Anosognosia: examining the disconnection hypothesis.

OBJECTIVE To test the hypothesis that anosognosia for hemiparesis results from intrahemispheric disconnection. METHODS Using right carotid barbiturate injection as a model for anosognosia for hemiparesis, systematic attempts were made to modify deficit awareness by providing the left hemisphere with explicit information regarding left upper extremity function. RESULTS Experimental interventions failed to modify deficit awareness in 19 of 32 patients. In those patients who discovered their weakness, attempted movement of the weak limb seems more important than explicit observation of the extremity by the left hemisphere. CONCLUSIONS The results fail to support Geschwind's disconnection hypothesis for anosognosia for hemiparesis.