Awareness of the functioning of one's own limbs mediated by the insular cortex?

Normally, we are aware of the current functions of our arms and legs. However, this self-evident status may change dramatically after brain damage. Some patients with "anosognosia" typically are convinced that their limbs function normally, although they have obvious motor defects after stroke. Such patients may experience their own paretic limbs as strange or as not belonging to them and may even attribute ownership to another person and try to push their paralyzed limb out of bed. These odd beliefs have been attributed to disturbances somewhere in the right hemisphere. Here, we use lesion mapping in 27 stroke patients to show that the right posterior insula is commonly damaged in patients with anosognosia for hemiplegia/hemiparesis but is significantly less involved in hemiplegic/hemiparetic patients without anosognosia. The function of the posterior insular cortex has been controversially discussed. Recent neuroimaging results in healthy subjects revealed specific involvement of this area in the subject's feeling of being versus not being involved in a movement. Our finding corresponds with this observation and suggests that the insular cortex is integral to self-awareness and to one's beliefs about the functioning of body parts.