Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

The gradually growing cohort of older citizens is one of the most important socio-economic problems in today’s society. It is crucial that older individuals continue to live independently for as long as possible. Therefore a thorough knowledge of pathologies, that may hinder the cognitive and motor functioning of older adults, is absolutely necessary. However, even in clinically healthy older individuals significant effects of age-related brain atrophy are present, that eventually may influence performance of daily-life activities. In the current project, the changes of the central nervous system that form the basis of age-related changes in motor control were studied in detail. Medical imaging techniques, such as functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging (DTI), were used to visualize brain activation and brain structure respectively.In Phase I, the parameters of age-related brain activation were established in the context of (a) ipsilateral hand-foot coordination according to an easy and a difficult movement pattern, and (b) single limb drawing movements, reflecting eye-hand coordination. The spatiotemporal characteristics of these tasks required integration of cognitive and motor brain regions, allowing unique insights into the differentiated activation patterns as a result of brain aging. The results showed that healthy older adults exhibited a significantly altered brain function. This was accompanied by an overall increased variability of movements. For both hand-foot and eye-hand coordination, old as compared to young subjects showed enhanced processing of sensory information and increased attention to action, resulting in increased brain activity in frontoparietal networks. With regard to hand-foot coordination a decreased age-related recruitment of the contralateral motor cortex, supplementary motor area and bilateral putamen was also found. We speculate that this could represent early degeneration of the “motor loop” of the basal ganglia. Although no behavioral differences were observed between execution of the hand-foot coordination with the left as opposed to the right body side, fMRI data showed that movements with the left body side were associated with more ipsilateral cortical and more contralateral cerebellar activation in both young and old subjects. With respect to eye-hand coordination, older adults, despite their generally increased brain activity, were still able to increase their brain activation additionally when a second task had to be performed simultaneously with the primary task, i.e. a dual-task condition. This may imply that the old brain still has some form of flexibility when cognitive demands increase. Furthermore it suggests that the residual brain capacity allowed older adults to perform the dual-task with minimal performance decrements when compared to single-task performance.In Phase II of the project, postural control was linked to functional and structural brain aging, which can be of high importance with respect to the prevention of falls in older adults. More specifically, postural control was tested under conditions of increased cognitive/visuospatial load. Subjects performed mental rotations of abstract figures either in a sitting or standing position. Additionally, brain activation related to these mental rotations was measured using fMRI. The data showed that on average old as compared to young individuals had more body sway when standing on a stable surface and their body sway increased when performing the mental rotations. However, older subjects with high lingual gyrus activation preserved or even optimized their visuospatial performance when postural load increased, i.e. when shifting from the seated to the standing position, whereas no such association was found in the young group. Older adults with a high degree of early visual processing may have chosen to apply an improved rotation solving strategy when standing upright. Additionally, we examined older subjects’ postural performance under conditions that required sensory reweighting by using the modified Sensory Organization Test (Neurocom International Inc.). This test systematically manipulated sensory inputs (i.e. proprioception of the ankle joint, vision, or both) while measuring a subject’s ability to maintain equilibrium. The results showed that old as compared to young subjects had significantly lower postural control when proprioception of the ankle alone, or both proprioception of the ankle and visual feedback were manipulated. These results argued for increased difficulties with reweighting sensory inputs with aging. More importantly, brain-behaviour correlations showed that a decrease in the integrity of the frontal forceps of the corpus callosum was associated with decreased postural control, when proprioceptive feedback of the ankle was manipulated. When both proprioception of the ankle and visual feedback were manipulated, the integrity of the occipital forceps was predictive of balance performance. This may imply that, apart from corticocerebellar and vestibular tracts, intracortical tracts play an equally important role in postural control.In summary, this PhD project has provided new insights into the neural substrates underlying age-related changes in motor coordination. Despite the overall increased brain function it seems that some form of neural flexibility is maintained even in old age. Nevertheless more research is needed to relate altered brain structure to functional and behavioural changes, as well as to determine changes in functional connectivity. A complete understanding of the age-related neural correlates of motor control will only be possible when multiple neuroimaging analyses are combined with neuropsychological screening, kinematic analyses and other techniques (for example genotyping). Nevertheless from our results as well as from the current literature, it seems clear that when developing intervention strategies to improve general motor function and postural control in advanced age, it is important to focus as much on the central processing, as on the musculoskeletal aspects of motor control

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)