Anosognosia for plegia : specificity, extension, partiality and disunity of bodily unawareness
This study of anosognosia for hemiplegia investigated: whether it is homogeneous; specificity to plegia of unawareness; extension to different kinds of and objects of awareness regarding plegia; partiality of unawareness. Sixty-four hemiplegic stroke patients were assessed with control subjects on (a) motor and somatosensory function, immediately followed by participants' evaluations of performance; (b) conventional structured interview questions addressing awareness of various capacities; (c) Neglect, Mental Flexibility, General Mental State, Verbal Fluency, Short-Term Memory; (d) pre- and post- performance estimates of ability on the last two; (e) estimates of current ability on bilateral and unilateral tasks, addressed by questions in 1st- and 3rd-person forms, explanations of how overestimated tasks would be accomplished, attempts at 3 bimanual tasks and post-attempt estimates of ability on these. Anosognosia for plegia was mostly associated with right-brain damage. No single factor or combination accounted for all patients. Double dissociations indicated that anosognosia can be specific to plegia; and patients do not generally overestimate other abilities. Although unawareness of paralysis and of its consequences appear linked, the latter is more widespread and persistent. Double dissociation showed that concurrent unawareness of movement failures is a separate deficit from these. There was differential awareness of different aspects of plegia. Further, some patients who overestimated current bilateral task ability when asked in 1st-person form did not overestimate when asked how well the examiner, if he was in their current condition, could do each task. This suggests split awareness of a single aspect of plegia. Patients anosognosic on conventional questioning showed two distinctions. (1) Some were unaware of movement failures when they occurred; others were aware but quickly forgot such failures and seem unable to update long-term body knowledge. (2) Some patients' explanations of bimanual task performance reflect unawareness of hemiplegia; others' explanations were bizarre and imply some awareness. The latter group's deficit appears to be nonspecific and linked to right-hemisphere predominance of anosognosia, an account of which is offered. Anosognosia for hemiplegia is not a unitary phenomenon: several factors underlie deficits in bodily awareness.