Anosognosia for apraxia: experimental evidence for defective awareness of one's own bucco-facial gestures.

Anosognosia is a multifaceted, neuro-psychiatric syndrome characterized by defective awareness of a variety of perceptuo-motor, cognitive or emotional deficits. The syndrome is also characterized by modularity, i.e., deficits of awareness in one domain (e.g., spatial perception) co-existing with spared functions in another domain (e.g., memory). Anosognosia has mainly been reported after right hemisphere lesions. It is however somewhat surprising that no studies have thus far specifically explored the possibility that lack of awareness involves apraxia, i.e., a deficit in the ability to perform gestures caused by an impaired higher-order motor control and not by low-level motor deficits, sensory loss, or failure to comprehend simple commands. We explored this issue by testing fifteen patients with vascular lesions who were assigned to one of three groups depending on their neuropsychological profile and brain lesion. The patients were asked to execute various actions involving the upper limb or bucco-facial body parts. In addition they were also asked to judge the accuracy of these actions, either performed by them or by other individuals. The judgment of the patients was compared to that of two external observers. Results show that our bucco-facial apraxic patients manifest a specific deficit in detecting their own gestural errors. Moreover they were less aware of their defective performance in bucco-facial as compared to limb actions. Our results hint at the existence of a new form of anosognosia specifically involving apraxic deficits.