Effects of age on distally and proximally generated drawing movements: a kinematic analysis of school children and adults

The effects of age on basic fine motor functions were assessed using a kine matic analysis of simple repetitive drawing movements in a sample of 53 rig ht-handed children aged 7 to 14 years 11 months and 16 adults aged 27 to 54 years with no detectable abnormality with neurological examination. Lines, circles, and half-circles were drawn at a self-chosen and maximum velocity with a pressure-sensitive pen on a computer graphics tablet. Patterns gene rated by finger, wrist, and arm movements, and those generated by combined finger-wrist movements with and without a change in the drawing direction w ere analysed. The frequencies of all movement patterns increased until adul thood: 0.1 Hz per year for half-circles, 0.15 to 0.2 Hz per year for circle s and lines generated by arm and wrist movements. The greatest increase (0. 35 Hz per year) was observed for lines produced by finger movements. Differ ences in movement frequencies between finger versus wrist or arm movements when drawing lines decreased from about 3 Hz in 7- to 8-year-olds to 0.5 to 1 Hz in adolescents. In adults the difference between maximum finger, wris t, and arm movement frequencies decreased to almost zero. In contrast, the differences in movement patterns with and without change in direction remai ned stable until adulthood. Based on these results it is hypothesized that the differential effects of finger and more proximally generated movements on age reflect maturation of distinct neuronal sites of the corticostriatal -cerebellar circuit rather than acquisition of motor skills or myelinizatio n of corticostriatal pathways.