Bakker Romy S, Weijer Roel H A, van Beers Robert J, Selen Luc P J, Medendorp W Pieter
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; and
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; and.
J Neurophysiol. 2017 Jun 1;117(6):2250-2261. doi: 10.1152/jn.00022.2017. Epub 2017 Mar 1.
In everyday life, we frequently have to decide which hand to use for a certain action. It has been suggested that for this decision the brain calculates expected costs based on action values, such as expected biomechanical costs, expected success rate, handedness, and skillfulness. Although these conclusions were based on experiments in stationary subjects, we often act while the body is in motion. We investigated how hand choice is affected by passive body motion, which directly affects the biomechanical costs of the arm movement due to its inertia. With the use of a linear motion platform, 12 right-handed subjects were sinusoidally translated (0.625 and 0.5 Hz). At 8 possible motion phases, they had to reach, using either their left or right hand, to a target presented at 1 of 11 possible locations. We predicted hand choice by calculating the expected biomechanical costs under different assumptions about the future acceleration involved in these computations, being the forthcoming acceleration during the reach, the instantaneous acceleration at target onset, or zero acceleration as if the body were stationary. Although hand choice was generally biased to use of the dominant hand, it also modulated sinusoidally with the motion, with the amplitude of the bias depending on the motion's peak acceleration. The phase of hand choice modulation was consistent with the cost model that took the instantaneous acceleration signal at target onset. This suggests that the brain relies on the bottom-up acceleration signals, and not on predictions about future accelerations, when deciding on hand choice during passive whole body motion. Decisions of hand choice are a fundamental aspect of human behavior. Whereas these decisions are typically studied in stationary subjects, this study examines hand choice while subjects are in motion. We show that accelerations of the body, which differentially modulate the biomechanical costs of left and right hand movements, are also taken into account when deciding which hand to use for a reach, possibly based on bottom-up processing of the otolith signal.
在日常生活中，我们经常需要决定用哪只手来执行某个动作。有人提出，对于这个决策，大脑会根据动作价值计算预期成本，比如预期的生物力学成本、预期成功率、用手习惯和熟练程度。尽管这些结论是基于对静止受试者的实验得出的，但我们在身体运动时也会行动。我们研究了被动身体运动如何影响手的选择，被动身体运动因其惯性会直接影响手臂运动的生物力学成本。通过使用线性运动平台，对12名右利手受试者进行正弦平移（频率为0.625和0.5赫兹）。在8个可能的运动阶段，他们必须用左手或右手伸向11个可能位置之一出现的目标。我们通过在关于这些计算中涉及的未来加速度的不同假设下计算预期生物力学成本来预测手的选择，这些假设包括伸手过程中的即将到来的加速度、目标出现时的瞬时加速度，或者如同身体静止时的零加速度。尽管手的选择通常倾向于使用优势手，但它也会随着运动呈正弦调制，偏差的幅度取决于运动的峰值加速度。手的选择调制的相位与采用目标出现时瞬时加速度信号的成本模型一致。这表明，在被动全身运动过程中决定手的选择时，大脑依赖自下而上的加速度信号，而不是对未来加速度的预测。手的选择决策是人类行为的一个基本方面。虽然这些决策通常在静止受试者中进行研究，但本研究考察了受试者在运动时的手的选择。我们表明，身体的加速度会不同程度地调节左右手动的生物力学成本，在决定伸手用哪只手时也会被考虑在内，这可能是基于耳石信号的自下而上的处理。
