Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia, Genoa, Italy.
J Neurophysiol. 2012 Jun;107(12):3433-45. doi: 10.1152/jn.00420.2011. Epub 2012 Mar 21.
When submitted to a visuomotor rotation, subjects show rapid adaptation of visually guided arm reaching movements, indicated by a progressive reduction in reaching errors. In this study, we wanted to make a step forward by investigating to what extent this adaptation also implies changes into the motor plan. Up to now, classical visuomotor rotation paradigms have been performed on the horizontal plane, where the reaching motor plan in general requires the same kinematics (i.e., straight path and symmetric velocity profile). To overcome this limitation, we considered vertical and horizontal movement directions requiring specific velocity profiles. This way, a change in the motor plan due to the visuomotor conflict would be measurable in terms of a modification in the velocity profile of the reaching movement. Ten subjects performed horizontal and vertical reaching movements while observing a rotated visual feedback of their motion. We found that adaptation to a visuomotor rotation produces a significant change in the motor plan, i.e., changes to the symmetry of velocity profiles. This suggests that the central nervous system takes into account the visual information to plan a future motion, even if this causes the adoption of nonoptimal motor plans in terms of energy consumption. However, the influence of vision on arm movement planning is not fixed, but rather changes as a function of the visual orientation of the movement. Indeed, a clear influence on motion planning can be observed only when the movement is visually presented as oriented along the vertical direction. Thus vision contributes differently to the planning of arm pointing movements depending on motion orientation in space.
当被置于视动旋转中时，被试者的视觉引导手臂运动表现出快速的适应，这表现为手臂运动的误差逐渐减少。在这项研究中，我们希望更进一步，探究这种适应在多大程度上也意味着运动计划的改变。到目前为止，经典的视动旋转范式都是在水平面上进行的，在这个平面上，手臂运动计划通常需要相同的运动学（即直线路径和对称速度分布）。为了克服这一限制，我们考虑了垂直和水平运动方向，这些方向需要特定的速度分布。这样，由于视动冲突导致的运动计划的改变就可以通过测量手臂运动的速度分布的改变来衡量。十名被试者在观察到他们运动的旋转视觉反馈的情况下，进行了水平和垂直的手臂运动。我们发现，对视动旋转的适应会导致运动计划的显著改变，即速度分布的对称性改变。这表明中枢神经系统会考虑视觉信息来规划未来的运动，即使这会导致采用非最优的运动计划，从而增加能量消耗。然而，视觉对手臂运动规划的影响并不是固定的，而是随着运动的视觉方向而变化。事实上，只有当运动在视觉上呈现为沿垂直方向定向时，才能观察到对运动规划的明显影响。因此，视觉对视动旋转中手臂指向运动规划的贡献取决于运动在空间中的方向。
