motor function.

BACKGROUND: Adjuvant chemotherapy for breast cancer has been associated with deterioration of fine motor skill. Which aspects of motor performance are underlying this problem is unclear but important because manual motor deterioration could affect quality of life. The current study aims to investigate late effects of adjuvant chemotherapy for breast cancer on fine motor function, using both speed and accuracy measures. METHOD: We compared fine motor function of 174 women who had received adjuvant Cyclophosphamide Methotrexate 5-Fluorouracil chemotherapy for breast cancer on average 20 years ago with that of a population sample of 195 women without a history of cancer. Fine motor function was measured with the Purdue Pegboard Test and the Archimedes spiral test. RESULTS: The group of chemotherapy-exposed breast cancer survivors was slower in drawing an Archimedes spiral than the reference group. Furthermore, in the chemotherapy-exposed subjects, we found that older age is related to more crossings of the spiral template, more return movements, and more deviations from the template. Such relationships were not observed within the reference group. No significant between-group differences were found for any of the Purdue Pegboard measures. CONCLUSIONS: Compared with a population-based reference group, Cyclophosphamide Methotrexate 5-Fluorouracil chemotherapy-exposed breast cancer survivors demonstrated motor slowing while drawing an Archimedes spiral, on average 20 years after completion of primary treatment. Furthermore, the Archimedes spiral test is a more sensitive measure than the Purdue Pegboard Test to assess fine manual motor performance in long-term breast cancer survivors following chemotherapy.

Global and focal white matter integrity in breast cancer survivors 20 years after adjuvant chemotherapy.

OBJECTIVES: To date, only four small studies have investigated the effects of adjuvant chemotherapy for breast cancer on the microstructure of cerebral white matter with magnetic resonance imaging (MRI). These studies, which were conducted shortly up to 10 years post-treatment, showed that chemotherapy is associated with focal loss of microstructural white matter integrity. We investigated the long-term effect of chemotherapy on white matter microstructural integrity by comparing the brains of chemotherapy-exposed breast cancer survivors to those of a population-based sample of women without a history of cancer. EXPERIMENTAL DESIGN: Diffusion tensor imaging (DTI) MRI (1.5 T) was performed in 187 CMF (cyclophosphamide, methotrexate, and 5-flourouracil) chemotherapy-exposed breast cancer survivors, mean age 64.2 (sd = 6.5) years, who had been diagnosed with cancer on average 21.2 (sd = 4.4) years before, and 374 age-matched cancer-free reference subjects from a population-based cohort study. Outcome measures were whole-brain microstructural integrity as measured by fractional anisotropy and mean/axial/radial diffusivity and focal white matter integrity, which was analyzed with tract-based spatial statistics. All analyses were adjusted for age, cardiovascular risk factors, education, and symptoms of depression. PRINCIPAL OBSERVATIONS: No significant group differences were observed in white matter integrity. However, within the breast cancer survivors, time since treatment was inversely associated with lower global and focal white matter integrity. CONCLUSIONS: This cross-sectional study suggests that among chemotherapy-exposed breast cancer survivors white matter microstructural integrity deteriorates with accumulating time since treatment. This warrants further investigation.

Short-Term Practice Effects on Cognitive Tests Across the Late Life Cognitive Spectrum and How They Compare to Biomarkers of Alzheimer's Disease.

Background: Practice effects on cognitive testing in mild cognitive impairment (MCI) and Alzheimer's disease (AD) remain understudied, especially with how they compare to biomarkers of AD. Objective: The current study sought to add to this growing literature. Methods: Cognitively intact older adults (n = 68), those with amnestic MCI (n = 52), and those with mild AD (n = 45) completed a brief battery of cognitive tests at baseline and again after one week, and they also completed a baseline amyloid PET scan, a baseline MRI, and a baseline blood draw to obtain APOE ɛ4 status. Results: The intact participants showed significantly larger baseline cognitive scores and practice effects than the other two groups on overall composite measures. Those with MCI showed significantly larger baseline scores and practice effects than AD participants on the composite. For amyloid deposition, the intact participants had significantly less tracer uptake, whereas MCI and AD participants were comparable. For total hippocampal volumes, all three groups were significantly different in the expected direction (intact > MCI > AD). For APOE ɛ4, the intact had significantly fewer copies of ɛ4 than MCI and AD. The effect sizes of the baseline cognitive scores and practice effects were comparable, and they were significantly larger than effect sizes of biomarkers in 7 of the 9 comparisons. Conclusion: Baseline cognition and short-term practice effects appear to be sensitive markers in late life cognitive disorders, as they separated groups better than commonly-used biomarkers in AD. Further development of baseline cognition and short-term practice effects as tools for clinical diagnosis, prognostic indication, and enrichment of clinical trials seems warranted.

