ORCID Profile
0000-0002-1000-529X
Current Organisation
KU Leuven
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Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.CORTEX.2016.02.007
Abstract: Even though it has been suggested that the dorsolateral prefrontal cortex (DLPFC) and dorsal premotor cortex (PMd) are highly involved in the planning of bimanual movements, the exact nature (facilitatory or inhibitory) of their role is not well understood. Using a dual-site transcranial magnetic stimulation (TMS) paradigm, we examined the functional influence from DLPFC and PMd to the contralateral primary cortex (M1) during the preparation of a complex bimanual coordination task in which inter-hand movement frequency was manipulated. Only the left PMd showed inter-hand frequency-specific modulations in the interaction with the contralateral M1. Left PMd-right M1 interaction became facilitatory during the preparation phase when the left hand had to move faster than the right hand, while inhibitory modulation was observed when the movement frequency arrangement was reversed. Interestingly, bilateral DLPFC showed a facilitatory interaction with the contralateral M1s during the preparation period only in difficult conditions, irrespective of the inter-hand frequency ratio, suggesting a less task-specific role in the organization of complex bimanual actions. Observed task-related modulations in DLPFC-M1 and left PMd-right M1 interactions during preparation were significantly correlated with up-coming performance, predicting successful bimanual movements. These observations highlight the distinct roles of DLPFC and left PMd in the preparation of bimanual movements that require a differential contribution of each limb.
Publisher: Society for Neuroscience
Date: 10-02-2016
DOI: 10.1523/JNEUROSCI.3355-15.2016
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. SIGNIFICANCE STATEMENT 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.
No related grants have been discovered for Guy Rens.