Abstract des Autors

Physical exercise has been shown to elicit neuroplasticity and to enhance cognitive
functions in humans across the life span. However, it is still unknown which features of
physical training are mediators of exercise-related neuroplasticity. Previous studies have
focused on the effects of aerobic exercise, assuming a link between increased
cardiorespiratory fitness and exercise-induced neuroplasticity. Recent findings, however,
have suggested that whole-body exercise with less metabolic demands can elicit beneficial effects on brain structure and cognitive functions too. Here, we investigated whether balance training, placing demands particularly on vestibular self-motion perception and thus stimulate vestibular neural pathways induces gray matter changes in the brain and enhances cognitive functions in healthy adults. To this end, sighted adults were randomly assigned to either balance training or relaxation training. Pre- and posttests assessed balance performance, cardiorespiratory fitness, memory, spatial cognition, and executive functions. Moreover, TI-weighted structural Magnet Resonance Imaging (MRI) data were acquired. After 12 weeks of training, the balance group significantly improved in balance performance compared to the relaxation group. Cardiorespiratory fitness remained unchanged in both groups. The balance performance improvement was accompanied by enhanced memory and spatial cognition in the balance group (Study I ; see Appendix A).
The results suggest that an increase in cardiorespiratory fitness seems not to be a
prerequisite for beneficial effects on cognitive functions. Rather, vestibular pathways
might account for balance performance improvements as well as enhanced cognitive
functions. Structural MRI data revealed larger gray matter changes in vestibular and
visual brain areas in the balance group than in the relaxation group (Study II; see
Appendix B). These findings further support the hypothesis that a training stimulating
particularly visual-vestibular neural pathways might account for improved balance
performance and structural plasticity. Balance performance in the absence of vision is
typically poorer than with sight. Previous studies have suggested that blind individuals
can compensate the loss of vision in certain non-visual tasks by extensive practice. The
third study investigated whether balance training, which places particular demands on
vestibular and proprioceptive self-motion perception improves balance performance in
blind adults, and whether we find similar structural plasticity in cortical and subcortical
brain areas as have been reported in sighted individuals. To this end, blind adults were
randomly assigned to the same balance or relaxation training paradigm as the sighed
adults (the latter, however, trained with visual input). Assessments prior to and after
training included balance tests and the acquisition of T1-weighted MRI data. After 12
weeks of training, the blind balance group significantly improved in dynamic, static, and
functional balance performance compared to the blind relaxation group. The balance
performance improvement did not differ from that of age- and gender matched sighted
adults after balance training. MRI data revealed structural plasticity in the insular cortex
bilaterally in the blind balance group compared to the blind relaxation group. Insular gray
matter changes were related to enhanced static and functional balance perfotmance.
Moreover, changes in gray matter were observed in the parahippocampal gyrus and in
the hippocampal formation after balance training, but not after relaxation training (Study
III, see Appendix C). The findings suggest that impaired balance performance in blind
individuals can be significantly improved by a training stimulating neural pathways
which are related to vestibular and proprioceptive self-motion information. Taken
together, the present results show that balance training is capable of improving balance
performance in sighted and blind adults, accompanied by structural plasticity in brain
regions associated with self-motion perception and improved cognitive functions such as
memory and spatial abilities. Vestibular pathways might mediate the link between enhanced balance performance, structural plasticity and improved cognitive functions,
possible reflecting a general mechanism how physical exercise enhances neuroplasticity
and cognive functions.