Moderators of Dual Task Gait Effects in Mild Cognitive Impairment and Dementia

Spatiotemporal gait parameters may provide indication about the cognitive status of individuals. Dysfunction in specific gait features has been associated with increased risk of cognitive decline. Here we use spatiotemporal gait patterns to determine whether specific cognitive domain scores moderate the effects during dual-tasking on individuals with mild cognitive impairment (MCI) and dementia. Participants (n=46; mean age: 77.0±8.9 years) with a diagnosis of cognitive impairment (n=16), or dementia (n=30) were included. They performed validated computerized cognitive assessment battery (CAB, NeuroTrax BrainCare) to obtain cognitive domain measures of executive function (EF), attention, memory, visual-spatial processing (VSP), information processing speed (IPS), and a global cognitive score (GCS) measure. Using the Zeno Walkway Gait Analysis System (Protokinetics), measures of velocity, stride width (SW), stride time (ST), stride length, cadence, double support (DS), and gait variability were obtained for both single-task and DT gait. Data analysis was conducted using SPSS 26 and PROCESS 3.5. As expected, the dementia group had lower cognitive domain scores and slower walking speed than MCI group. Results also indicated that visual-spatial processing skills was the only cognitive domain that did have a moderation effect on gait velocity (F=4.2, p<0.05, R-square change 10%). Our results indicate that differences between walking speed in MCI and dementia groups are moderated by visual spatial skills. Improvement in visual spatial skills could improve the dual task effects of individual gait measures.

Alpha Oscillatory Activity Associated with Impaired Visual Search in Cerebral Visual Impairment

Cerebral (cortical) visual impairment (CVI) is associated with perinatal damage to retrochiasmatic pathways and cerebral structures. Individuals with CVI often present with impairments in visual spatial processing and attention. However, the neural correlates associated with these higher order perceptual deficits remain unknown. In this study, we investigated visual search performance using a novel virtual reality based task combined with electroencephalography (EEG) and time frequency decomposition of recorded oscillatory activity. We found that CVI participants showed impaired visual search performance (indexed by both decreased success rates and increased reaction times) compared to age matched controls. Furthermore, analysis of captured EEG activity revealed that posterior alpha desynchronization (typically associated with coordinating neural activity in perceptual and cognitive tasks) was greatly impaired in CVI compared to control participants. Finally, exploratory analysis suggested a potential association between amplitude of oscillations in the alpha range and morphometric anatomical measures. Specifically, less alpha desynchronization following stimulus onset was correlated with decreased volume of specific thalamic nuclei. These results suggest that in the setting of early neurological damage to retrochiasmatic visual pathways, alpha desynchronization remains greatly impaired and may be related to deficits in visual spatial processing and attention commonly observed in this population.

Altered neural dynamics in occipital cortices serving visual-spatial processing in heavy alcohol users

Background: Visual-spatial processing deficits have been previously linked to heavy alcohol use, but the underlying neurological mechanisms are poorly understood. Neuroimaging studies have shown alcohol-related aberrations in occipital cortices that appear to be associated with these neuropsychological deficits in visual-spatial processing, however the neural dynamics underlying this altered processing remains unknown. Methods: Twenty-three adults with high scores on the Alcohol Use Disorders Identification Test – Consumption (male: ⩾5, female: ⩾4) were compared to 30 demographically-matched controls with low Alcohol Use Disorders Identification Test – Consumption scores (⩽2). All participants completed a visual-spatial processing task while undergoing high-density magnetoencephalography. Time-frequency windows of interest were determined using a data-driven method, and spectrally-specific neural activity was imaged using a beamforming approach. Permutation testing of peak voxel time series was then used to statistically compare across groups. Results: Participants with heavy alcohol use responded slower on the task and their performance was more variable. The magnetoencephalography data indicated strong theta (4–8 Hz), alpha (10–16 Hz), and gamma (62–72 Hz) responses in posterior brain regions across both groups. Following voxel time-series extraction, significant group differences were found in the left and right visual association cortices from about 375–550 ms post-stimulus, such that adults with heavy alcohol use had blunted alpha responses compared to controls. Conclusion: Individuals with heavy alcohol use exhibited aberrant occipital alpha activity during visual-spatial processing. These data are the first to show spectrally-specific differences during visual-spatial processing related to heavy alcohol use, and highlight alcohol’s effect on systems-level neural activity.