SENSITIVITY TO FULL-FIELD VISUAL MOVEMENT COMPATIBLE WITH HEAD ROTATION - VARIATIONS WITH EYE-IN-HEAD POSITION

Variations in velocity detection thresholds for full-field visual rota tion about various axes are compatible with a simple channel-based sys tem for coding the axis and velocity of the rotation (Harris & Lott, 1 995). The present paper looks at the frame of reference for this syste m. The head-centered, craniotopic reference system and the retinal-bas ed, retinotopic reference systems were separated by using eccentric ey e positions. We measured the threshold for detecting full-field visual rotation about a selection of axes in the sagittal plane with the eye s held either 221/2, degs up, straight ahead or 221/2 degs down in the head. The characteristic features of the variation in detection thres holds did not stay stable in craniotopic coordinates but moved with th e eyes and were constant in retinotopic coordinates. This suggests tha t the coding of head rotation by the visual system is in retinotopic c oordinates.