Phenomenology and neural correlates of implicit and emergent motor awareness in patients with anosognosia for hemiplegia

Anosognosia for hemiplegia (AH) is characterized by a lack of awareness of motor disorders and appearsassociated with fronto-temporal-parietal damage. Neuropsychological evidence indicates that behavioralindices of residual forms of motor awareness may co-exist with explicit denial of impairment. Herewe explore whether the attempt by AH patients to perform an action may disclose residual forms ofmotor awareness and whether such forms are underpinned by different neural structures. Twelve hemiplegicpatients affected by AH were tested in tasks assessing: (i) implicit awareness (IA), indexed bydiscrepancies between verbal reports and actual motor behavior; (ii) emergent awareness (EA), indexedby increased verbal awareness induced by the attempt to perform actions. IA and EA were found in fiveand three patients, respectively. Lesion analysis indicates that while the lack of IA is associated with damageto subcortical white matter anterior to the basal ganglia, lack of EA is linked to damage to corticalregions including insulo-frontal, temporal and parietal structures. Our results indicate that deficits inexplicit and implicit awareness are associated with lesions involving different cortico–subcortical structures.Moreover, the results show that the attempt to perform an action may ameliorate body awarenessdeficits and have implications for rehabilitation.