Neuroscience Research Australia, Randwick, New South Wales, 2031, Australia.
University of New South Wales, Kensington, New South Wales, 2032, Australia.
J Physiol. 2019 Dec;597(24):5973-5984. doi: 10.1113/JP278630. Epub 2019 Nov 28.
How we judge the location of our body parts can be affected by a range of factors that change how our brain interprets proprioceptive signals. We examined the effect of several such factors on how we perceive an object's width and the spacing between our thumb and fingers when grasping. Grasp-related perceptions were slightly wider when using all digits, in line with our tendency to grasp larger objects with the entire hand. Surprisingly, these perceptions were not affected by the frames of reference for judgements (object width versus grasp aperture), whether the object was grasped actively or passively, or the strength of the grasp. These results show that the brain maintains a largely stable representation of the hand when grasping stationary objects. This stability may underpin our dexterity when grasping a vast array of objects.
Various factors can alter how the brain interprets proprioceptive signals, leading to errors in how we perceive our body and execute motor tasks. This study determined the effect of critical factors on hand-based perceptions. In Experiment 1, 20 participants grasped without lifting an unseen 6.5 cm-wide object with two grasp configurations: thumb and all fingers, and thumb and index finger. Participants reported perceived grasp aperture (body reference frame) or perceived object width (external reference frame) using visual charts. In Experiment 2, 20 participants grasped the object with three grasp intensities (1, 5 and 15% maximal grasp force) actively or passively and reported perceived grasp aperture. A follow-up experiment addressed whether results from Experiment 2 were influenced by the external force applied during passive grasp. Overall, there was a mean difference of 0.38 cm (95% confidence interval (CI), 0.12 to 0.63) between the two grasp configurations (all digits compared to thumb and index finger). Perceived object width compared to perceived grasp aperture differed by only -0.04 cm (95% CI, -0.30 to 0.21). There was no real effect of grasp intensity on perceived grasp aperture (-0.01 cm; 95% CI, -0.03 to 0.01) or grasp type (active versus passive; 0.18 cm; 95% CI, -0.19 to 0.55). Overall, grasp-related perceptions are slightly wider when using all digits, in line with our tendency to grasp larger objects with the entire hand. The other factors - frame of reference, grasp intensity and grasp type - had no meaningful effect on these perceptions. These results provide evidence that the brain maintains a largely stable representation of the hand.
我们判断身体部位位置的方式可能会受到一系列因素的影响，这些因素会改变大脑对本体感觉信号的解读。我们研究了这些因素中的几个因素对我们感知物体宽度以及拇指和手指之间抓握间距的影响。使用所有手指抓握时，感知到的抓握宽度会稍宽一些，这与我们用整个手抓握较大物体的倾向一致。令人惊讶的是，这些感知不受判断的参照系（物体宽度与抓握开口度）、物体是主动抓握还是被动抓握以及抓握强度的影响。这些结果表明，大脑在抓握静止物体时对手的位置保持着基本稳定的表示。这种稳定性可能是我们在抓握各种物体时灵巧性的基础。
各种因素会改变大脑对本体感觉信号的解读，从而导致我们对身体的感知和执行运动任务出现错误。本研究确定了关键因素对手部感知的影响。在实验 1 中，20 名参与者在不抬起看不见的 6.5 厘米宽物体的情况下，使用两种抓握配置（拇指和所有手指，以及拇指和食指）进行抓握。参与者使用视觉图表报告感知到的抓握开口度（身体参照系）或感知到的物体宽度（外部参照系）。在实验 2 中，20 名参与者主动或被动地以三种抓握强度（1%、5%和 15%最大抓握力）抓握物体，并报告感知到的抓握开口度。后续实验探讨了实验 2 中的结果是否受到被动抓握时施加的外力的影响。总的来说，两种抓握配置（所有手指与拇指和食指相比）之间存在 0.38 厘米的平均差异（95%置信区间（CI），0.12 至 0.63）。感知到的物体宽度与感知到的抓握开口度相差仅-0.04 厘米（95%CI，-0.30 至 0.21）。抓握强度（0.01 厘米；95%CI，-0.03 至 0.01）或抓握类型（主动与被动；0.18 厘米；95%CI，-0.19 至 0.55）对感知到的抓握开口度没有真正的影响。总的来说，使用所有手指抓握时，感知到的抓握宽度会稍宽一些，这与我们用整个手抓握较大物体的倾向一致。其他因素——参照系、抓握强度和抓握类型——对这些感知没有明显影响。这些结果提供了证据表明，大脑对手的位置保持着基本稳定的表示。
