Abstract

The sustained spatial-frequency-tuned (SF-tuned) mechanisms of nonoriented units were examined by means of orthogonal masking for the Red–Green (R–G) color channel, and those of oriented units by oblique masking for the achromatic channel but not for the color channels. An oblique-masking technique minimizes the artifacts that are due to spatial phase effects, local cues, spatial beats, spatial probability summation, and changing criteria. Therefore the spatial characteristics of the R–G color channel are now investigated by an oblique-masking technique and linked with my paper on orthogonal masking [J. Opt. Soc. Am. A 15, 1 (1998)]. The R–G channel was defined by the minimum-flicker and hue-cancellation techniques. A color monitor system was used to generate spatially localized (D6) vertical color test patterns [0.063–8 cycles per degree (cpd)] and sinusoidal oblique color masks (0.031–16 cpd, 1.2–60% contrasts). Color contrast sensitivity functions (CSFs), threshold elevation (TE) versus mask SF (TvSF) curves, and TE versus mask contrast (TvC) curves were measured by the method of constant stimuli with a two-interval forced-choice technique by using Powell’s achromatizing lens under sustained (Gaussian, 2-s-duration) conditions. Results show the following: (1) The color CSF is a low-pass function of SF with average half-height SF of 0.7 cpd and cutoff SF of 14 cpd with the use of a color-detection criterion. (2) TvSF curves are broadly bandpass and fall into five groups, peaking at approximately 0.13, 0.5, 2, 4, and 8 cpd. The root-mean-square cone-color CSF is 3.8–5.4 times the stimulus-color CSF.(3) A “crowding effect” similar to that of the TvSF curves of the achromatic channel was also found, but the TvSF curves of the R–G channel are not sharply peaked, similar to the result for orthogonal masking. Data analysis led to the following conclusions: (1) A simple multiple-mechanism model yields one low-pass color mechanism (with average half-height SF of 0.54 cpd) and five bandpass SF-tuned color mechanisms; these six mechanisms are necessary to explain the CSF, TvSF, and TvC data simultaneously. (2) The bandpass mechanisms peaked at approximately 0.13, 0.5, 2, 4, and 8 cpd with average full bandwidths at half-heights of 3.6, 3.2, 2.1, 1.2, and 1.3 octaves, respectively.(3) Since oblique-masking color mechanisms (unlike achromatic oriented mechanisms) have broad orientation tuning under sustained conditions and there is a significant orthogonal masking, the oblique-masking color mechanisms may have contributions from both oriented and nonoriented units. (4) The high degree of similarity between the SF-tuned filters of mechanisms derived from oblique- and orthogonal-masking data suggests that most of the chromatic SF tuning is already accomplished by nonoriented units.(5) The quality of the fit to oblique- and orthogonal-masking data combined dropped enough to reject the hypothesis that the former taps the performance of only the same nonoriented mechanisms as those by the latter. Adding gain parameters that reduce the TEs for orthogonal masking gave a better fit, suggesting that orientation gains are one of the factors involved in the transformation of information from nonoriented to oriented mechanisms. However, the fit was still worse than that for oblique-masking-alone or orthogonal-masking-alone data, suggesting that more factors may be involved. (6) Since primate parvo lateral geniculate nucleus (pLGN) units behave in a fairly linear manner, the color contrast nonlinearity (which follows the linear filter) of a mechanism may be post-pLGN.

© 2002 Optical Society of America

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References

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2000 (2)

R. L. P. Vimal, “Spatial color contrast matching: broad-bandpass functions and the flattening effect,” Vision Res. 40, 3231–3243 (2000).
[CrossRef] [PubMed]

C. Chen, J. M. Foley, D. H. Brainard, “Detection of chromoluminance patterns on chromoluminance pedestals. II: model,” Vision Res. 40, 789–803 (2000).
[CrossRef]

1998 (2)

1997 (2)

R. L. P. Vimal, “Orientation tuning of the spatial frequency tuned mechanisms of the Red–Green channel,” J. Opt. Soc. Am. A 14, 2622–2632 (1997).
[CrossRef]

K. T. Mullen, S. J. Cropper, M. A. Losada, “Absence of linear subthreshold summation between Red–Green and luminance mechanisms over a wide range of spatio-temporal conditions,” Vision Res. 37, 1157–1165 (1997).
[CrossRef] [PubMed]

1995 (1)

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

1994 (4)

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

K. T. Mullen, M. A. Losada, “Evidence for separate pathways for color and luminance detection mechanisms,” J. Opt. Soc. Am. A 11, 3136–3151 (1994).
[CrossRef]

R. Pandey, R. L. P. Vimal, “Spatial frequency tuned mechanisms of the Red–Green channel estimated by oblique masking,” Soc. Neurosci. Abstr. 20 (Part 2), 1580 (1994).

M. A. Losada, K. T. Mullen, “The spatial tuning of chromatic mechanisms identified by simultaneous masking,” Vision Res. 34, 331–334 (1994).
[CrossRef] [PubMed]

1993 (4)

R. Pandey, R. L. P. Vimal, “Threshold elevation curves for the Red–Green channel estimated by oblique masking,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 751 (1993).

G. R. Cole, T. Hine, W. McIlhagga, “Detection mechanisms in L-, M- and S-cone contrast space,” J. Opt. Soc. Am. A 10, 38–51 (1993).
[CrossRef] [PubMed]

J. Ross, H. R. Speed, M. J. Morgan, “The effects of adaptation and masking on incremental threshold for contrast,” Vision Res. 33, 2051–2056 (1993).
[CrossRef] [PubMed]

C. W. Tyler, L. Barghout, L. L. Kontsevich, “Surprises in analyzing the mechanisms underlying threshold elevation functions,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 819 (1993).

