Weight judgment in somesthesis after penetrating injury to the brain.

Abstract

Fifteen men with traumatic injury to the brain and consequent somatosensory deficit of the hand, 15 with traumatic injury to the brain without evidence of such deficit, 15 without brain injury but with injury to peripheral nerves of the arm; and 15 without brain injury but with injury to the peripheral nerves of the leg (controls) were stimulated simultaneously and successively on both supported palms with identical wts. (103.6 g.). Neither of the groups with peripheral nerve injury showed significant constant errors between the hands, but both brain-in jured groups demonstrated significant constant differences between the hands. These errors were in opposite directions: the group with brain injury and sensory deficit overestimated wts. on the affected hand as compared to the normal hand; the brain-injured group with no sensory deficit underestimated wts. on the hand contra-lateral to the brain injury as compared to the "normal" hand. A theory of the perception of intensities is proposed to account for the results.