Letters to Nature

Nature 410, 819-822 (12 April 2001) | doi:10.1038/35071081; Received 19 December 2000; Accepted 29 January 2001

The motor side of depth vision

Kai Schreiber1,2, J. Douglas Crawford2,3, Michael Fetter4 & Douglas Tweed1,2,3

  1. Departments of Physiology and Medicine, University of Toronto, 1 King's College Circle, M5S 1A8 Toronto, Canada
  2. Canadian Institutes of Health Research, Group for Action and Perception
  3. Centre for Vision Research, York University, 4700 Keele Street, M3J 1P3 Toronto, Canada
  4. Department of Neurology, University Hospital Tübingen, Hoppe-Seyler-Stras zlige 3, 72072 Tübingen, Germany

Correspondence to: Douglas Tweed1,2,3 Correspondence and requests for materials should be addressed to D.T. (e-mail: Email: douglas.tweed@utoronto.ca).

To achieve stereoscopic vision, the brain must search for corresponding image features on the two retinas1. As long as the eyes stay still, corresponding features are confined to narrow bands called epipolar lines2, 3. But when the eyes change position, the epipolar lines migrate on the retinas4, 5, 6. To find the matching features, the brain must either search different retinal bands depending on current eye position, or search retina-fixed zones that are large enough to cover all usual locations of the epipolar lines. Here we show, using a new type of stereogram in which the depth image vanishes at certain gaze elevations, that the search zones are retina-fixed. This being the case, motor control acquires a crucial function in depth vision: we show that the eyes twist about their lines of sight in a way that reduces the motion of the epipolar lines, allowing stereopsis to get by with smaller search zones and thereby lightening its computational load.