1992 (1)

R. L. P. Vimal, R. Pandey, “In search of a spatial low-pass mechanism for sustained chromatic contrast sensitivity function by masking,” Invest. Ophthalmol. Visual Sci. Suppl. 33, 704 (1992).

1991 (1)

J. Ross, H. R. Speed, “Contrast adaptation and contrast masking in human vision,” Proc. R. Soc. London Ser. B 246, 61–69 (1991).
[CrossRef]

1990 (4)

P. Flanagan, P. Cavanagh, O. E. Favreau, “Independent orientation-selective mechanisms for the cardinal direction of color space,” Vision Res. 30, 769–778 (1990).
[CrossRef]

B. B. Lee, J. Pokorny, V. C. Smith, P. R. Martin, A. Valberg, “Luminance and chromatic modulation sensitivity of macaque ganglion cells and human observers,” J. Opt. Soc. Am. A 7, 2223–2236 (1990).
[CrossRef] [PubMed]

P. Lennie, J. Krauskopf, G. Sclar, “Chromatic mechanisms in striate cortex of macaque,” J. Neurosci. 10, 649–669 (1990).
[PubMed]

M. A. Webster, K. K. De Valois, K. Switkes, “Orientation and spatial-frequency discrimination for luminance and chromatic gratings,” J. Opt. Soc. Am. A 7, 1034–1049 (1990).
[CrossRef] [PubMed]

1989 (4)

R. L. P. Vimal, R. Pandey, “Spatial frequency discrimination for inphase and counter-phase red–green stimuli: effect of apparent motion,” Soc. Neurosci. Abstr. 15, 625 (1989).

R. L. P. Vimal, J. M. Pokorny, V. C. Smith, S. K. Shevell, “Foveal cone thresholds,” Vision Res. 29, 61–78 (1989).
[CrossRef] [PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque,” J. Neurosci. 9, 1433–1442 (1989).
[PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Sensitivity of macaque retinal ganglion cells to chromatic and luminance flicker,” J. Physiol. (London) 414, 223–244 (1989).

1988 (4)

E. Switkes, A. Bradley, K. K. De Valois, “Contrast dependence and mechanisms of masking interactions among chromatic and luminance gratings,” J. Opt. Soc. Am. A 5, 1149–1162 (1988).
[CrossRef] [PubMed]

A. Bradley, E. Switkes, K. De Valois, “Orientation and spatial frequency selectivity of adaptation to color and luminance gratings,” Vision Res. 28, 841–856 (1988).
[CrossRef] [PubMed]

M. W. Greenlee, S. Magnussen, “Interaction among spatial frequency and orientation channels adapted concurrently,” Vision Res. 28, 1303–1310 (1988).
[CrossRef]

R. L. P. Vimal, “Spatial frequency discriminations: inphase and counter-phase photopic conditions compared,” Invest. Ophthalmol. Visual Sci. Suppl. 29, 448 (1988).

1987 (1)

1986 (2)

R. L. P. Vimal, H. R. Wilson, “Spatial frequency tuning of visual mechanisms: scotopic, mesopic and photopic conditions compared,” Invest. Ophthalmol. Visual Sci. 29, 341 (1986).

M. J. Mayer, C. B. Y. Kim, “Smooth frequency discrimination functions for foveal, high-contrast, mid-spatial frequencies,” J. Opt. Soc. Am. A 3, 1957–1969 (1986) and references therein.
[CrossRef] [PubMed]

1985 (5)

1984 (4)

1983 (3)

P. H. Schiller, C. L. Colby, “The responses of single cells in the lateral geniculate nucleus of the rhesus monkey to color and luminance contrast,” Vision Res. 23, 1631–1641 (1983).
[CrossRef] [PubMed]

H. R. Wilson, D. K. McFarlane, G. C. Phillips, “Spatial frequency tuning of orientation selective units estimated by oblique masking,” Vision Res. 23, 873–882 (1983).
[CrossRef] [PubMed]

D. H. Kelly, “Spatiotemporal variation of chromatic and achromatic contrast threshold,” J. Opt. Soc. Am. 73, 742–750 (1983).
[CrossRef] [PubMed]

1982 (1)

R. L. De Valois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
[CrossRef] [PubMed]

1976 (1)

J. P. Chandler, “STEPT: direct research optimization solution of least-squares problems,” Indiana Univ. Chem. Dep. Quantum Chem. Program Exch. (QCPE) 11, 307 (1976). STEPIT is a subroutine (the original method) in STEPT.

Albrecht, D. G.

L. G. Thorell, R. L. De Valois, D. G. Albrecht, “Spatial mapping of monkey V1 cells with pure color and luminance stimuli,” Vision Res. 24, 751–769 (1984).
[CrossRef] [PubMed]

Anstis, S. M.

Barghout, L.

C. W. Tyler, L. Barghout, L. L. Kontsevich, “Surprises in analyzing the mechanisms underlying threshold elevation functions,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 819 (1993).

Blommers, P.

P. Blommers, E. F. Lindquist, Elementary Statistical Methods in Psychology and Education (Houghton Mifflin, Boston, 1960), pp. 439–440 [for expression for variance r2in Eq. (A1)].

Bradley, A.

E. Switkes, A. Bradley, K. K. De Valois, “Contrast dependence and mechanisms of masking interactions among chromatic and luminance gratings,” J. Opt. Soc. Am. A 5, 1149–1162 (1988).
[CrossRef] [PubMed]

A. Bradley, E. Switkes, K. De Valois, “Orientation and spatial frequency selectivity of adaptation to color and luminance gratings,” Vision Res. 28, 841–856 (1988).
[CrossRef] [PubMed]

Brainard, D. H.

