title: Age-Related Changes in Frontal Network Structural and Functional Connectivity in Relation to Bimanual Movement Control.
abstract: Changes in both brain structure and neurophysiological function regulating homotopic as well as heterotopic interhemispheric interactions (IHIs) are assumed to be responsible for the bimanual performance deficits in older adults. However, how the structural and functional networks regulating bimanual performance decline in older adults, as well as the interplay between brain structure and function remain largely unclear. Using a dual-site transcranial magnetic stimulation paradigm, we examined the age-related changes in the interhemispheric effects from the dorsolateral prefrontal cortex and dorsal premotor cortex onto the contralateral primary motor cortex (M1) during the preparation of a complex bimanual coordination task in human. Structural properties of these interactions were assessed with diffusion-based fiber tractography. Compared with young adults, older adults showed performance declines in the more difficult bimanual conditions, less optimal brain white matter (WM) microstructure, and a decreased ability to regulate the interaction between dorsolateral prefrontal cortex and M1. Importantly, we found that WM microstructure, neurophysiological function, and bimanual performance were interrelated in older adults, whereas only the task-related changes in IHI predicted bimanual performance in young adults. These results reflect unique interactions between structure and function in the aging brain, such that declines in WM microstructural organization likely lead to dysfunctional regulation of IHI, ultimately accounting for bimanual performance deficits.
  
  
  CONCLUSIONS
  The structural and functional changes in the aging brain are associated with a decline in movement control, compromising functional independence. We used MRI and noninvasive brain stimulation techniques to investigate white matter microstructural organization and neurophysiological function in the aging brain, in relation to bimanual movement control. We found that less optimal brain microstructural organization and task-related modulations in neurophysiological function resulted in poor bimanual performance in older adults. By interrelating brain structure, neurophysiological function, and behavior, the current study provides a comprehensive picture of biological alterations in the aging brain that underlie declines in bimanual performance.
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and Hak.Fujiyama@faber.kuleuven.be.
authors: Hakuei
authors: http://orcid.org/0000-0001-9764-5398
authors: H
authors: Fujiyama
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and.
authors: Jago
authors: J
authors: Van Soom
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and.
authors: Guy
authors: G
authors: Rens
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and.
authors: Jolien
authors: J
authors: Gooijers
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and.
authors: Inge
authors: http://orcid.org/0000-0002-3977-3620
authors: I
authors: Leunissen
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and.
authors: Oron
authors: O
authors: Levin
authors: Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, 3001, Leuven, Belgium, and Leuven Research Institute for Neuroscience and Disease, 3001, Leuven, Belgium.
authors: Stephan P
authors: SP
authors: Swinnen
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D066127:White Matter / Q000033:anatomy & histology / Q000502:physiology; D055815:Young Adult
keywords: MRI; aging; bimanual coordination; interhemispheric communication; transcranial magnetic stimulation