Anosognosia for hemiplegia as a global deficit in motor awareness : evidence from the non-paralysed limb

Abstract

The current study adds to the growing empirical research into the mechanisms underlying unawareness of paralysis following stroke (anosognosia for hemiplegia or AHP) by investigating action awareness for the non-paralysed limb in a single AHP patient. Visual feedback representing patient GG's goal-directed reaching movements was either modified by a computer or left unperturbed. Unlike healthy and brain-damaged controls, GG was unable to detect computer-generated visual perturbations as large as 20°. GG also failed to report awareness of the large on-line corrective movements that he made when compensating (often unsuccessfully) for the visual perturbations. These results suggest that the motor comparators implicated in AHP are functioning, but not at optimum levels. Moreover, because the current findings reveal a deficit in awareness for reaches with the unimpaired limb, it is suggestive of common right hemisphere networks for motor awareness in both limbs and that AHP may be a global deficit in motor awareness as opposed to a specific lack of awareness for a particular motor deficit.