Motor awareness and motor intention in anosognosia for hemiplegia

Abstract

In everyday life, a successful monitoring of behavior requires a continuous updating of the effect of motor acts. It is, therefore, crucial to know whether a programmed action has actually been performed. Some patients who, as consequence of right-brain damage, develop a paresis of the left side of the body, obstinately deny their motor deficit (motor denial or anosognosia), and when asked to move their paralysed limb they pretend having performed the action required by the examiner. Anosognosia has both clinical and theoretical implications. From a clinical point of view, anosognosia for hemiplegia can have a negative impact on motor rehabilitation. From a theoretical point of view, anosognosia can shed light on the neural structures that underlie conscious motor processes. We shall briefly review the clinical characteristics of anosognosia for hemiplegia, the false beliefs reported by the patients, the associations and dissociation with other neuropsychological symptoms and the anatomical correlation of the disorder. On the bases of anatomo-clinical data, it will be argued that anosognosia is due to the failure of a motor monitoring component that does not detect the mismatch between a desired action and the actual status of the sensorimotor system in face of an intact capacity of programming movements and forming sensorimotor predictions. This would imply that the brain activity leading to the construction of a conscious intention of action is normal. We shall present observational and electromyogram data strongly suggesting that motor intentional processes are still available in hemiplegic anosognosic patients.