Author(s): LEHMANN, N., MATKE, M., ZIEGLER, G., TAUBERT, M., PRABHU, N., Institution: OTTO VON GUERICKE UNIVERSITY MAGDEBURG, Country: GERMANY, Abstract-ID: 2109

INTRODUCTION:
Age-related loss of dendritic spines and synapses is a hallmark of the ‘disconnected brain’ and is thought to contribute to declines in motor performance and learning [1]. Although the aging brain retains substantial capacity for experience-dependent plasticity, evidence for training-induced gray matter volume changes assessed with conventional MRI has been limited [2], possibly reflecting both suboptimal intervention design and comparably low sensitivity of volumetric measures. In motor learning, optimal progress and brain plasticity critically depends on matching task difficulty to the individual’s current skill level, thereby avoiding over- and under-challenge [3,4]. Using a well-established whole-body dynamic balancing task (DBT) combined with high-gradient diffusion MRI, we therefore compared changes in gray matter microstructure following an individually optimized motor learning intervention (OPT) versus a suboptimal, under-challenged condition (SUBOPT).
METHODS:
Sixty-one healthy older adults (60–74y; 36 ♀) were randomized to OPT or SUBOPT DBT training for five weeks. Near and far transfer were assessed using untrained DBT conditions and Wii Fit tasks. Weekly MRI measurements (up to six per participant) were conducted. Diffusion-derived markers of gray matter microstructure (mean kurtosis [MK], neurite density index [NDI], orientation dispersion index [ODI]), validated against dendritic and synaptic morphology [5–7], were projected onto the cortical ribbon and analyzed using linear mixed-effects models (LMMs).
RESULTS:
The OPT group showed greater improvements on the DBT (group × time: p = .02, d = 0.65), better near transfer, and a trend toward improved far transfer compared with SUBOPT. LMMs revealed significant group × time interactions in motor-relevant regions, including the basal ganglia (putamen, pallidum), thalamus, hippocampus, and frontal motor areas, mostly with medium effect sizes. No changes were observed in control regions, confirming the regional specificity of the training-induced effects, while effects were largely absent in the cerebellar cortex.
CONCLUSION:
Optimizing brain plasticity is critical for preserving functional independence in older adults. Our results support previous work in younger adults [7], suggesting that balance skill learning can induce structural modulation of synapses. Behavioral and microstructural changes in the OPT group exceeded those in the active control group (SUBOPT), highlighting the importance of individualized training. These findings suggest that tailored interventions may help counteract age-related brain degeneration and inform early diagnosis, treatment planning, and assessment of individual training responses.

[1] Huang et al., Front Neural Circuits, 2020
[2] Gogniat et al., Neurobiol Aging, 2021
[3] Guadagnoli & Lee, J Mot Behav, 2004
[4] Lövdén et al., Psychol Bull, 2010
[5] Reveley et al., Nat Commun, 2022
[6] Irie et al., Magn Reson Med Sci, 2018
[7] Lehmann et al., J Neurosci, 2023