Postural Arm Drift Associated With Brain Lesions in Man

TESTS of the ability of a subject to maintain the raised arms in a designated position are frequently used in clinical practice. The test procedure varies with individual clinicians, but a common method requires the subject to maintain the arms in a bilaterally symmetrical, horizontal static posture without the aid of vision. Evaluation of the results of the test is then made by visual inspection of the degree of drift of the two arms from the designated posture. It is seldom appreciated, however, that very few experimental studies 1 have been made of the extent of postural arm drift in normal subjects; nor has any attempt been made to establish whether a subject's ability to maintain static postures is better with one arm than with the other. Further, there are no data available to permit comparative evaluation of the effects of localized brain lesions upon the ability to maintain