C. Chen, J. M. Foley, D. H. Brainard, “Detection of chromoluminance patterns on chromoluminance pedestals. II: model,” Vision Res. 40, 789–803 (2000).
[CrossRef]

Bryant, E. C.

E. C. Bryant, Statistical Analysis (McGraw-Hill, New York, 1960), pp. 113–134 for linear regression, correlation, and variance r2.

Cavanagh, P.

P. Flanagan, P. Cavanagh, O. E. Favreau, “Independent orientation-selective mechanisms for the cardinal direction of color space,” Vision Res. 30, 769–778 (1990).
[CrossRef]

P. Cavanagh, D. I. A. MacLeod, S. M. Anstis, “Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones,” J. Opt. Soc. Am. A 4, 1428–1438 (1987).
[CrossRef] [PubMed]

Chandler, J. P.

J. P. Chandler, “STEPT: direct research optimization solution of least-squares problems,” Indiana Univ. Chem. Dep. Quantum Chem. Program Exch. (QCPE) 11, 307 (1976). STEPIT is a subroutine (the original method) in STEPT.

Chaparro, A.

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

Chen, C.

C. Chen, J. M. Foley, D. H. Brainard, “Detection of chromoluminance patterns on chromoluminance pedestals. II: model,” Vision Res. 40, 789–803 (2000).
[CrossRef]

Cohen, J.

J. Welkowitz, R. B. Ewen, J. Cohen, Introductory Statistics for the Behavioral Sciences (Academic, New York, 1976), pp. 51–58 (for SD), 101–109 (for SE), 140–142 and 301 (for ttest and table), 158–166 (for correlation), 166–179 (for linear regression), and 214–219, 229–236, and 304–307 (for Fratio and table).

Colby, C. L.

P. H. Schiller, C. L. Colby, “The responses of single cells in the lateral geniculate nucleus of the rhesus monkey to color and luminance contrast,” Vision Res. 23, 1631–1641 (1983).
[CrossRef] [PubMed]

Cole, G. R.

Cropper, S. J.

K. T. Mullen, S. J. Cropper, M. A. Losada, “Absence of linear subthreshold summation between Red–Green and luminance mechanisms over a wide range of spatio-temporal conditions,” Vision Res. 37, 1157–1165 (1997).
[CrossRef] [PubMed]

De Valois, K.

A. Bradley, E. Switkes, K. De Valois, “Orientation and spatial frequency selectivity of adaptation to color and luminance gratings,” Vision Res. 28, 841–856 (1988).
[CrossRef] [PubMed]

De Valois, K. K.

De Valois, R. L.

L. G. Thorell, R. L. De Valois, D. G. Albrecht, “Spatial mapping of monkey V1 cells with pure color and luminance stimuli,” Vision Res. 24, 751–769 (1984).
[CrossRef] [PubMed]

R. L. De Valois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
[CrossRef] [PubMed]

R. L. De Valois, “Orientation and spatial frequency selectivity: properties and modular organization,” in From Pigments to Perception, A. Valberg, B. B. Lee, eds. (Plenum, New York, 1991), pp. 261–267.

DeValois, R. L.

Eskew, R. T.

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

Ewen, R. B.

J. Welkowitz, R. B. Ewen, J. Cohen, Introductory Statistics for the Behavioral Sciences (Academic, New York, 1976), pp. 51–58 (for SD), 101–109 (for SE), 140–142 and 301 (for ttest and table), 158–166 (for correlation), 166–179 (for linear regression), and 214–219, 229–236, and 304–307 (for Fratio and table).

Favreau, O. E.

P. Flanagan, P. Cavanagh, O. E. Favreau, “Independent orientation-selective mechanisms for the cardinal direction of color space,” Vision Res. 30, 769–778 (1990).
[CrossRef]

Flanagan, P.

P. Flanagan, P. Cavanagh, O. E. Favreau, “Independent orientation-selective mechanisms for the cardinal direction of color space,” Vision Res. 30, 769–778 (1990).
[CrossRef]

Foley, J. M.

C. Chen, J. M. Foley, D. H. Brainard, “Detection of chromoluminance patterns on chromoluminance pedestals. II: model,” Vision Res. 40, 789–803 (2000).
[CrossRef]

Gelb, D. J.

Greenlee, M. W.

M. W. Greenlee, S. Magnussen, “Interaction among spatial frequency and orientation channels adapted concurrently,” Vision Res. 28, 1303–1310 (1988).
[CrossRef]

Hays, W.

W. Hays, Statistics, 2nd ed. (Harcourt, Brace, New York, 1994), pp. 597–637 (for linear regression and Fratio), 602 and 624 (for linear regression coefficient b), 635 (for Fratio), and 1014–1015 (for F-ratio table).

Hepler, N.

R. L. De Valois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
[CrossRef] [PubMed]

Hine, T.

Hirsch, J.

Kelly, D. H.

Kim, C. B. Y.

Kontsevich, L. L.

C. W. Tyler, L. Barghout, L. L. Kontsevich, “Surprises in analyzing the mechanisms underlying threshold elevation functions,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 819 (1993).

Krauskopf, J.

P. Lennie, J. Krauskopf, G. Sclar, “Chromatic mechanisms in striate cortex of macaque,” J. Neurosci. 10, 649–669 (1990).
[PubMed]

Kronauer, R. E.

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

Kulikowski, J. J.

J. J. Kulikowski, “What really limits vision? Conceptual limitations to the assessments of visual functions and the role of interacting channels,” in Limits of Vision, Vol. 5 of Vision and Visual Dysfunctions, J. J. Kulikowski, V. Walsh, I. J. Murray, eds. (Macmillan, London, 1991), pp. 286–329.

