Characteristics of Handwriting Motion and Indicators of Dexterity

本研究旨在寻找能区分正常人左手手笔迹和偏瘫患者左右手笔迹的三维参数。受试者在三个不同大小的正方形中书写一个日语音节字符，然后，他们用同样的三个不同大小的正方形描绘同一个日语字符。计算了书写字符的时间、书写字符的长度、与加速度和加加速度相关的参数、笔尖直径、食指根部直径和手腕轨迹。食指直径与手腕轨迹的比值分别定义为食指直径与手腕轨迹的比值除以笔尖轨迹的比值。当该比值接近零时，笔尖比手指或手腕运动更活跃，表明拇指和手指具有独立/灵巧的书写运动能力。正常受试者的字体越大，笔尖速度越快。因此，书写字符的时间保持不变。从笔尖的加速度和加加速度导出的参数显示在一些患者中的手写运动不平滑。书写文字长度除以字径，部分感觉障碍患者字线晃动或冗余。无论书写还是描记，左手的轨迹尺寸比例大于右手，大尺寸的轨迹尺寸比例大于小尺寸的轨迹尺寸比例。换句话说，用右手书写或描绘一个小的或正常大小的字符是很好的习得和熟练的。在无感觉障碍的右利手偏瘫患者中，尽管右手书写和描记的速度比左手慢，但该比率与正常人相似。

This study was intended to find three-dimensional parameters of handwriting which could discriminate handwriting with the right from left hand in the normal subjects and show handwriting characteristics in the patients with hemiparesis. Participants wrote a Japanese syllabary character in squares of three different sizes as they normally would write it. Then, they trace the same Japanese character of the same three different sizes. The time to write a character, length of the written character, the parameters related with acceleration and jerk, the diameter of the pen-tip, index finger base, and the wrist trajectories were computed. The ratios of the diameter of the index finger and the wrist trajectories were defined respectively as those divided by that of the pen-tip trajectory. When the ratio is near zero, the pen tip moves more actively than the finger or wrist indicating capability of independent/dexterous movement of the thumb and fingers for handwriting.The larger the character size, the faster the pen-tip speed in the normal subjects. Thus, the time to write a character was kept constant. Parameters derived from acceleration and jerk of the pen tip showed unsmooth movement of handwriting in some patients. The length of the written character divided by the character diameter showed sway or redundancy of the lines of the character in some patients with sensory disturbance. Regardless of writing or tracing, the ratio of the trajectory size for the left hand was larger than that for the right, and that for the larger size than that for the smaller. In other words, writing or tracing a small or regular-sized character with the right hand is well-acquired and proficient. In the right-handed hemiparetic patients without sensory disturbance, the ratio was similar to that in the normal subjects even though writing and tracing with the right hand were slower those with the left.