Biology subjects

de Witte, A.

Publications and source records attributed to de Witte, A..

4 recordsLinked to original sources

bioRxiv2026

Cerebellar function remains resilient under increased task demands in healthy adults up to 80 years but it is task-specific and independent of cerebellar structure

Healthy aging is associated with progressive structural brain decline, yet the loss of functional abilities varies across individuals, which has been linked to reserve mechanisms. Within the framework of complex systems theory, reserve is thought to manifest as resilience when the system is challenged by stressors, such as increases in task difficulty. The cerebellum has been proposed as a potential source of motor reserve, but empirical evidence linking cerebellar structure, function, and resilience remains limited. We conducted a cross-sectional study including 50 young, 80 older, and 30 older-old adults to examine resilience to increasing task demands across cerebellar-specific and general outcomes. Participants completed three motor tasks (pure elbow motion, motor timing, postural stability) and two cognitive tasks (mental rotation, spatial working memory). Structural MRI was acquired to quantify cerebellar grey matter volume within functionally defined regions. Cerebellar-specific motor measures (anticipatory muscle activation and timing variability) were preserved across age groups and remained resilient under increased task demands, including in adults over 80 years of age. In contrast, general sensorimotor performance (postural sway) declined with age and showed reduced resilience. Within the cognitive domain, both cerebellar-specific and general measures showed comparable age-related declines and reduced resilience. Resilience measures were not correlated across tasks, indicating that resilience is task- and domain-specific. Furthermore, cerebellar grey matter volume did not predict resilience in motor or cognitive outcomes. These findings support the cerebellar motor reserve hypothesis, suggesting that cerebellar-dependent motor processes remain resilient despite age-related structural decline. However, resilience appears to be function-specific rather than a generalized individual trait. Overall, the results highlight dissociations between brain structure, function, and resilience, underscoring the selective contribution of the cerebellum to motor preservation in healthy aging.

neuroscience↗

bioRxiv2026

Aging is associated with uniform structural decline across cerebellar regions while preserving topological organization and showing no relation with sensorimotor function

Aging affects cerebellar structure, yet the regional specificity of this decline and its relationship to sensorimotor functions remain unclear. In this study, we quantified age-related cerebellar gray matter differences in 50 young and 80 older adults using both anatomically defined cerebellar parcellations and a functionally defined cerebellar atlas. Across both anatomical and functional parcellations, older adults showed robust reductions in gray matter volume relative to young adults. This age-related gray matter vulnerability was region-specific as age differences varied significantly across regions: both the current dataset and the additionally used Cam-CAN dataset demonstrated a larger negative effect of age in the posterior than the anterior lobe, and a smaller difference in the action domains than in the other functional domains . Structural covariance analyses revealed that correlations between cerebellar regions were determined primarily by spatial proximity and, to a lesser extent, by medial-ateral (vermis-hemisphere) organization or functional similarity. Importantly, the topological organization of the cerebellum did not differ across age groups, indicating preserved structural patterns despite widespread gray matter loss. Finally, despite substantial interindividual variability in behavioral, regional cerebellar gray matter volumes, whether anatomically or functionally defined, did not predict inter-individual variability for any of our eight cerebellum-dependent outcomes. This absence of structure-function relationship suggests that behavioral performance is maintained through compensatory mechanisms or microstructural features not captured by regional gray matter volume. Together, the results suggest heterogeneous age-related cerebellar degeneration alongside preserved topological organization and no measurable impact on cerebellar sensorimotor function, supporting the notion of a robust cerebellar reserve throughout healthy aging.

neuroscience↗

bioRxiv2025

Adults up to 80 years old maintain effective movement planning when facing complex body dynamics

Aging can significantly impact motor performance, especially in highly complex tasks such as multi-joint movements where the nervous system needs to adequately coordinate mechanical interactions between joints. This coordination is inherently challenging for the brain. Effective coordination of multiple joints relies on intact feedforward control to predict movement dynamics in the initial phase of the movement, and on feedback control to fine-tune the execution in the final phase. However, the effect of aging on these specific control mechanisms remains controversial. In our experiment we investigated a pure elbow motion task using the KINARM exoskeleton. A group of 50 young (20-35 years old), 80 old (55-70 years old) and 30 older-old (80+ years old) healthy participants were recruited. Each participant performed 30{degrees} elbow rotations while stabilizing the shoulder joint. Movements were directed toward two distinct targets in both flexion and extension directions. The task was performed under two controlled speed conditions to maximally challenge the motor system, as higher elbow velocities increase interaction torques at the shoulder, demanding greater neuromuscular effort for stabilization. The timing and magnitude of anticipatory EMG activity of the agonist shoulder muscle, necessary to counteract interaction torques, were preserved across all age groups. Moreover, increasing elbow velocity did not result in any performance differences between young and older old adults, indicating that shoulder stabilization during movement initiation remained intact with age. However, older adults exhibited reduced ability to stabilize the shoulder position until the end of the movement, leading to decreased reaching accuracy with older age. These results suggest that feedforward control, essential for movement planning, which is essential for shoulder stabilization during initiation, is preserved during healthy aging and remains resilient to increased motor demands, even in older old adults. In contrast, feedback control appears to deteriorate with age, potentially contributing to reduced movement precision in the final phase of the multi-joint movement.

neuroscience↗

bioRxiv2025

Preserved cerebellar functions despite structural degeneration in older adults

Aging is frequently perceived negatively due to its association with the decline of various brain and bodily functions. While it is evident that motor abilities deteriorate with age, it is incorrect to assume that all aspects of movement execution are equally affected. The cerebellum, a brain region that is closely involved in motor control among other functions, undergoes clear structural changes with aging. While several studies suggest that cerebellar degeneration causes age-related motor control deficits, other studies suggest that the cerebellum might act as a motor reserve and compensate for its structural degeneration, leaving cerebellar motor function intact despite cerebellar degeneration. The present study aims at thoroughly investigating the impact of age on cerebellar function across an array of tasks and domains. We investigated cerebellar motor and cognitive functions across the lifespan by examining 50 young adults (20-35 years), 80 older adults (55-70 years), and 30 older-old adults (>80 years). Participants completed a test battery comprising seven motor control tasks and one cognitive task, each designed to probe cerebellar function through different paradigms. This multi-task approach allowed for a comprehensive evaluation of performance patterns, providing a balanced perspective on cerebellar function across the different age groups. In addition, we analyzed outcomes from the same tasks that, while related to movement, were not specifically linked to cerebellar function. Structural magnetic resonance imaging was also conducted to assess whether cerebellar atrophy was present in the older and older-old groups compared to the young. Our results revealed that, despite age-related cerebellar degeneration, cerebellar functions in older adults remained intact compared to young adults, even in adults above 80 years old. In contrast, the sensorimotor measures that were not directly linked to cerebellar function exhibited a clear pattern of decline in older adults, and were further deteriorated in the older-old adults compared to the older adults. These findings indicate that cerebellar motor control functions remain largely preserved with age, providing compelling evidence that the cerebellum possesses a remarkable degree of functional resilience and redundancy. This suggests that cerebellar circuits may be uniquely equipped to preserve function despite structural degeneration.

neuroscience↗