Lee, B. B.

B. B. Lee, J. Pokorny, V. C. Smith, P. R. Martin, A. Valberg, “Luminance and chromatic modulation sensitivity of macaque ganglion cells and human observers,” J. Opt. Soc. Am. A 7, 2223–2236 (1990).
[CrossRef] [PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque,” J. Neurosci. 9, 1433–1442 (1989).
[PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Sensitivity of macaque retinal ganglion cells to chromatic and luminance flicker,” J. Physiol. (London) 414, 223–244 (1989).

Lehky, S. R.

Lennie, P.

P. Lennie, J. Krauskopf, G. Sclar, “Chromatic mechanisms in striate cortex of macaque,” J. Neurosci. 10, 649–669 (1990).
[PubMed]

Lindquist, E. F.

P. Blommers, E. F. Lindquist, Elementary Statistical Methods in Psychology and Education (Houghton Mifflin, Boston, 1960), pp. 439–440 [for expression for variance r2in Eq. (A1)].

Losada, M. A.

K. T. Mullen, S. J. Cropper, M. A. Losada, “Absence of linear subthreshold summation between Red–Green and luminance mechanisms over a wide range of spatio-temporal conditions,” Vision Res. 37, 1157–1165 (1997).
[CrossRef] [PubMed]

M. A. Losada, K. T. Mullen, “The spatial tuning of chromatic mechanisms identified by simultaneous masking,” Vision Res. 34, 331–334 (1994).
[CrossRef] [PubMed]

K. T. Mullen, M. A. Losada, “Evidence for separate pathways for color and luminance detection mechanisms,” J. Opt. Soc. Am. A 11, 3136–3151 (1994).
[CrossRef]

MacLeod, D. I. A.

Magnussen, S.

M. W. Greenlee, S. Magnussen, “Interaction among spatial frequency and orientation channels adapted concurrently,” Vision Res. 28, 1303–1310 (1988).
[CrossRef]

Martin, P. R.

B. B. Lee, J. Pokorny, V. C. Smith, P. R. Martin, A. Valberg, “Luminance and chromatic modulation sensitivity of macaque ganglion cells and human observers,” J. Opt. Soc. Am. A 7, 2223–2236 (1990).
[CrossRef] [PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Sensitivity of macaque retinal ganglion cells to chromatic and luminance flicker,” J. Physiol. (London) 414, 223–244 (1989).

B. B. Lee, P. R. Martin, A. Valberg, “Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque,” J. Neurosci. 9, 1433–1442 (1989).
[PubMed]

Mayer, M. J.

McFarlane, D. K.

H. R. Wilson, D. K. McFarlane, G. C. Phillips, “Spatial frequency tuning of orientation selective units estimated by oblique masking,” Vision Res. 23, 873–882 (1983).
[CrossRef] [PubMed]

McIlhagga, W.

Morgan, M. J.

J. Ross, H. R. Speed, M. J. Morgan, “The effects of adaptation and masking on incremental threshold for contrast,” Vision Res. 33, 2051–2056 (1993).
[CrossRef] [PubMed]

Mullen, K. T.

K. T. Mullen, S. J. Cropper, M. A. Losada, “Absence of linear subthreshold summation between Red–Green and luminance mechanisms over a wide range of spatio-temporal conditions,” Vision Res. 37, 1157–1165 (1997).
[CrossRef] [PubMed]

M. A. Losada, K. T. Mullen, “The spatial tuning of chromatic mechanisms identified by simultaneous masking,” Vision Res. 34, 331–334 (1994).
[CrossRef] [PubMed]

K. T. Mullen, M. A. Losada, “Evidence for separate pathways for color and luminance detection mechanisms,” J. Opt. Soc. Am. A 11, 3136–3151 (1994).
[CrossRef]

K. T. Mullen, “The contrast sensitivity of human colour vision to red/green and blue/yellow chromatic gratings,” J. Physiol. (London) 359, 381–400 (1985).

Pandey, R.

R. Pandey, R. L. P. Vimal, “Spatial frequency tuned mechanisms of the Red–Green channel estimated by oblique masking,” Soc. Neurosci. Abstr. 20 (Part 2), 1580 (1994).

R. Pandey, R. L. P. Vimal, “Threshold elevation curves for the Red–Green channel estimated by oblique masking,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 751 (1993).

R. L. P. Vimal, R. Pandey, “In search of a spatial low-pass mechanism for sustained chromatic contrast sensitivity function by masking,” Invest. Ophthalmol. Visual Sci. Suppl. 33, 704 (1992).

R. L. P. Vimal, R. Pandey, “Spatial frequency discrimination for inphase and counter-phase red–green stimuli: effect of apparent motion,” Soc. Neurosci. Abstr. 15, 625 (1989).

R. Pandey, R. L. P. Vimal, “Comparison of adult threshold elevation curves of the Red–Green channel with those of an 11-year-old boy by oblique masking,” in OSA Annual Meeting, Vol. 16 of 1993 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1993), p. 130.

Phillips, G. C.

Pokorny, J.

Pokorny, J. M.

R. L. P. Vimal, J. M. Pokorny, V. C. Smith, S. K. Shevell, “Foveal cone thresholds,” Vision Res. 29, 61–78 (1989).
[CrossRef] [PubMed]

Ross, J.

J. Ross, H. R. Speed, M. J. Morgan, “The effects of adaptation and masking on incremental threshold for contrast,” Vision Res. 33, 2051–2056 (1993).
[CrossRef] [PubMed]

J. Ross, H. R. Speed, “Contrast adaptation and contrast masking in human vision,” Proc. R. Soc. London Ser. B 246, 61–69 (1991).
[CrossRef]

Ryu, A.

