Mentalizing the body
Brain. 2016-01-24; 139(3): 971-985
DOI: 10.1093/brain/awv390
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Following right-hemisphere damage, a specific disorder of motor awareness can
occur called anosognosia for hemiplegia, i.e. the denial of motor deficits
contralateral to a brain lesion. The study of anosognosia can offer unique
insights into the neurocognitive basis of awareness. Typically, however,
awareness is assessed as a first person judgement and the ability of patients to
think about their bodies in more ‘objective’ (third person) terms is not directly
assessed. This may be important as right-hemisphere spatial abilities may
underlie our ability to take third person perspectives. This possibility was
assessed for the first time in the present study. We investigated third person
perspective taking using both visuospatial and verbal tasks in right-hemisphere
stroke patients with anosognosia (n = 15) and without anosognosia (n = 15), as
well as neurologically healthy control subjects (n = 15). The anosognosic group
performed worse than both control groups when having to perform the tasks from a
third versus a first person perspective. Individual analysis further revealed a
classical dissociation between most anosognosic patients and control subjects in
mental (but not visuospatial) third person perspective taking abilities. Finally,
the severity of unawareness in anosognosia patients was correlated to greater
impairments in such third person, mental perspective taking abilities (but not
visuospatial perspective taking). In voxel-based lesion mapping we also
identified the lesion sites linked with such deficits, including some brain areas
previously associated with inhibition, perspective taking and mentalizing, such
as the inferior and middle frontal gyri, as well as the supramarginal and
superior temporal gyri. These results suggest that neurocognitive deficits in
mental perspective taking may contribute to anosognosia and provide novel
insights regarding the relation between self-awareness and social cognition.
© The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain.