School of Kinesiology, University of Michigan, Ann Arbor, MI 48109-2214, USA.
Cereb Cortex. 2012 Nov;22(11):2643-52. doi: 10.1093/cercor/bhr349. Epub 2011 Dec 12.
Bimanual actions involve coordinated motion but often rely on the movements performed with each hand to be different. Older adults exhibit differentially greater variability for bimanual actions in which each hand has an independent movement goal. Such actions rely on interhemispheric communication via the corpus callosum, including both facilitatory and inhibitory interactions. Here, we investigated whether age differences in callosal structure and interhemispheric function contribute to this selective movement difficulty. Participants performed 3 force production tasks: 1) unimanual, 2) bimanual simultaneous, and 3) bimanual independent. Older adults had significantly greater interhemispheric facilitation during voluntary muscle activation. We also report a fundamental shift with age in the relationship between callosal tract microstructural integrity and interhemispheric inhibition (IHI). Specifically, older adults with relatively greater callosal tract microstructural integrity have less IHI. Furthermore, greater IHI was related to poorer bimanual performance (assessed by dominant hand force variability) in older adults on all tasks, whereas this relationship was only observed in young adults for the bimanual independent condition. These findings indicate changes in interhemispheric communication with advancing age such that older adults may rely on bilateral cortical cooperation to a greater extent than young adults for manual actions.
双手动作涉及协调运动，但通常依赖于双手的运动是不同的。老年人在双手具有独立运动目标的双手动作中表现出更大的变异性。这种动作依赖于胼胝体的大脑两半球间的通讯，包括促进和抑制的相互作用。在这里，我们研究了胼胝体结构和大脑两半球间功能的年龄差异是否有助于这种选择性运动困难。参与者执行了 3 项力量产生任务：1）单手，2）双手同时，3）双手独立。老年人在自愿肌肉激活过程中表现出明显更大的大脑两半球间的促进作用。我们还报告了大脑两半球间抑制（IHI）与胼胝体束微观结构完整性之间的关系随着年龄的变化。具体而言，胼胝体束微观结构完整性相对较大的老年人的 IHI 较少。此外，在所有任务中，较大的 IHI 与老年人的双手动作（用优势手力的变异性来评估）较差相关，而这种关系仅在年轻人的双手独立条件下观察到。这些发现表明，随着年龄的增长，大脑两半球间的通讯发生了变化，因此老年人可能比年轻人更依赖双侧皮质合作来进行手动操作。