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

Schiller, P. H.

P. H. Schiller, C. L. Colby, “The responses of single cells in the lateral geniculate nucleus of the rhesus monkey to color and luminance contrast,” Vision Res. 23, 1631–1641 (1983).
[CrossRef] [PubMed]

Sclar, G.

P. Lennie, J. Krauskopf, G. Sclar, “Chromatic mechanisms in striate cortex of macaque,” J. Neurosci. 10, 649–669 (1990).
[PubMed]

Shevell, S. K.

R. L. P. Vimal, J. M. Pokorny, V. C. Smith, S. K. Shevell, “Foveal cone thresholds,” Vision Res. 29, 61–78 (1989).
[CrossRef] [PubMed]

Smith, V. C.

Speed, H. R.

J. Ross, H. R. Speed, M. J. Morgan, “The effects of adaptation and masking on incremental threshold for contrast,” Vision Res. 33, 2051–2056 (1993).
[CrossRef] [PubMed]

J. Ross, H. R. Speed, “Contrast adaptation and contrast masking in human vision,” Proc. R. Soc. London Ser. B 246, 61–69 (1991).
[CrossRef]

Stromeyer, C. F.

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

Switkes, E.

A. Bradley, E. Switkes, K. De Valois, “Orientation and spatial frequency selectivity of adaptation to color and luminance gratings,” Vision Res. 28, 841–856 (1988).
[CrossRef] [PubMed]

E. Switkes, A. Bradley, K. K. De Valois, “Contrast dependence and mechanisms of masking interactions among chromatic and luminance gratings,” J. Opt. Soc. Am. A 5, 1149–1162 (1988).
[CrossRef] [PubMed]

Switkes, K.

Thorell, L. G.

L. G. Thorell, R. L. De Valois, D. G. Albrecht, “Spatial mapping of monkey V1 cells with pure color and luminance stimuli,” Vision Res. 24, 751–769 (1984).
[CrossRef] [PubMed]

Tyler, C. W.

C. W. Tyler, L. Barghout, L. L. Kontsevich, “Surprises in analyzing the mechanisms underlying threshold elevation functions,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 819 (1993).

Valberg, A.

B. B. Lee, J. Pokorny, V. C. Smith, P. R. Martin, A. Valberg, “Luminance and chromatic modulation sensitivity of macaque ganglion cells and human observers,” J. Opt. Soc. Am. A 7, 2223–2236 (1990).
[CrossRef] [PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque,” J. Neurosci. 9, 1433–1442 (1989).
[PubMed]

B. B. Lee, P. R. Martin, A. Valberg, “Sensitivity of macaque retinal ganglion cells to chromatic and luminance flicker,” J. Physiol. (London) 414, 223–244 (1989).

Vimal, R. L. P.

R. L. P. Vimal, “Spatial color contrast matching: broad-bandpass functions and the flattening effect,” Vision Res. 40, 3231–3243 (2000).
[CrossRef] [PubMed]

R. L. P. Vimal, “Spatial frequency tuning of sustained non-oriented units of the Red–Green channel,” J. Opt. Soc. Am. A 15, 1–15 (1998).
[CrossRef]

R. L. P. Vimal, “Color-luminance interaction: data produced by oblique cross-masking,” J. Opt. Soc. Am. A 15, 1756–1766 (1998).
[CrossRef]

R. L. P. Vimal, “Orientation tuning of the spatial frequency tuned mechanisms of the Red–Green channel,” J. Opt. Soc. Am. A 14, 2622–2632 (1997).
[CrossRef]

R. Pandey, R. L. P. Vimal, “Spatial frequency tuned mechanisms of the Red–Green channel estimated by oblique masking,” Soc. Neurosci. Abstr. 20 (Part 2), 1580 (1994).

R. Pandey, R. L. P. Vimal, “Threshold elevation curves for the Red–Green channel estimated by oblique masking,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 751 (1993).

R. L. P. Vimal, R. Pandey, “In search of a spatial low-pass mechanism for sustained chromatic contrast sensitivity function by masking,” Invest. Ophthalmol. Visual Sci. Suppl. 33, 704 (1992).

R. L. P. Vimal, J. M. Pokorny, V. C. Smith, S. K. Shevell, “Foveal cone thresholds,” Vision Res. 29, 61–78 (1989).
[CrossRef] [PubMed]

R. L. P. Vimal, R. Pandey, “Spatial frequency discrimination for inphase and counter-phase red–green stimuli: effect of apparent motion,” Soc. Neurosci. Abstr. 15, 625 (1989).

R. L. P. Vimal, “Spatial frequency discriminations: inphase and counter-phase photopic conditions compared,” Invest. Ophthalmol. Visual Sci. Suppl. 29, 448 (1988).

R. L. P. Vimal, H. R. Wilson, “Spatial frequency tuning of visual mechanisms: scotopic, mesopic and photopic conditions compared,” Invest. Ophthalmol. Visual Sci. 29, 341 (1986).

R. Pandey, R. L. P. Vimal, “Comparison of adult threshold elevation curves of the Red–Green channel with those of an 11-year-old boy by oblique masking,” in OSA Annual Meeting, Vol. 16 of 1993 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1993), p. 130.

Webster, M. A.

Welkowitz, J.

J. Welkowitz, R. B. Ewen, J. Cohen, Introductory Statistics for the Behavioral Sciences (Academic, New York, 1976), pp. 51–58 (for SD), 101–109 (for SE), 140–142 and 301 (for ttest and table), 158–166 (for correlation), 166–179 (for linear regression), and 214–219, 229–236, and 304–307 (for Fratio and table).

