G. Galati et al., The neural basis of egocentric and allocentric coding of space in humans: a functional magnetic resonance study, EXP BRAIN R, 133(2), 2000, pp. 156-164
The spatial location of an object can be represented in the brain with resp
ect to different classes of reference frames, either relative to or indepen
dent of the subject's position. We used functional magnetic resonance imagi
ng to identify regions of the healthy human brain subserving mainly egocent
ric or allocentric (object-based) coordinates by asking subjects to judge t
he location of a visual stimulus with respect to either their body or an ob
ject. A color-judgement task, matched for stimuli, difficulty, motor and oc
ulomotor responses, was used as a control. We identified a bilateral, thoug
h mainly right-hemisphere based, fronto-parietal network involved in egocen
tric processing. A subset of these regions, including a much less extensive
unilateral, right fronto-parietal network, was found to be active during o
bject-based processing. The right-hemisphere lateralization and the partial
superposition of the egocentric and the object-based networks is discussed
in the light of neuropsychological findings in brain-damaged patients with
unilateral spatial neglect and of neurophysiological studies in the monkey
.