Human Performance
Age-related differences in fine motor control are characterized by general slowing and higher variability. Little is known about the early stages of the deterioration of fine motor control. The main research question of my dissertation was how age and expertise influence fine motor control during the middle-aged lifespan with particular attention to possible effects of task characteristics, i.e. uni- or bimanual tasks, required various target profiles, speeds, and force levels.
Three series of experiments have been conducted using uni- and bimanual tasks in different age groups (young, early middle-aged, and late middle-aged adults) and practice levels (novices and experts) collecting kinetic (force control and coordination) and neurophysiological (EEG) data.
Performance deteriorated with increasing age. Age-related differences were higher in bi- than in unimanual tasks and in tasks requiring comparably high force production per time. Reduced attention allocation with increasing age was a decisive factor - deficits occurred during innervating both hands at the same time, integrating different coordination patterns of both hands, and integrating visual feedback. Additionally, middle-aged compared to younger adults initiated corrective movements more slowly. Experts outperformed novices in all tasks. This indicates positive plasticity. Fine motor control of experts was more efficient on a behavioral as well as a neurophysiological level.
Age affects fine motor control already in middle-aged adults. The amount of remarkable age-related loss depends on task characteristics. Extensive and dexterous use of hands leads to maintenance or even improvement of fine motor control. Our results contribute to a better understanding of the underlying mechanisms of age- and expertise-related differences in fine motor control and they provide useful starting points to future research on bimanual coordination, learning, and neurophysiological correlates over the lifespan.
With age, one's tactile perception declines. But tactile expertise and short-term tactile learning can induce cortical plasticity and improve tactile perception. Thus, tactile learning might contribute to the maintenance of tactile perception. Open questions were how age and expertise influence tactile perception and learning in middle-aged adults and how the respective electrophysiological correlates are shaped by age, expertise, and learning.
We investigated tactile discrimination and event-related potentials as markers of somatosensory and cognitive processing. Participants were of different age groups [young (18-25 years), early middle-aged (35-45 years), and late middle-aged adults (55-65 years)] and expertise levels [non-experts (service employees) and experts (precision mechanics)]. Learning was induced by repetitive tactile stimulation.
Late middle-aged performed worse than young and early middle-aged adults. Somatosensory excitability increased and processing speed reduced with age. P300 topography suggested attempted compensation and reduced availability of attentional resources in late middle-aged non-experts. Experts outperformed non-experts, revealed greater somatosensory excitability, and needed less attentional resources, as compared to non-experts. This suggested that comparable electrophysiological changes induced by age and expertise have different underlying mechanisms.
Experts improved more than non-experts from the intervention, indicating meta-plasticity. Lower baseline performance was associated with higher learning. Intervention-related changes in P300 indicated that younger adults processed tactile stimuli faster, while older adults became better able to cognitively evaluate the stimuli. Experts established more specific brain activation, with a strong parietal-to-frontal gradient, pointing to more automated processing.
Results further the understanding of tactile perception in middle-aged adults and opened up new research questions.
In late adulthood, cognitive performance declines and brain structure deteriorates. However, research indicates that both may be diminished by certain lifestyle factors. Physical activity, especially cardiovascular activity, has been revealed as such a lifestyle factor, which benefits both cognitive performance and its neural correlates. This dissertation examined in four empirical studies how coordinative activity in healthy older adults is associated with changes or individual differences in cognitive functioning and brain structure and whether effects of cardiovascular and coordinative activity differ from each other.
Results indicate that motor fitness was positively related to volume of the hippocampus, basal ganglia and anterior cingulate gyrus and white matter microstructure in the medial frontal gyrus and the anterior commissure. Coordination training was shown to increase volume of the hippocampus, caudate and globus pallidus. Additionally, coordinative activity was positively associated with executive control and perceptual speed. Less evidence was found for beneficial effects of cardiovascular activity. White matter microstructure in frontal brain regions was positively related to cardiovascular fitness and cardiovascular training increased hippocampal volume. Senior dancing activity, however, did not benefit cognitive functioning and its effects on the brain were small in size and limited to frontal regions only. Thus, coordinative activity had stronger effects on brain structure than cardiovascular activity. The relationship between volumetric changes in the brain following physical activity and cognitive improvements in older adults remains largely diffuse.
Findings of the current dissertation have practical implications for the design of physical activity interventions for older adults and highlight the need for future intervention studies exploring the effects of coordinative activity on cognitive performance and brain structure and function.