Westheimer, G.

Wilson, H. R.

R. L. P. Vimal, H. R. Wilson, “Spatial frequency tuning of visual mechanisms: scotopic, mesopic and photopic conditions compared,” Invest. Ophthalmol. Visual Sci. 29, 341 (1986).

G. C. Phillips, H. R. Wilson, “Orientation bandwidths of spatial mechanisms measured by masking,” J. Opt. Soc. Am. A 1, 226–232 (1984).
[CrossRef] [PubMed]

G. C. Phillips, H. R. Wilson, “Orientation bandwidths of spatial mechanisms measured by masking,” J. Opt. Soc. Am. A 1, 226–232 (1984).
[CrossRef] [PubMed]

H. R. Wilson, D. J. Gelb, “Modified line-element theory for spatial-frequency and width discrimination,” J. Opt. Soc. Am. A 1, 124–131 (1984).
[CrossRef] [PubMed]

H. R. Wilson, D. K. McFarlane, G. C. Phillips, “Spatial frequency tuning of orientation selective units estimated by oblique masking,” Vision Res. 23, 873–882 (1983).
[CrossRef] [PubMed]

Yund, E. W.

R. L. De Valois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
[CrossRef] [PubMed]

Indiana Univ. Chem. Dep. Quantum Chem. Program Exch. (QCPE) (1)

J. P. Chandler, “STEPT: direct research optimization solution of least-squares problems,” Indiana Univ. Chem. Dep. Quantum Chem. Program Exch. (QCPE) 11, 307 (1976). STEPIT is a subroutine (the original method) in STEPT.

Invest. Ophthalmol. Visual Sci. (1)

R. L. P. Vimal, H. R. Wilson, “Spatial frequency tuning of visual mechanisms: scotopic, mesopic and photopic conditions compared,” Invest. Ophthalmol. Visual Sci. 29, 341 (1986).

Invest. Ophthalmol. Visual Sci. Suppl. (4)

R. Pandey, R. L. P. Vimal, “Threshold elevation curves for the Red–Green channel estimated by oblique masking,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 751 (1993).

R. L. P. Vimal, R. Pandey, “In search of a spatial low-pass mechanism for sustained chromatic contrast sensitivity function by masking,” Invest. Ophthalmol. Visual Sci. Suppl. 33, 704 (1992).

C. W. Tyler, L. Barghout, L. L. Kontsevich, “Surprises in analyzing the mechanisms underlying threshold elevation functions,” Invest. Ophthalmol. Visual Sci. Suppl. 34, 819 (1993).

R. L. P. Vimal, “Spatial frequency discriminations: inphase and counter-phase photopic conditions compared,” Invest. Ophthalmol. Visual Sci. Suppl. 29, 448 (1988).

J. Neurosci. (2)

B. B. Lee, P. R. Martin, A. Valberg, “Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque,” J. Neurosci. 9, 1433–1442 (1989).
[PubMed]

P. Lennie, J. Krauskopf, G. Sclar, “Chromatic mechanisms in striate cortex of macaque,” J. Neurosci. 10, 649–669 (1990).
[PubMed]

J. Opt. Soc. Am. (1)

J. Opt. Soc. Am. A (17)

P. Cavanagh, D. I. A. MacLeod, S. M. Anstis, “Equiluminance: spatial and temporal factors and the contribution of blue-sensitive cones,” J. Opt. Soc. Am. A 4, 1428–1438 (1987).
[CrossRef] [PubMed]

B. B. Lee, J. Pokorny, V. C. Smith, P. R. Martin, A. Valberg, “Luminance and chromatic modulation sensitivity of macaque ganglion cells and human observers,” J. Opt. Soc. Am. A 7, 2223–2236 (1990).
[CrossRef] [PubMed]

G. C. Phillips, H. R. Wilson, “Orientation bandwidths of spatial mechanisms measured by masking,” J. Opt. Soc. Am. A 1, 226–232 (1984).
[CrossRef] [PubMed]

S. R. Lehky, “Temporal properties of visual channels measured by masking,” J. Opt. Soc. Am. A 2, 1260–1272 (1985).
[CrossRef] [PubMed]

G. R. Cole, T. Hine, W. McIlhagga, “Detection mechanisms in L-, M- and S-cone contrast space,” J. Opt. Soc. Am. A 10, 38–51 (1993).
[CrossRef] [PubMed]

R. L. P. Vimal, “Spatial frequency tuning of sustained non-oriented units of the Red–Green channel,” J. Opt. Soc. Am. A 15, 1–15 (1998).
[CrossRef]

R. L. P. Vimal, “Orientation tuning of the spatial frequency tuned mechanisms of the Red–Green channel,” J. Opt. Soc. Am. A 14, 2622–2632 (1997).
[CrossRef]

G. C. Phillips, H. R. Wilson, “Orientation bandwidths of spatial mechanisms measured by masking,” J. Opt. Soc. Am. A 1, 226–232 (1984).
[CrossRef] [PubMed]

R. L. P. Vimal, “Color-luminance interaction: data produced by oblique cross-masking,” J. Opt. Soc. Am. A 15, 1756–1766 (1998).
[CrossRef]

K. T. Mullen, M. A. Losada, “Evidence for separate pathways for color and luminance detection mechanisms,” J. Opt. Soc. Am. A 11, 3136–3151 (1994).
[CrossRef]

E. Switkes, A. Bradley, K. K. De Valois, “Contrast dependence and mechanisms of masking interactions among chromatic and luminance gratings,” J. Opt. Soc. Am. A 5, 1149–1162 (1988).
[CrossRef] [PubMed]

