Abstract
Falls are the second most frequent cause of injury in the elderly. Physiological processes associated with aging affect the elderly’s ability to respond to unexpected balance perturbations, leading to increased fall risk. Every year, approximately 30% of adults, 65 years and older, experiences at least one fall. Investigating the neurophysiological mechanisms underlying the control of static and dynamic balance in the elderly is an emerging research area. The study aimed to identify cortical and muscular correlates during static and dynamic balance tests in a cohort of young and old healthy adults. We recorded cortical and muscular activity in nine elderly and eight younger healthy participants during an upright stance task in static and dynamic (core board) conditions. To simulate real-life dual-task postural control conditions, the second set of experiments incorporated an oddball visual task. We observed higher electroencephalographic (EEG) delta rhythm over the anterior cortex in the elderly and more diffused fast rhythms (i.e., alpha, beta, gamma) in younger participants during the static balance tests. When adding a visual oddball, the elderly displayed an increase in theta activation over the sensorimotor and occipital cortices. During the dynamic balance tests, the elderly showed the recruitment of sensorimotor areas and increased muscle activity level, suggesting a preferential motor strategy for postural control. This strategy was even more prominent during the oddball task. Younger participants showed reduced cortical and muscular activity compared to the elderly, with the noteworthy difference of a preferential activation of occipital areas that increased during the oddball task. These results support the hypothesis that different strategies are used by the elderly compared to younger adults during postural tasks, particularly when postural and cognitive tasks are combined. The knowledge gained in this study could inform the development of age-specific rehabilitative and assistive interventions.
Highlights
In postural s way[2,5]
We administered the Trail Making Test (TMT) A and B as a screening tool to detect visual-attention and movement speed impairments, common with aging. These deficits were considered as exclusion criteria, i.e., participants performing under the threshold of normality, based on normative values computed by taking into account the subject’s age and education level[34] were excluded
Since performance on TMT-A and TMT-B is affected by age and e ducation[35], we computed the cut-off for each participant considering these two c ovariates[36] (3rd and 5th columns of Table 1)
Summary
In postural s way[2,5]. Other studies exploring the relationship among attention, posture, and gait in younger and older adults proved that postural control is more cognitively demanding in the elderly than in younger adults. The existence of neural markers of postural instability that may trigger balance compensatory adjustments was supported by the observation that a burst of gamma activity preceded the initiation of compensatory backward posture adjustments[20] Despite their potential relevance in the above-described context, there is a lack of studies investigating the EEG and electromyographic (EMG) data in the elderly during a balance task[6]. Clusters of EEG sources obtained with Independent Component Analysis (ICA) in healthy young subjects walking heel-to-toe on a treadmill-mounted balance beam and walking on the treadmill belt at the same speed identified activations in or near the anterior cingulate, anterior parietal, superior dorsolateral-prefrontal, and medial sensorimotor cortex These areas exhibited significantly larger mean spectral power in the theta band (4–7 Hz) during walking on the balance beam compared with treadmill walking. Increased activation of antagonistic muscles appears to be associated with healthy aging in walking tasks[32], and with balance impairments in balance r ecovery[33]
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