C01 - Embodied cognitive reserve in the cortico-subcortical premotor network

In the recent past, the mechanisms that enable cognitive performance and learning to be maintained
despite age-related changes of the brain have increasingly attracted the attention of neuroscience
research. Surprisingly, however, comparatively little is known about the mechanisms underlying age-related changes in mobility and balance, despite the fact that cognitive processes depend on brain-body interactions and that a functioning motor system is an important component of successful ageing. A growing body of work demonstrated the significant impact of sensorimotor signals for precise spatial orientation - an embodied cognitive mechanism that could, for example, be exploited by sensorimotor (balance) training to maintain cognitive performance in old age. The aim of the present project is to identify the brain processes that enable some people to cope better than others with the progressive degradation of the supraspinal and musculoskeletal components of the sensorimotor system with ageing, ultimately contributing to interindividual differences in both motor performance (e.g., balance performance and learning, susceptibility to falls) and visuo-spatial cognition. To explain this behavioural heterogeneity, we propose an extension of the supply-demand mismatch theory of neural plasticity to include a “neurobiological capital” component (brain reserve) - i.e., stable (non-modifiable) structural traits that are not responsive to environmental stimuli (such as training) but still predict current performance as well as future improvements in a task (learning). We are particularly interested in the relative importance of brain reserve versus experience-induced plasticity in moderating the effects of frailty and brain ageing on postural control and associated visuospatial cognition, as well as possible interactions between these two factors. To address these questions, we will conduct a randomised, controlled balance training intervention study in older people and analyse the data in four work packages from different angles. Based on previous findings, we hypothesise that structural features of secondary motor network nodes (PMC, SMA) and their associated fibre connections play an important role in the implementation of an individual's ability to cope with sensorimotor decline. More specifically, we assume that cortical surface geometry acts as neurobiological capital (brain reserve), while training-induced changes e.g. in synaptic and myelin-related processes may represent promising, behaviourally relevant plasticity. To test these neurobiologically inspired hypotheses, we will use a combination of powerful 3T and ultra-high resolution 7T structural MRI together with state-of-the-art biophysical modelling, tractography and cutting-edge multivariate statistics. In terms of balance performance, we will use video-based human movement analysis in combination with deep learning techniques to identify behavioural patterns in balance adaptation and improvement and eventually relate these patterns to visuo-spatial performance in a concurrent cognitive task. The project promises to extend our understanding of neural plasticity by integrating insights from longitudinal training studies, multivariate (reserve) analyses, and advanced neuroimaging techniques. It stands to significantly impact the field of cognitive neuroscience related to ageing, informing precision medicine/prevention strategies to optimise the cognitive capacities of the elderly.