Access through your institution Buy or subscribe Recently, people have become fascinated by autostereograms, in which a three-dimensional scene emerges when the eyes misconverge on an

apparently random array of dots. We now have stereoscopic virtual reality and stereoscopic ‘vision’ in robots. But what are the brain mechanisms that are involved in stereopsis (binocular

vision)2? An advance in our understanding of these mechanisms comes from results by Cumming and Parker3 and by Masson _et al_. 4, on pages 280and , respectively, of this issue. When we look

at a small object, the images of it fall on corresponding points in the two retinas. Neural signals from these corresponding points then converge on the same ‘binocular cell’ in the primary

idea is that optic-nerve fibres serving slightly different regions (receptive fields) in each of the two retinas converge onto the same binocular cell. Such a cell is a ‘disparity detector’,

because it responds best when the images in the two eyes have a disparity that matches the difference in the positions of the two receptive fields6. Different disparity detectors respond to

different signs and magnitudes of disparity. Zero-disparity detectors respond to objects in the plane of fixation, crossed-disparity detectors react to nearer objects, and

uncrossed-disparity detectors respond to more distant objects. This is a position-disparity mechanism. Disparities may also be detected by differences in the distribution of excitatory and

inhibitory regions within two receptive fields that do not differ in position. This is a phase-disparity mechanism. This is a preview of subscription content, access via your institution

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about institutional subscriptions * Read our FAQs * Contact customer support REFERENCES * Wheatstone, C. _Phil. Trans. R. Soc. Lond._ 128, 371–394 (1838). Google Scholar  * Howard, I. P.

& Rogers, B. J. _Binocular_ _Vision_ _and_ _Stereopsis_ (Oxford Univ. Press, New York, 1995). * Cumming, B. G. & Parker, A. J. _Nature_ 389, 280–283 (1997). Article  ADS  CAS  Google

Scholar  * Masson, G. S., Busettini, C. & Miles, F. A. _Nature_ 389, 283–286 (1997). Article  ADS  CAS  Google Scholar  * Hubel, D. H. & Wiesel, T. N. _J. Physiol. Lond._ 160,

106–154 (1962). Google Scholar  * Barlow, H. B., Blakemore, C. & Pettigrew, J. D. _J. Physiol. Lond._ 193, 327–342 (1967). Google Scholar  * Qian, N. _Vision Res._ 37, 1811–1827 (1997).

Google Scholar  * Ohzawa, I., DeAngelis, G. C. & Freeman, R. D. _J. Neurophysiol_. 77, 2879–2910 (1997). Google Scholar  * Jones, R. _Am. J. Optom. Physiol. Opt_. 57, 640–644 (1980).

Google Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * the Centre for Vision Research, York University, North York, M3J 1P3, Ontario, Canada Ian P. Howard Authors

* Ian P. Howard View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE

Howard, I. Seeing in reverse. _Nature_ 389, 235–237 (1997). https://doi.org/10.1038/38400 Download citation * Issue Date: 18 September 1997 * DOI: https://doi.org/10.1038/38400 SHARE THIS

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