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An unexpected specialization for horizontal disparity in primate primary visual cortex


The horizontal separation of the eyes means that objects nearer or farther than the fixation point project to different locations on the two retinae, differing principally in their horizontal coordinates (horizontal binocular disparity). Disparity-selective neurons have generally been studied with disparities applied in only one direction1 (often horizontal), which cannot determine whether the encoding is specialized for processing disparities along the horizontal axis. It is therefore unclear if disparity selectivity represents a specialization for naturally occurring disparities. I used random dot stereograms to study disparity-selective neurons from the primary visual cortex (V1) of awake fixating monkeys. Many combinations of vertical and horizontal disparity were used, characterizing the surface of responses as a function of two-dimensional disparity. Here I report that the response surface usually showed elongation along the horizontal disparity axis, despite the isotropic stimulus. Thus these neurons modulated their firing rate over a wider range of horizontal disparity than vertical disparity. This demonstrates that disparity-selective cells are specialized for processing horizontal disparity, and that existing models2,3 of disparity selectivity require substantial revision.

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Figure 1: Responses of four neurons to combinations of vertical and horizontal disparities.
Figure 2: Relationship between disparity tuning and receptive-field orientation, for simple models1.
Figure 3: Orientation of the disparity tuned response as a function of monocular orientation preference (dominant eye).
Figure 4: For each neuron, the preferred disparity identifies the disparity combination yielding the strongest response.
Figure 5: In order to select the disparity combinations used, a wide range of disparities were first explored along each of two axes (solid symbols).


  1. Cumming, B. G. & DeAngelis, G. C. The physiology of stereopsis. Annu. Rev. Neurosci. 24, 203–238 (2001)

    CAS  Article  Google Scholar 

  2. Ohzawa, I. Mechanisms of stereoscopic vision: the disparity energy model. Curr. Opin. Biol. 8, 509–515 (1998)

    CAS  Google Scholar 

  3. Ohzawa, I., DeAngelis, G. C. & Freeman, R. D. Stereoscopic depth discrimination in the visual cortex: Neurons ideally suited as disparity detectors. Science 249, 1037–1041 (1990)

    ADS  CAS  Article  Google Scholar 

  4. Mayhew, J. & Longuet-Higgins, H. C. A computational model of binocular depth perception. Nature 297, 376–378 (1982)

    ADS  CAS  Article  Google Scholar 

  5. Howard, I. P. & Rogers, B. J. Binocular Vision and Stereopsis (Oxford Univ. Press, Oxford, 1995)

    Google Scholar 

  6. Anzai, A., Ohzawa, I. & Freeman, R. D. Neural mechanisms for processing binocular information II. Complex cells. J. Neurophysiol. 82, 909–924 (1999)

    CAS  Article  Google Scholar 

  7. Barlow, H. B., Blakemore, C. & Pettigrew, J. D. The neural mechanisms of binocular depth discrimination. J. Physiol. (Lond.) 193, 327–342 (1967)

    CAS  Article  Google Scholar 

  8. Joshua, D. E. & Bishop, P. O. Binocular single vision and depth discrimination: Receptive field disparities for central and peripheral vision and binocular interaction of peripheral single units in cat striate cortex. Exp. Brain Res. 10, 389–416 (1970)

    CAS  Article  Google Scholar 

  9. Heydt, R. v. d., Adorjani, C., Anny, P. H. & Baumgartner, G. Disparity sensitivity and receptive field incongruity of units in the cat striate cortex. Exp. Brain Res. 31, 523–545 (1978)

    Article  Google Scholar 

  10. Maunsell, J. H. R. & van Essen, D. C. Functional properties of neurons in middle temporal visual area of the macaque monkey. II. Binocular interactions and sensitivity to binocular disparity. J. Neurophysiol. 49, 1148–1166 (1983)

    CAS  Article  Google Scholar 

  11. Nieder, A. & Wagner, H. Encoding of both vertical and horizontal disparity in random-dot stereograms by Wulst neurons of awake barn owls. Vis. Neurosci. 18, 541–547 (2001)

    CAS  Article  Google Scholar 

  12. DeAngelis, G. C., Ohzawa, I. & Freeman, R. D. Depth is encoded in the visual cortex by a specialized receptive field structure. Nature 352, 156–159 (1991)

    ADS  CAS  Article  Google Scholar 

  13. Hubel, D. H. & Wiesel, T. N. Receptive fields and functional architecture of monkey striate cortex. J. Physiol. (Lond.) 195, 215–243 (1968)

    CAS  Article  Google Scholar 

  14. Cumming, B. G. & Parker, A. J. Responses of primary visual cortical neurons to binocular disparity without depth perception. Nature 389, 280–283 (1997)

    ADS  CAS  Article  Google Scholar 

  15. Ohzawa, I., DeAngelis, G. C. & Freeman, R. D. Encoding of binocular disparity by complex cells in the cat's visual cortex. J. Neurophysiol. 77, 2879–2909 (1997)

    CAS  Article  Google Scholar 

  16. Livingstone, M. S. & Tsao, D. Y. Receptive fields of disparity-selective neurons in macaque striate cortex. Nature Neurosci. 2, 825–832 (1999)

    CAS  Article  Google Scholar 

  17. Cumming, B. G. & Parker, A. J. Binocular neurons in V1 of awake monkeys are selective for absolute, not relative, disparity. J. Neurosci. 19, 5602–5618 (1999)

    CAS  Article  Google Scholar 

  18. Cumming, B. G. & Parker, A. J. Local disparity not perceived depth is signalled by binocular neurons in cortical area V1 of the macaque. J. Neurosci. 20, 4758–4767 (2000)

    CAS  Article  Google Scholar 

  19. Prince, S. J. D., Pointon, A. D., Cumming, B. G. & Parker, A. J. The precision of single neuron responses in cortical area V1 during stereoscopic depth judgements. J. Neurosci. 20, 3387–3400 (2000)

    CAS  Article  Google Scholar 

  20. Prince, S. J. D., Cumming, B. G. & Parker, A. J. Range and mechanism of horizontal disparity encoding in macaque V1. J. Neurophysiol. 87, 209–221 (2002)

    CAS  Article  Google Scholar 

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Cumming, B. An unexpected specialization for horizontal disparity in primate primary visual cortex. Nature 418, 633–636 (2002).

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