Disturbances of motor reaching behavior. Clinical note.

Disturbance of motor reaching behavior was found in a patient submitted to a partial lobectomy including the posterior regions of the parietal cortex. The altered function could be objectivated by means of a battery of tests designed to detect visuo-spatial appreciation following which the subject has to point out to the center of figures with different configurations. Likewise, the damaged motor function could also be detected when the patient intended to reproduce, by copying, models of a figure as well as of straight lines of different lengths. Difficulties to reach -on first attempt- the proper point on the sheet with the point of the pencil, brought the performance of these tests to a high degree of inexactness and showed clearly the inaccuracy in production of voluntary motor responses within concretely definable visuo-spatial limits. These findings can be considered to be similar to those described in monkeys after removal of parieto-occipital cortex. It might be that a lesion in this part of the brain disrupt the high level of elaboration of different kind of stimuli (tactile, proprioceptive, visual, etc.) indispensable to attain normal reaching motor functions.