Yoles-Frenkel Michal, Avron Maayan, Prut Yifat
Department of Medical Neurobiology, Institute of Medical Research Israel-Canada, Edmond and Lily Safra Center for Brain Research, The Hebrew University Jerusalem, Israel.
Front Integr Neurosci. 2016 Jan 19;10:1. doi: 10.3389/fnint.2016.00001. eCollection 2016.
The auditory and motor systems are strongly coupled, as is evident in the specifically tight motor synchronization that occurs in response to regularly occurring auditory cues compared with cues of other modalities. Timing of rhythmic action is known to rely on multiple neural centers including the cerebellum and the basal-ganglia which have access to both motor cortical and spinal circuitries. To date, however, there is little information on the motor mechanisms that operate during preparation and execution of rhythmic vs. non-rhythmic movements. We measured acceleration profile and muscle activity while subjects performed tapping movements in response to auditory cues. We found that when tapping at random intervals there was a higher variability of both acceleration profile and muscle activity during motor preparation compared to rhythmic tapping. However, the specific rhythmic context (cued, self-paced, or syncopation) did not affect the motor parameters of the executed taps. Finally, during entrainment we found a gradual as opposed to episodic change in low-level motor parameters (i.e., preparatory muscle activity) that was strongly correlated with changes in high-level parameters (i.e., shift in the reaction time to negative asynchrony). These findings suggest that motor entrainment involves not only adjusting the timing of movement but also modifying parameters that are related to its production. These changes in motor output were insensitive to the specifics of the rhythmic cue: although it took subjects different times to become entrained to different types of rhythmic cues, the motor actions produced once entrainment was obtained were indistinguishable. These findings suggest that motor entrainment involves not only adjusting the timing of movement but also modifying parameters related to its production. The reduced variability of muscle activity during the preparatory period could be one mechanism used by the motor system to enhance the accuracy of motor timing.
听觉系统和运动系统紧密耦合,这在以下方面表现得很明显:与其他感觉模态的提示相比,对有规律出现的听觉提示做出反应时会出现特别紧密的运动同步。已知有节奏动作的时间安排依赖于多个神经中枢,包括小脑和基底神经节,它们可以接入运动皮层和脊髓回路。然而,迄今为止,关于有节奏运动与无节奏运动的准备和执行过程中起作用的运动机制的信息很少。我们在受试者根据听觉提示进行敲击动作时测量了加速度曲线和肌肉活动。我们发现,与有节奏的敲击相比,当以随机间隔进行敲击时,运动准备期间加速度曲线和肌肉活动的变异性更高。然而特定的节奏背景(提示的、自我节奏的或切分节奏的)并不影响所执行敲击的运动参数。最后,在同步化过程中,我们发现低水平运动参数(即准备性肌肉活动)是逐渐变化而非突然变化的,这与高水平参数的变化(即反应时间向负异步的转变)密切相关。这些发现表明,运动同步化不仅涉及调整运动时间,还涉及修改与其产生相关的参数。运动输出的这些变化对节奏提示的具体细节不敏感:尽管受试者达到不同类型节奏提示同步化所需的时间不同,但一旦实现同步化所产生的运动动作却难以区分。这些发现表明,运动同步化不仅涉及调整运动时间,还涉及修改与其产生相关的参数。准备期肌肉活动变异性的降低可能是运动系统用于提高运动时间准确性的一种机制。