Characteristics of Handwriting Motion and Indicators of Dexterity

本研究旨在寻找能够区分正常人右手和左手笔迹，并显示偏瘫患者笔迹特征的笔迹三维参数。参与者在三个不同大小的方块中写下了一个日语音节字符，这是他们通常会写的。然后，他们追踪相同的三个不同大小的相同日语字符。计算书写字符的时间、书写字符的长度、与加速度和挺举有关的参数、笔尖直径、食指根部和手腕轨迹。食指直径和手腕轨迹的比值分别定义为笔尖轨迹的比值。当比率接近零时，笔尖的移动比手指或手腕更活跃，表明拇指和手指的独立/灵巧的手写运动能力。在正常受试者中，字符尺寸越大，笔尖速度越快。因此，写一个字的时间是恒定的。从笔尖的加速度和抖动得出的参数显示，一些患者的笔迹移动不流畅。在一些感觉障碍患者中，书写字符的长度除以字符直径，显示出字符线条的摆动或冗余。无论笔迹还是描迹，左手的轨迹大小比右手大，大的比小的大。换句话说，用右手书写或描绘一个小的或规则大小的字符是后天习得的，也是熟练的。在没有感觉障碍的右利手偏瘫患者中，尽管右手书写和描绘的速度慢于左手，但这一比例与正常人相似。

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.