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Abstract:
Spatial localization tasks can be differentiated both by the
goal of the observer and by the spatial frames of reference used.
The goal may be an immediate visually guided action towards an
object in space or a longer-lasting spatial representation.
Location may be represented relative to the observer's position
(egocentric) or to another object's position (object-relative). We
investigated distinctions in the neural mechanisms subserving
egocentric and object-relative spatial processing in a non-motoric
task using functional magnetic resonance imaging (fMRI).
Participants were presented with the same display for two spatial
judgment tasks and a control task. The display consisted of a
picture of a rotated car with a star on one of its four sides.
Participants performed an egocentric task, "where is the star
relative to you?", "an object-relative task, "where is the star
relative to the car?" or a control task, "is the star present or
absent?". The results indicated an extensive bilateral superior
parietal-frontal network of activation associated with the
egocentric task compared to the object-relative task. Both tasks
shared similar areas of parietal activation. These findings suggest
different neural mechanisms for coding the positions of objects in
space based on the reference frame used, supporting recent animal
neurophysiology and human neuropsychology research.
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