Digitized analysis of handwriting and drawing movements in healthy subjects: methods, results and perspectives

The diagnosis of movement disorders and the distinction between their possible generation by drug-treatment or illness can be done more objectively by using digitized analyses of hand movements. The aim of this study was to define this method, that is to identify its reliability and the influence of several covariables upon measurements, in healthy subjects. Simple writing and drawing tests were administered, using a digitizing tablet, transmitting signals to a computer for processing. The kinematic parameters identified in this way provided objective, reliable and valid measures for the dynamics and the degree of automation of hand movements. Analysis of the data showed that younger subjects write faster and with a higher degree of automation than older subjects. Other moderating variables, such as verbal intelligence and customary motor activity in everyday life (motoric practice) could be identified, whereas personality and gender were found to have little influence. There were no significant differences between left-handers and right-handers in hand movements. The movement parameters had a high test retest stability. The results of this study in healthy subjects indicate that age, verbal intelligence and motor practice should be considered when evaluating the effects of drug-treatment or psychiatric illness upon hand-movement in patients.