Age-related differences in sensorimotor representation of space in drawing by hand

To address the question of the space sensorimotor representation during hand-writing and its modifications with aging. We have chosen to study the drawing ellipses without visual guidance. We hypothesized that the decreased manual dexterity associated with aging could be attributed, in part, to the modification of space representation for action.

Young and elderly subjects drew ellipses with the tip of the index in the three anatomical planes: sagittal, frontal and horizontal. The 3D movements were recorded by a portable Video Recorder (3DVR) adapted to a clinical examination room with a natural light source.

All subjects showed large disparities in errors in the various planes. Errors were maximal in the horizontal plane. These findings confirm the assumption of an anisotropic action-related representation of space when the movement is performed in a peripersonal frame of reference. Compared with young subjects, the results demonstrate that aging is associated with an important decreased ability to draw precisely ellipses in the three body-defined reference frames.

Space representation is altered with aging. This finding supports the idea that the central nervous system is apparently able to maintain hand-drawing performance at a good level independently of the anisotropic character of the egocentric space.

These findings may contribute to introducing new functional clinical tests and open new perspectives for future investigations on the age-related changes in hand function.