By systematically manipulating head position relative to the body
and eye position relative to the head, previous studies have shown
that vestibular tuning curves of neurons in the ventral intraparietal
(VIP) area remain invariant when expressed in body-/world-centered
coordinates. However, body orientation relative to the world was not
manipulated; thus, an egocentric, body-centered representation could
not be distinguished from an allocentric, world-centered reference
frame. We manipulated the orientation of the body relative to the
world such that we could distinguish whether vestibular heading
signals in VIP are organized in body- or world-centered reference
frames. We found a hybrid representation, depending on gaze
direction. When gaze remained fixed relative to the body, the
vestibular heading tuning of VIP neurons shifted systematically with
body orientation, indicating an egocentric, body-centered reference
frame. In contrast, when gaze remained fixed relative to the world,
this representation changed to be intermediate between body- and
world-centered. We conclude that the neural representation of
heading in posterior parietal cortex is flexible, depending on gaze
and possibly attentional demands.