Centre for Vision Research, York University, Toronto, Canada.
Exp Brain Res. 2013 Jul;228(3):313-25. doi: 10.1007/s00221-013-3564-7. Epub 2013 May 26.
Reaching to targets with misaligned visual feedback of the hand leads to changes in proprioceptive estimates of hand position and reach aftereffects. In such tasks, subjects are able to make use of two error signals: the discrepancy between the desired and actual movement, known as the sensorimotor error signal, and the discrepancy between visual and proprioceptive estimates of hand position, which we refer to as the cross-sensory error signal. We have recently shown that mere exposure to a sensory discrepancy in the absence of goal-directed movement (i.e. no sensorimotor error signal) is sufficient to produce similar changes in felt hand position and reach aftereffects. Here, we sought to determine the extent that this cross-sensory error signal can contribute to proprioceptive recalibration and movement aftereffects by manipulating the magnitude of this signal in the absence of volitional aiming movements. Subjects pushed their hand out along a robot-generated linear path that was gradually rotated clockwise relative to the path of a cursor. On all trials, subjects viewed a cursor that headed directly towards a remembered target while their hand moved out synchronously. After exposure to a 30° rotated hand-cursor distortion, subjects recalibrated their sense of felt hand position and adapted their reaches. However, no additional increases in recalibration or aftereffects were observed following further increases in the cross-sensory error signal (e.g. up to 70°). This is in contrast to our previous study where subjects freely reached to targets with misaligned visual hand position feedback, hence experiencing both sensorimotor and cross-sensory errors, and the distortion magnitude systematically predicted increases in proprioceptive recalibration and reach aftereffects. Given these findings, we suggest that the cross-sensory error signal results in changes to felt hand position which drive partial reach aftereffects, while larger aftereffects that are produced after visuomotor adaptation (and that vary with the size of distortion) are related to the sensorimotor error signal.
当手的视觉反馈与目标不匹配时，会导致对手部位置的本体感受估计和伸手后效发生变化。在这类任务中，被试可以利用两种错误信号：期望运动与实际运动之间的差异，称为运动感觉错误信号；视觉和本体感受对手部位置的估计之间的差异，我们称之为跨感觉错误信号。我们最近发现，即使在没有目标导向运动的情况下（即没有运动感觉错误信号），仅仅暴露于感觉差异中也足以引起手部感觉位置和伸手后效的类似变化。在这里，我们试图通过在没有意愿性瞄准运动的情况下操纵该信号的幅度来确定这种跨感觉错误信号对本体感受再校准和运动后效的贡献程度。被试沿着机器人产生的线性路径推动手，该路径相对于光标路径逐渐顺时针旋转。在所有试验中，被试看到一个光标，它直接朝向一个记忆中的目标，而他们的手同步移动。在经历了 30°的手光标旋转失真后，被试对手部感觉位置进行了重新校准并适应了伸手。然而，在进一步增加跨感觉错误信号（例如，高达 70°）后，没有观察到再校准或后效的额外增加。这与我们之前的研究形成了对比，在之前的研究中，被试自由地伸手去够与视觉手位置反馈不匹配的目标，因此经历了运动感觉和跨感觉错误，并且失真程度系统地预测了本体感受再校准和伸手后效的增加。鉴于这些发现，我们认为跨感觉错误信号会导致感觉手部位置的变化，从而产生部分伸手后效，而较大的后效是在视动适应后产生的（并且随失真程度而变化），这与运动感觉错误信号有关。