M. A. Webster, K. K. De Valois, K. Switkes, “Orientation and spatial-frequency discrimination for luminance and chromatic gratings,” J. Opt. Soc. Am. A 7, 1034–1049 (1990).
[CrossRef] [PubMed]

M. A. Webster, R. L. DeValois, “Relationship between spatial-frequency and orientation tuning of striate-cortex cells,” J. Opt. Soc. Am. A 2, 1124–1132 (1985).
[CrossRef] [PubMed]

H. R. Wilson, D. J. Gelb, “Modified line-element theory for spatial-frequency and width discrimination,” J. Opt. Soc. Am. A 1, 124–131 (1984).
[CrossRef] [PubMed]

J. Hirsch, “Comment on ‘Line-separation discrimination curve in the human fovea: smooth or segmented?’,” J. Opt. Soc. Am. A 2, 477–478 (1985) and references therein.
[CrossRef] [PubMed]

G. Westheimer, “Reply to ‘Comment on “Line separation discrimination curve in the human fovea: smooth or segmented?”’” J. Opt. Soc. Am. A 2, 479 (1985) and references therein.
[CrossRef]

M. J. Mayer, C. B. Y. Kim, “Smooth frequency discrimination functions for foveal, high-contrast, mid-spatial frequencies,” J. Opt. Soc. Am. A 3, 1957–1969 (1986) and references therein.
[CrossRef] [PubMed]

J. Physiol. (London) (3)

C. F. Stromeyer, R. E. Kronauer, A. Ryu, A. Chaparro, R. T. Eskew, “Contribution of human long-wave and middle-wave cones to motion detection,” J. Physiol. (London) 485, 221–243 (1995) and relevant references therein.

K. T. Mullen, “The contrast sensitivity of human colour vision to red/green and blue/yellow chromatic gratings,” J. Physiol. (London) 359, 381–400 (1985).

B. B. Lee, P. R. Martin, A. Valberg, “Sensitivity of macaque retinal ganglion cells to chromatic and luminance flicker,” J. Physiol. (London) 414, 223–244 (1989).

Proc. R. Soc. London Ser. B (1)

J. Ross, H. R. Speed, “Contrast adaptation and contrast masking in human vision,” Proc. R. Soc. London Ser. B 246, 61–69 (1991).
[CrossRef]

Soc. Neurosci. Abstr. (2)

R. Pandey, R. L. P. Vimal, “Spatial frequency tuned mechanisms of the Red–Green channel estimated by oblique masking,” Soc. Neurosci. Abstr. 20 (Part 2), 1580 (1994).

R. L. P. Vimal, R. Pandey, “Spatial frequency discrimination for inphase and counter-phase red–green stimuli: effect of apparent motion,” Soc. Neurosci. Abstr. 15, 625 (1989).

Vision Res. (14)

P. H. Schiller, C. L. Colby, “The responses of single cells in the lateral geniculate nucleus of the rhesus monkey to color and luminance contrast,” Vision Res. 23, 1631–1641 (1983).
[CrossRef] [PubMed]

A. Bradley, E. Switkes, K. De Valois, “Orientation and spatial frequency selectivity of adaptation to color and luminance gratings,” Vision Res. 28, 841–856 (1988).
[CrossRef] [PubMed]

R. L. P. Vimal, “Spatial color contrast matching: broad-bandpass functions and the flattening effect,” Vision Res. 40, 3231–3243 (2000).
[CrossRef] [PubMed]

M. A. Losada, K. T. Mullen, “The spatial tuning of chromatic mechanisms identified by simultaneous masking,” Vision Res. 34, 331–334 (1994).
[CrossRef] [PubMed]

J. Ross, H. R. Speed, M. J. Morgan, “The effects of adaptation and masking on incremental threshold for contrast,” Vision Res. 33, 2051–2056 (1993).
[CrossRef] [PubMed]

R. L. P. Vimal, J. M. Pokorny, V. C. Smith, S. K. Shevell, “Foveal cone thresholds,” Vision Res. 29, 61–78 (1989).
[CrossRef] [PubMed]

H. R. Wilson, D. K. McFarlane, G. C. Phillips, “Spatial frequency tuning of orientation selective units estimated by oblique masking,” Vision Res. 23, 873–882 (1983).
[CrossRef] [PubMed]

A. Chaparro, C. F. Stromeyer, R. E. Kronauer, R. T. Eskew, “Separable Red–Green and luminance detectors for small flashes,” Vision Res. 34, 751–762 (1994) and relevant references therein.
[CrossRef] [PubMed]

K. T. Mullen, S. J. Cropper, M. A. Losada, “Absence of linear subthreshold summation between Red–Green and luminance mechanisms over a wide range of spatio-temporal conditions,” Vision Res. 37, 1157–1165 (1997).
[CrossRef] [PubMed]

P. Flanagan, P. Cavanagh, O. E. Favreau, “Independent orientation-selective mechanisms for the cardinal direction of color space,” Vision Res. 30, 769–778 (1990).
[CrossRef]

M. W. Greenlee, S. Magnussen, “Interaction among spatial frequency and orientation channels adapted concurrently,” Vision Res. 28, 1303–1310 (1988).
[CrossRef]

L. G. Thorell, R. L. De Valois, D. G. Albrecht, “Spatial mapping of monkey V1 cells with pure color and luminance stimuli,” Vision Res. 24, 751–769 (1984).
[CrossRef] [PubMed]

R. L. De Valois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
[CrossRef] [PubMed]

C. Chen, J. M. Foley, D. H. Brainard, “Detection of chromoluminance patterns on chromoluminance pedestals. II: model,” Vision Res. 40, 789–803 (2000).
[CrossRef]

Other (7)

R. Pandey, R. L. P. Vimal, “Comparison of adult threshold elevation curves of the Red–Green channel with those of an 11-year-old boy by oblique masking,” in OSA Annual Meeting, Vol. 16 of 1993 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1993), p. 130.

