With advancing age comes a decline in voluntary movement control. Growing evidence suggests that an age-related decline in effective connectivity between the supplementary motor area and primary motor cortex (SMA-M1) might play a role in an age-related decline of bilateral motor control. Dual-site transcranial magnetic stimulation (TMS) can be used to measure SMA-M1 effective connectivity. In the current study, we aimed to (1) replicate previous dual-site TMS research showing reduced SMA-M1 connectivity in older than younger adults and (2) examine whether SMA-M1 connectivity is associated with bilateral motor control in independent samples of younger (n = 30) and older adults (n = 30). SMA-M1 connectivity was measured using dual-site TMS with interstimulus intervals of 6, 7 and 8 ms, and bilateral motor control was measured using the Purdue Pegboard, Four Square Step Test and the Timed Up and Go task. Findings from this study showed that SMA-M1 connectivity was reduced in older than in younger adults, suggesting that the direct excitatory connections between SMA and M1 had reduced efficacy in older than younger adults. Furthermore, greater SMA-M1 connectivity was associated with better bimanual motor control in older adults. Thus, SMA-M1 connectivity in older adults might underpin, in part, the age-related decline in bilateral motor control. These findings contribute to our understanding of age-related declines in motor control and provide a physiological basis for the development of interventions to improve bimanual and bilateral motor control.

中文翻译：

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使用双站点 TMS 测量的老年人比年轻人的 SMA-M1 连通性降低

随着年龄的增长，自主运动控制能力下降。越来越多的证据表明，辅助运动区和初级运动皮层 (SMA-M1) 之间有效连接的年龄相关性下降可能在双侧运动控制的年龄相关性下降中起作用。双站点经颅磁刺激 (TMS) 可用于测量 SMA-M1 的有效连通性。在当前的研究中，我们的目标是 (1) 复制先前的双站点 TMS 研究，显示老年人的 SMA-M1 连接性比年轻人低，(2) 检查 SMA-M1 连接性是否与年轻人的独立样本中的双侧运动控制有关。 ( n  = 30) 和老年人 ( n = 30）。SMA-M1 连通性使用双站点 TMS 测量，刺激间隔为 6、7 和 8 ms，双边运动控制使用 Purdue Pegboard、四方步测试和 Timed Up and Go 任务测量。这项研究的结果表明，老年人的 SMA-M1 连接性比年轻人低，这表明 SMA 和 M1 之间的直接兴奋性连接对老年人的疗效比年轻人低。此外，更大的 SMA-M1 连接与老年人更好的双手运动控制有关。因此，老年人的 SMA-M1 连接可能在一定程度上支持双侧运动控制与年龄相关的下降。