Study protocol to examine the effects of spaceflight and a spaceflight analog on neurocognitive performance: extent, longevity, and neural bases.

BACKGROUND: Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether spaceflight also affects other central nervous system functions such as cognition is yet largely unknown, but of importance in consideration of the health and performance of crewmembers both in- and post-flight. We are therefore conducting a controlled prospective longitudinal study to investigate the effects of spaceflight on the extent, longevity and neural bases of sensorimotor and cognitive performance changes. Here we present the protocol of our study. METHODS/DESIGN: This study includes three groups (astronauts, bed rest subjects, ground-based control subjects) for which each the design is single group with repeated measures. The effects of spaceflight on the brain will be investigated in astronauts who will be assessed at two time points pre-, at three time points during-, and at four time points following a spaceflight mission of six months. To parse out the effect of microgravity from the overall effects of spaceflight, we investigate the effects of seventy days head-down tilted bed rest. Bed rest subjects will be assessed at two time points before-, two time points during-, and three time points post-bed rest. A third group of ground based controls will be measured at four time points to assess reliability of our measures over time. For all participants and at all time points, except in flight, measures of neurocognitive performance, fine motor control, gait, balance, structural MRI (T1, DTI), task fMRI, and functional connectivity MRI will be obtained. In flight, astronauts will complete some of the tasks that they complete pre- and post flight, including tasks measuring spatial working memory, sensorimotor adaptation, and fine motor performance. Potential changes over time and associations between cognition, motor-behavior, and brain structure and function will be analyzed. DISCUSSION: This study explores how spaceflight induced brain changes impact functional performance. This understanding could aid in the design of targeted countermeasures to mitigate the negative effects of long-duration spaceflight.

Repeatable battery for the assessment of neuropsychological status and its relationship to biomarkers of Alzheimer's disease.

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) has been associated with commonly used biomarkers of Alzheimer's disease (AD). However, prior studies have typically utilized small and poorly characterized samples, and they have not analyzed the subtests of the RBANS. The current study sought to expand on prior work by examining the relationship between the Indexes and subtest scores of the RBANS and three AD biomarkers: amyloid deposition via positron emission tomography, hippocampal volume via magnetic resonance imaging, and APOE ε4 status.One-hundred twenty-one older adults across the AD continuum (intact, amnestic Mild Cognitive Impairment, mild AD), who were mostly Caucasian and well-educated, underwent assessment with the RBANS and collection of the three biomarkers.Greater amyloid deposition was significantly related to lower scores on all five Indexes and the Total Scale score of the RBANS, as well as 11 of 12 subtests. For bilateral hippocampal volume, significant correlations were observed for 4 of the 5 Indexes, Total Scale score, and 9 of 12 subtests, with smaller hippocampi being related to lower RBANS scores. Participants with at least one APOE ε4 allele had significantly lower scores on 3 of the 5 Indexes, Total Scale score, and 8 of the 12 subtests.In this sample of participants across the dementia spectrum, most RBANS Indexes and subtests showed relationships with the amyloid deposition, hippocampal volumes, and APOE status, with poorer performance on the RBANS being associated with biomarker positivity. Although memory scores on the RBANS have traditionally been linked to biomarkers in AD, other Index and subtest scores also hold promise as indicators of AD. Replication in a more diverse sample is needed.

Volumetric regional MRI and neuropsychological predictors of motor task variability in cognitively unimpaired, Mild Cognitive Impairment, and probable Alzheimer's disease older adults.

INTRODUCTION: The mechanisms linking motor function to Alzheimer's disease (AD) progression have not been well studied, despite evidence of AD pathology within motor brain regions. Thus, there is a need for new motor measure that is sensitive and specific to AD. METHODS: In a sample of 121 older adults (54 cognitive unimpaired [CU], 35 amnestic Mild Cognitive Impairment [aMCI], and 32 probable mild AD), intrasubject standard deviation (ISD) across six trials of a novel upper-extremity motor task was predicted with volumetric regional gray matter and neuropsychological scores using classification and regression tree (CART) analyses. RESULTS: Both gray matter and neuropsychological CART models indicated that motor task ISD (our measure of motor learning) was related to cortical regions and cognitive test scores associated with memory, executive function, and visuospatial skills. CART models also accurately distinguished motor task ISD of MCI and probable mild AD from CU. DISCUSSION: Variability in motor task performance across practice trials may be valuable for understanding preclinical and early-stage AD.