Motion templates with eye velocity gain fields for transformation of retinal to head centric flow.

Heading perception from the optic flow is more difficult during eye rotations than when the eye is stationary, because the centre of the retinal motion identifies the fixation direction rather than the direction of heading. Eye movement signals helps when motion parallax is absent. This paper distinguishes two different possibilities for interactions between eye movement and visual motion signals to perceive heading with a rotating eye. A pre-motion template transformation changes local retinal velocity into head centric velocity. These velocities then feed head centric motion templates. A post-motion template model combines oculomotor signals with retinal motion templates to arrive at head centric flow templates. The latter scheme involves eye velocity gain fields similar to the eye position gain fields as found in area 7a. We propose that the parietal cortex transforms retinal to head centric direction and retinal to head centric flow on the same principle.