Translocation of the embodied self without visuospatial neglect

This is the case report of RB,a 68-year-old retired woman who,following an extensive right sided ischaemic stroke,showed hemiplegia,anosognosia and allochiria,but no somato-sensory deficits and no visuospatial neglect. A high resolution 3D MRI structural scan of her brain was acquired to define the structural damage in detail. Morphometric analyses of grey and white matter data revealed a large lesion which involved most of her right parietal,temporal,and mesial frontal cortex,with partial sparing of the right dorsolateral prefrontal cortex and part of the posterior corpus callosum. Detailed examination showed that RB attributed sensory stimuli,both on the left and on the right,to the opposite side of her body. This mirror reversed representation of her body caused misattribution of items even in the absence of stimulation,as for instance when the patient spontaneously reported pain in her right knee while pointing to her left knee. RB's neuropsychological profile showed normal or borderline performance on most cognitive tasks. Language comprehension was intact and she could tell left from right without difficulty in all instances except for those referable to her soma. To our knowledge this is the first description of severe allochiria for body representation in the absence of neglect. The evidence from this case supports the developing concept that the body representation is not simply a systematic registration of proprioceptive inputs,but that the brain has a more sophisticated high level representation of one's body map which is updated on the basis of multimodal information.