Functional magnetic resonance imaging reveals age-related alterations to motor networks in weighted elbow flexion-extension movement

Objective: we investigated whether motor system activity in normal aging shows age-related alteration during a non-isomeric elbow flexion-extension movement task using weights. Methods: Twenty-six healthy, right-handed elderly and 20 healthy, right-handed young subjects without any psychiatric, neurological, or medical disease participated in this study. All subjects underwent two consecutive scanning sessions: one without weights, and one with weights. During the weights session, each subject held a small non-metallic bar (weighing approximately 1 kg) with their dominant hand and performed elbow flexion and extension movements. Functional magnetic resonance imaging BOLD contrast was obtained for each subject using a 3.0 T MRI scanner. Image processing and statistical analyses were carried out using SPM2. In fMRI data group analysis, contrast images from the analysis of individual subjects were analysed by one-sample t-tests, thereby generating a random-effects model, allowing inference to the general population. The SPM{t}s were thresholded at P < 0.01, false discovery rate (FDR) corrected for multiple comparisons across the whole brain. Finally, the resulting activation maps were created and displayed by projection onto the anatomically standardized mean T1 image of all subjects to identify the anatomical correlates of the activity. Results: It was revealed that the main change in the aging brain was significant activation of the ipsilateral basal ganglia-thalamo-cortical motor loop in older subjects, suggesting the recruitment of additional brain areas during the execution of a weighted elbow motor task as a compensation process for age-related neurobiological change. Conclusion: The current study is the first to demonstrate significant differences in brain activation between old and young subjects during weighted elbow flexion-extension movement when both the old and young groups maintain the same performance level. In particular, overactivation of the basal ganglia in the aging brain appears to play a crucial role in counteracting age-related decline of force generation and to support the same level of performance as that of younger counterparts.