Specific neural mechanisms operate at corticospinal levels during eccentric and concentric contractions. Here, we investigated the difference in corticospinal excitability (CSE) when preparing these two types of contraction. In this study we enrolled 16 healthy participants. They were asked to perform an instructed-delay reaction time (RT) task involving a concentric or an eccentric contraction of the right first dorsal interosseus muscle, as a response to a proprioceptive cue (Go signal) presented 1 s after a warning signal. We tested CSE at different time points ranging from 300 ms before up to 40 ms after a Go signal. CSE increased 300–150 ms before the Go signal for both contractions. Interestingly, significant changes in CSE in the time interval around the Go signal (from −150 ms to +40 ms) were only revealed in eccentric contraction. We observed a significant decrease in excitability immediately before the Go cue (Pre_50) and a significant increase 40 ms after it (Post_40) with respect to the MEPs recorded at Pre_150. Finally, CSE in eccentric contraction was lower before the Go cue (Pre_50) and greater after it (Post_40) compared to the concentric contraction. A similar result was also found in NoMov paradigm, used to disentangle the effects induced by movement preparation from those induced by the movement preparation linked to the proprioceptive cue. We could conclude that different neural mechanisms observed during concentric and eccentric contractions are mirrored with a different time-specific modulation of CSE in the preparatory phase to the movement.

在离心和向心收缩期间，特定的神经机制在皮质脊髓水平起作用。在这里，我们研究了准备这两种收缩时皮质脊髓兴奋性 (CSE) 的差异。在这项研究中，我们招募了 16 名健康参与者。他们被要求执行一项指令延迟反应时间 (RT) 任务，涉及右侧第一背骨间肌的向心或离心收缩，作为对警告信号后 1 秒呈现的本体感觉提示（Go 信号）的反应。我们在不同时间点测试了 CSE，范围从 Go 信号前 300 毫秒到 Go 信号后 40 毫秒不等。CSE 在两次收缩的 Go 信号之前增加 300-150 毫秒。有趣的是，在 Go 信号周围的时间间隔（从 -150 毫秒到 +40 毫秒）中，CSE 的显着变化仅在离心收缩中显示出来。与在 Pre_150 记录的 MEP 相比，我们观察到在 Go 提示 (Pre_50) 之前的兴奋性显着降低，并且在它 (Post_40) 之后 40 毫秒显着增加。最后，与同心收缩相比，偏心收缩中的 CSE 在 Go 提示 (Pre_50) 之前较低，之后 (Post_40) 更高。在 NoMov 范式中也发现了类似的结果，用于将运动准备引起的影响与与本体感受线索相关的运动准备引起的影响分开。我们可以得出结论，在向心和离心收缩期间观察到的不同神经机制与运动准备阶段的 CSE 的不同时间特定调制相反映。