The effect of passive whole-body translation on corticospinal excitability for hand selection

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Decisions of hand choice for an action depends on whether the body is stationary or in motion. Recently, it has been shown that during lateral sinusoidal motion of the body, there is a bias to choose the right hand for leftward acceleration, which reverses to the left hand for rightward acceleration. Furthermore, this bias disappears at zero acceleration, when the body moves at maximum velocity. The neural correlates underlying these observations have not been studied. Here, using single-pulse TMS, we investigated the excitability of left M1 during a hand selection task under passive whole-body translations, imposed by a vestibular sled. Given these preferences for hand choices during motion, we expected that the excitability of left M1 would be increased for leftward accelerations, decreased for rightward accelerations, and unchanged at maximum velocity. We measured the peak-to-peak amplitude of the motor evoked potential (MEP) from the lateral triceps of the right arm using surface electromyography (EMG) at eight fixed phases of the sinusoidal whole-body translation. Results showed that MEP amplitude modulates with the whole-body motion, with the highest MEP amplitude when the body was at increasing leftward acceleration (phase 45º). A sinusoidal relationship between MEP amplitude and phase of motion outperformed a phase-independent relationship. In summary, our data suggest that passive whole-body acceleration affects corticospinal excitability, thereby biasing upcoming hand choices in an acceleration dependent manner.
Faculteit der Sociale Wetenschappen