ANOSOGNOSIA FOR HEMIPLEGIA - AN ELECTROPHYSIOLOGIC INVESTIGATION OF THE FEEDFORWARD HYPOTHESIS

The cause of anosognosia for hemiplegia (AHP) remains unclear. Weaknes s is detected when there is a mismatch between the expectancy of movem ent and the sensory perception of movement. The feed-forward hypothesi s of AHP posits that there is a failure of detection because there is a loss of motor intention and expectancy of movement. We tested motor intention by measuring the activation of proximal muscles (pectoralis majoris) while subjects squeezed a dynamometer with each hand. We test ed a group of normal controls, a group of patients with hemiparesis, a patient with neglect, a patient with resolved AHP, and a patient with persistent AHP. The patient with AHP did not contract either of his p ectoralis muscles when asked to squeeze with his contralesional, paret ic hand, yet he contracted both of them when squeezing the dynamometer with his ipsilesional hand. Normal controls, hemiparetic controls, an d the patient with hemispatial neglect contracted both pectorales when asked to squeeze with each hand. The pattern of activation seen in th e patients with persistent AHP and resolved AHP demonstrates a loss of motor intention and lends support to the feed-forward hypothesis of A HP.