Neuropsychological studies suggest that patients with left parietal
lesions may show impaired localization of parts of either their own
or the examiner’s body, despite preserved ability to identify isolated
body parts. This deficit, called autotopagnosia, may result from
damage to the Body Structural Description (BSD), a representation
which codes spatial relationships among body parts. We used
functional magnetic resonance imaging to identify the neural
mechanisms underlying the BSD. Two human body or building parts
(factor: STIMULI) were shown to participants who either identified
them or evaluated their distance (factor: TASK). The analysis of the
interaction between STIMULI and TASK, which isolates the neural
mechanism underlying BSD, revealed an activation of left posterior
intraparietal sulcus (IPS) when the distance between body parts
was evaluated. The results show that the left IPS processes
specifically the information about spatial relationships among body
parts and thereby suggest that damage to this area may underlie
autotopagnosia.
