Perceptual Motor Behaviour Laboratory, Centre for Motor Control, Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada.
J Neurophysiol. 2022 Sep 1;128(3):681-688. doi: 10.1152/jn.00236.2022. Epub 2022 Aug 10.
Our perception of sensory events can be altered by action, but less is known about how our perception can be altered by action observation. For example, our ability to detect tactile stimuli is reduced when our limb is moving, and task-relevance and movement speed can alter such tactile detectability. During action observation, however, the relationship between tactile processing and such modulating factors is not known. Thus, the current study sought to explore tactile processing at a task-relevant location during the observation of reaching and grasping movements performed at different speeds. Specifically, participants observed videos of an anonymous model performing movements at a slow [i.e., peak velocity (PV): 155 mm/s], medium (i.e., PV: 547 mm/s), or fast speed (i.e., PV: 955 mm/s). To assess tactile processing, weak electrical stimuli of different amplitudes were presented to participants' right thumbs when the observed model was at their starting position and prior to any movement, or when the observed model's limb reached its PV. When observing slow movements, normalized perceptual thresholds were significantly lower/better than for the premovement stimulation time. These data suggest that the movement speed can modulate tactile processing, even when observing a movement. Furthermore, these findings provide seminal evidence for tactile facilitation at a task-relevant location during the observation of slow reaching and grasping movements (i.e., speeds associated with tactile exploration). Previous work has highlighted the relationship between touch processing and movement speed during action, but the current study sought to understand this relationship during action observation of reaching and grasping movements. Here, we provide seminal evidence that tactile perceptual thresholds at the thumb are reduced compared with rest when observing the slowest movement speeds. Thus, tactile processing was facilitated at a task-relevant location during the observation of movements with speeds associated with tactile exploration.
我们对感觉事件的感知可以通过行动来改变，但对于我们的感知如何通过观察行动来改变，了解较少。例如，当我们的肢体移动时，我们检测触觉刺激的能力会降低，而任务相关性和运动速度可以改变这种触觉可检测性。然而，在观察行动时，尚不清楚触觉处理与这些调节因素之间的关系。因此，当前的研究旨在探索在观察以不同速度进行的伸手和抓握运动时，在任务相关位置的触觉处理。具体而言，参与者观看了一个匿名模特以慢（即峰值速度 (PV)：155 毫米/秒）、中（即 PV：547 毫米/秒）或快（即 PV：955 毫米/秒）速度进行运动的视频。为了评估触觉处理，当观察到的模型处于起始位置且在进行任何运动之前，或者当观察到的模型的肢体达到其 PV 时，向参与者的右手拇指施加不同幅度的弱电流刺激。当观察缓慢运动时，与运动前刺激时间相比，归一化感知阈值明显更低/更好。这些数据表明，即使在观察运动时，运动速度也可以调节触觉处理。此外，这些发现为在观察缓慢伸手和抓握运动（即与触觉探索相关的速度）时在任务相关位置提供触觉促进提供了开创性的证据。以前的工作强调了在行动中触摸处理与运动速度之间的关系，但当前的研究旨在理解在伸手和抓握运动的观察行动中这种关系。在这里，我们提供了开创性的证据，即在观察最慢运动速度时，拇指的触觉感知阈值与休息时相比降低。因此，在与触觉探索相关的速度下进行运动观察时，在任务相关位置促进了触觉处理。
