Abstract:
Anosognosia for hemiplegia, an individual’s unawareness of his/her paralysed limbs, can occur after stroke. A recent theory postulated that anosognosia for hemiplegia is a result of failures in reality monitoring abilities. One example of faulty reality monitoring is seen in confabulation. Failure in accurate representation of mental states may also cause deficits in reality monitoring processes. This study aimed to assess two behaviours reflecting reality monitoring (presence of confabulations, theory of mind abilities) in individuals with, and without anosognosia following a right-hemisphere stroke inducing left hemiplegia. Thirtythree stroke participants, and 22 non-brain damaged hospitalised control participants were included in the study. Anosognosia was associated with larger lesions involving both cortical and subcortical areas. The presence of neglect was also associated with significantly larger lesions than stroke participants without neglect. All participants were tested on a Provoked Confabulation task (PCT) and Theory of Mind (ToM) task. The anosognosia group produced more confabulatory responses on the PCT but 5/6 individuals had concurrent neglect. Further analyses revealed that presence of neglect, rather than anosognosia, was associated with elevated confabulatory responses. On the ToM task, contrary to predictions the nonanosognosia group and not the anosognosia group, demonstrated a selective deficit in ToM abilities. Stroke participants without neglect or anosognosia demonstrated a clear pattern of differential impairment on ToM cartoons. Individuals with neglect had difficulty on ToM cartoons, but also had difficulty on some inference questions not involving theory of mind abilities, thus limiting conclusions. In summary, no evidence was found to indicate that specific deficits in reality monitoring as measured by confabulation or impaired theory of mind abilities could account for the syndrome causing anosognosia for hemiplegia in this sample. Deficits in theory of mind in this study were apparent following right hemisphere stroke inducing hemiplegia when not accompanied by neglect or anosognosia. Our findings support the view that a strong association exists between neglect and anosognosia. Unexpectedly, presence of neglect had a greater influence in affecting reality monitoring abilities, with neglect participants showing higher levels of confabulation and selective impairment in ToM cartoons.