De Sanctis, P. | Search bioRxiv

bioRxiv2021

Neural signature of everyday function in older adults at-risk of cognitive impairment

Assessment of everyday activities are central to the diagnosis of pre-dementia and dementia. Yet, little is known about the brain substrates and processes that contribute to everyday functional impairment, particularly during early stages of cognitive decline. We investigated everyday function using a complex gait task in normal older adults stratified by risk of cognitive impairment. We applied a novel EEG approach, which combines electroencephalographic with 3D-body tracking technology to measure brain-gait dynamics with millisecond precision while participants are in motion. Twenty-six participants (mean age = 74.9 years) with cognitive and everyday functional profiles within the normal range for their age and sex were ranked for risk of cognitive impairment. We used the Montreal Cognitive Assessment battery, a global index of cognition with a range from 0 to 30, to classify individuals as being at higher (22-26) and lower risk (27+). Individuals walking on a treadmill were exposed to visual perturbation designed to destabilize gait. Assuming that brain changes precede behavioral decline, we predicted that older adults increase step width to gain stability, yet the underlying neural signatures would be different for lower versus higher risk individuals. When pooling across risk groups, we found that step width increased and fronto-parietal activation shifted from transient, during swing phases, to sustained across the gait cycle during visually perturbed input. As predicted, step width increased in both groups but underlying neural signatures were different. Fronto-medial theta (3-7Hz) power of gait-related brain oscillations were increased in higher risk individuals during both perturbed and unperturbed inputs. On the other hand, left central gyri beta (13-28Hz) power was decreased in lower risk individuals, specifically during visually perturbed input. Finally, relating MoCA scores to spectral power pooled across fronto-parietal regions, we found associations between increased theta power and worse MoCA scores and between decreased beta power and better MoCA scores.Able-bodied older adults at-risk of cognitive impairment are characterized by unique neural signatures of mobility. Stronger reliance on frontomedial theta activation in at-risk individuals may reflect higher-order compensatory responses for deterioration of basic sensorimotor processes. Region and spectral-specific signatures of mobility may provide brain targets for early intervention against everyday functional decline.

neuroscience↗

bioRxiv2019

Mobile Brain/Body Imaging of cognitive-motor impairment in multiple sclerosis: deriving EEG-based neuro-markers during a dual-task walking study

Individuals with a diagnosis of multiple sclerosis (MS) often present with deficits in the cognitive as well as the motor domain. The ability to perform tasks that rely on both domains may therefore be particularly impaired. Yet, behavioral studies designed to measure costs associated with performing two tasks at the same time such as dual-task walking have yielded mixed results. Patients may mobilize additional brain resources to sustain good levels of performance. To test this hypothesis, we acquired event-related potentials (ERP) in thirteen individuals with MS and fifteen healthy control (HC) participants performing a Go/NoGo response inhibition task while sitting (i.e., single task) or walking on a treadmill (i.e., dual-task). In previous work, we showed that the nogo-N2 elicited by the cognitive task was reduced when healthy adults are also asked to walk, and that nogo-N2 reduction was accompanied by sustained dual-task performance. We predicted that some MS patients, similar to their healthy peers, may mobilize N2-indexed brain resources and thereby reduce costs. Somewhat to our surprise, the HC group performed the Go/NoGo task more accurately while walking, thus showing a dual-task benefit, whereas, in line with expectation, the MS group showed a trend towards dual-task costs. The expected nogo-N2 reduction during dual-task walking was found in the HC group, but was not present at the group level in the MS group, suggesting that this group did not modulate the nogo-N2 process in response to higher task load. Regression analysis for the pooled sample revealed a robust link between nogo-N2 reduction and better dual-task performance. We conclude that impaired nogo-N2 adaptation reflects a neurophysiological marker of cognitive-motor dysfunction in MS.

neuroscience↗