Global shape discrimination at reduced contrast in enucleated observers

Previous research has shown that observers with early unilateral enucleation have selectively better sensitivity to luminance contrast than monocular viewing controls [González et al., 2002; Vision Research 36 (1) (1996) 175; Vision Research 36 (1996) 3011; Vision Research 37 (17) (1997) 2465]. We asked whether unilateral enucleation specifically enhances all levels of luminance processing. Enucleated observers, as well as binocular and monocular viewing controls, detected global shape in radial frequency (RF) patterns [Vision Research 38 (1998) 2555] at low contrast. Control observers were tested in two monocular conditions in which the stimulus was presented to one eye, while the fellow eye: (1) viewed a luminance-matched grey field or (2) was covered by a dark eye patch. Sensitivity to low-contrast global shape was equivalent in enucleated observers and binocular controls. More importantly, enucleated observers showed superior performance to that of controls in either monocular condition. At low contrast, the dichoptic control group was more sensitive than controls wearing an eye patch, which suggests that dichoptic viewing is a superior method of testing when comparing monocular control performance to that of monocularly deprived populations. The previously reported enhanced sensitivity to luminance-defined form in early enucleated observers also occurs for low-contrast global shape discrimination.

[1]  R. Home,et al.  Binocular summation: A study of contrast sensitivity, visual acuity and recognition , 1978, Vision Research.

[2]  A. B. Nutt.  Binocular vision. , 1945, The British orthoptic journal.

[3]  D. Regan,et al.  Opponent model for line interval discrimination: Interval and vernier performance compared , 1987, Vision Research.

[4]  B. J. Winer,et al.  Statistical Principles in Experimental Design, 2nd Edition. , 1973 .

[5]  Robert Fox,et al.  The psychophysical inquiry into binocular summation , 1973 .

[6]  D. Hubel,et al.  Binocular interaction in striate cortex of kittens reared with artificial squint. , 1965, Journal of neurophysiology.

[7]  D Regan,et al.  Development of Motion-Defined Figure-Ground Segregation in Preschool and Older Children, Using a Letter-Identification Task , 1997, Optometry and vision science : official publication of the American Academy of Optometry.

[8]  Hugh R. Wilson,et al.  A deficit in strabismic amblyopia for global shape detection , 1999, Vision Research.

[9]  Ravi S. Menon,et al.  An fMRI study of the selective activation of human extrastriate form vision areas by radial and concentric gratings , 2000, Current Biology.

[10]  M. Pirenne,et al.  Binocular and Uniocular Threshold of Vision , 1943, Nature.

[11]  Albert O Edwards,et al.  Shape discrimination in age-related macular degeneration. , 2002, Investigative ophthalmology & visual science.

[12]  Alan Cowey,et al.  Contrast sensitivity in one-eyed subjects , 1996, Vision Research.

[13]  J. Steeves,et al.  Early unilateral enucleation disrupts motion processing , 2002, Vision Research.

[14]  P. Rakic,et al.  Development of visual centers in the primate brain depends on binocular competition before birth. , 1981, Science.

[15]  Ralph D. Freeman,et al.  Binocular summation in orientation discrimination depends on stimulus contrast and duration , 1994, Vision Research.

[16]  D M Levi,et al.  Binocular summation in vernier acuity. , 1991, Journal of the Optical Society of America. A, Optics and image science.

[17]  J. Steeves,et al.  Foveal and eccentric acuity in one-eyed observers , 2002, Behavioural Brain Research.

[18]  D. C. Essen,et al.  Neural responses to polar, hyperbolic, and Cartesian gratings in area V4 of the macaque monkey. , 1996, Journal of neurophysiology.

[19]  D. G. Green,et al.  Monocular versus Binocular Visual Acuity , 1965, Nature.

[20]  Gordon E. Legge,et al.  Binocular contrast summation—I. Detection and discrimination , 1984, Vision Research.

[21]  J. Steeves,et al.  Contrast Letter Thresholds in the Non-affected Eye of Strabismic and Unilateral Eye Enucleated Subjects , 1996, Vision Research.

[22]  Visual loss during interocular suppression in normal and strabismic subjects , 1994, Vision Research.

[23]  L. Kaufman,et al.  Handbook of perception and human performance , 1986 .

[24]  H. Wilson,et al.  Concentric orientation summation in human form vision , 1997, Vision Research.

[25]  J. Horton,et al.  Effect of early monocular enucleation upon ocular dominance columns and cytochrome oxidase activity in monkey and human visual cortex , 1998, Visual Neuroscience.

[26]  Christian Wehrhahn,et al.  Contrast dependency of foveal spatial functions: orientation, vernier, separation, blur and displacement discrimination and the tilt and Poggendorff illusions , 1999, Vision Research.

[27]  H. Ono,et al.  Vernier acuity in monocular and binocular children , 1992 .

[28]  M W HOROWITZ,et al.  An analysis of the superiority of binocular over monocular visual acuity. , 1949, Journal of experimental psychology.

[29]  Ravi S. Menon,et al.  BOLD fMRI response of early visual areas to perceived contrast in human amblyopia. , 2000, Journal of neurophysiology.

[30]  B. J. Winer.  Statistical Principles in Experimental Design , 1992 .