Abstract
Our brain uses visual flow patterns to derive important information about the rotation of the eye and head through space and the direction of self-motion. This information is processed in various regions along the visual hierarchy, some of which also receive non-visual signals. Several regions along the dorsal stream are selective for elementary motion, like area V3A, V6 and the middle temporal area (MT). Other areas in this path, like the medial superior temporal area (MST) and the ventral intra-parietal area (VIP), are particularly modulated by optic-flow patterns. They are closely involved in heading perception and are both modulated by vestibular and eye movement signals. Although most of these higher visual areas have been retinotopically mapped, their functional role is still poorly understood. Previously, we have identified a sub-region of pMST, to be modulated by visual flow signals corresponding to a rotation of the head. For this, we used stimuli that allowed dissociation between simulated head- and gaze rotation (see abstract: van den Berg et al.). Here, we show -using psychophysical techniques, high-resolution functional resonance imaging and wide-field visual stimuli- that: (1) perceived ego-rotation corresponds to the simulated head rotation rather than the gaze rotation. (2) like in pMST, regions within area V3A, V6 and pVIP show a specific modulation of the BOLD response to simulated head rotation. (3) these areas have a retinotopic organization. Our observations do not permit us to conclude in which reference frame the receptive fields collect the visual flow: retino-centric or head-centric? Possibly the multiple visual representations of head-rotation differ in this respect.
This work was Funded by NWO-ALW grant 818.02.006 (AvB).