Takei Y, Grasso R, Amorim M A, Berthoz A
Laboratoire de Physiologie de la Perception et de l'Action, CNRS-Collège de France, Paris.
Exp Brain Res. 1997 Jun;115(2):361-8. doi: 10.1007/pl00005705.
Eight healthy subjects were asked to walk blindfolded along circular paths of different radii after several practice trials with vision. Their task was to stop after completing two full revolutions. They always walked counter-clockwise (CCW) in (a) a control condition (CONTROL), including the instructions mentioned above, (b) with the further instruction to count backwards in twos (MENTAL), (c) with the instruction to count loudly (LOUD). The movement of two markers lying along the head naso-occipital axis was recorded by means of an ELITE system. Total walked distance (DISTANCE), total head turning angle (ANGLE) and average radius (RADIUS) of the trajectories performed were measured. All subjects were able to perform approximately circular trajectories. They consistently overshot the ideal radius independently of the condition and circle size, undershot the total angle and overshot total distance. The LOUD condition induced greater errors in the performance but only on total distance (P<0.05). A strong correlation was found between the errors in radius and total distance but not between distance and total angle. Principal components analysis suggested that radius and distance share a common source of errors while total angle produced independent errors. The results indicate that (a) circular trajectories can be generated starting from spatial and/or motor memory, without the aid of visual information; (b) the task needs some attentional control and does not involve simple automatic processing of afferent information; (c) different sensory information or different processing modes are probably involved in the estimation of the curvature and length of the walked path on the one hand, and of the total rotation angle on the other.
八名健康受试者在进行了几次有视觉参与的练习试验后，被要求蒙着眼睛沿着不同半径的圆形路径行走。他们的任务是在完成两整圈后停下。他们总是逆时针（CCW）行走，（a）在一种控制条件下（CONTROL），包括上述指令，（b）另外被要求每隔一个数倒着数（MENTAL），（c）被要求大声数数（LOUD）。借助ELITE系统记录了沿头部鼻枕轴放置的两个标记的运动。测量了行走的总距离（DISTANCE）、头部转动的总角度（ANGLE）以及所走轨迹的平均半径（RADIUS）。所有受试者都能够走出大致圆形的轨迹。他们始终会偏离理想半径（与条件和圆的大小无关），未达到总角度，且超过了总距离。大声数数（LOUD）条件下的表现产生了更大的误差，但仅在总距离方面（P<0.05）。发现半径误差和总距离误差之间存在很强的相关性，但距离和总角度之间不存在相关性。主成分分析表明，半径和距离存在共同的误差来源，而总角度产生独立的误差。结果表明：（a）无需视觉信息辅助，可从空间和/或运动记忆出发生成圆形轨迹；（b）该任务需要一定的注意力控制，不涉及传入信息的简单自动处理；（c）一方面，在估计行走路径的曲率和长度时，另一方面，在估计总旋转角度时，可能涉及不同的感觉信息或不同的处理模式。