J. J. Kulikowski, “What really limits vision? Conceptual limitations to the assessments of visual functions and the role of interacting channels,” in Limits of Vision, Vol. 5 of Vision and Visual Dysfunctions, J. J. Kulikowski, V. Walsh, I. J. Murray, eds. (Macmillan, London, 1991), pp. 286–329.

J. Welkowitz, R. B. Ewen, J. Cohen, Introductory Statistics for the Behavioral Sciences (Academic, New York, 1976), pp. 51–58 (for SD), 101–109 (for SE), 140–142 and 301 (for ttest and table), 158–166 (for correlation), 166–179 (for linear regression), and 214–219, 229–236, and 304–307 (for Fratio and table).

W. Hays, Statistics, 2nd ed. (Harcourt, Brace, New York, 1994), pp. 597–637 (for linear regression and Fratio), 602 and 624 (for linear regression coefficient b), 635 (for Fratio), and 1014–1015 (for F-ratio table).

R. L. De Valois, “Orientation and spatial frequency selectivity: properties and modular organization,” in From Pigments to Perception, A. Valberg, B. B. Lee, eds. (Plenum, New York, 1991), pp. 261–267.

P. Blommers, E. F. Lindquist, Elementary Statistical Methods in Psychology and Education (Houghton Mifflin, Boston, 1960), pp. 439–440 [for expression for variance r2in Eq. (A1)].

E. C. Bryant, Statistical Analysis (McGraw-Hill, New York, 1960), pp. 113–134 for linear regression, correlation, and variance r2.

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Figures (7)

Fig. 1
Fig. 1

Threshold elevation (TE) versus mask spatial frequency (SF), or (TvSF), curves peaking at approximately 0.13 cpd for observers RV (upper plot) and RP (lower plot) at 60% mask contrast. The symbols represent the data, and the curves represent the best fit. The TvSF curves with test spatial frequencies (arrows) are 0.0625 cpd (open circles and solid curves), 0.088 cpd (crosses and dashed curves), 0.125 cpd (large solid circles and solid curves), 0.177 cpd (small solid circles and dashed curves), 0.25 cpd (asterisks and dashed curves), and 0.35 cpd (open circles and dashed curves). Error bars: 1 standard error (SE). The shapes and/or the bandwidths of the TvSF curves are not similar (though they all peak at approximately 0.13 cpd), suggesting that more than a single mechanism would be necessary to explain the data. For detail see Subsection 3.C.

Fig. 2
Fig. 2

TvSF curves for observers RV [left-hand plots in (a) and (b)] and RP [right-hand plots in (a) and (b)] at 60% mask contrast. Dashed and solid curves represent the best fits to the data indicated by open circles and solid circles, respectively. Symbols with a downward arrow indicate the test SFs, which are also placed onto the plots. Error bars: 1 SE. In (a) TvSFs for low test SFs of 0.0625–0.35 are plotted, and in (b) TvSFs for higher test SFs of 0.5–8 cpd are shown. For detail see Subsections 3.C and 4.A.

Fig. 3
Fig. 3

TE versus mask contrast in times threshold metric, or TvC, curves on log–log coordinates for observers RV (left-hand plots) and RP (right-hand plots). The mask contrasts were (1) 1.2% (at 0.0625 and 0.125 cpd for both subjects; at 0.25, 0.35, and 0.5 cpd for RP), 1.6% (at 0.25 cpd for RV), and 1.8% (at 0.5 cpd for RV) and (2) 6.25%, 12.5%, 25%, and 60% for all conditions. In addition, a mask contrast of 42% was used at 1 and 8 cpd for RP. Test SF = mask SF; SFs are placed onto the plots. Thin dashed, solid, and thick dashed curves represent the best fits to the data indicated by open circles, solid circles, and crosses, respectively. Dotted lines indicate no masking (TE=1). Error bars: 1 SE. For detail see Subsections 3.D and 4.A.

Fig. 4
Fig. 4

SF-tuned mechanisms of the Red–Green channel plotted as normalized sensitivity (to a peak value of unity) versus SF. The SF-tuned oblique-masking color mechanisms (C1: low pass; for C2, C3, C4, C5, and C6, the filters peak at 0.13, 0.5, 2, 4 and 8 cpd, respectively) are plotted for RV (filled circles) and RP (open circles). The solid curves represent the geometric mean over RV, RP, DH (Ref. 6), and KTM (Refs. 7, 12, and 13); data for KTM and DH are not plotted; for detail see Subsection 4.A. The dashed curves (which mostly overlap with the solid curves) indicate the color mechanisms extracted by obtaining the best fit to the data averaged over RV and RP. The dotted curves (which also mostly overlap with symbols, solid curves, and dashed curves) represent the color mechanisms extracted by obtaining the best fit to the data averaged over RV and RP when oblique- and orthogonal-masking data are combined and an additional six gain factors for orthogonal-masking data with respect to oblique masking are included. The dotted lines are drawn at 0.5 for visualizing the half-height bandwidths. For detail see Subsections 4.A and 5.B.

Fig. 5
Fig. 5

Statistics plotted as a function of the number of color mechanisms for observers RV (solid circles and solid curves) and RP (open circles and dashed curves); dotted curves represent the average of the plotted statistics. Top left: the F ratio is plotted for the linear regression between data and fit for RV, RP, and the average. The average F ratio increases as the number of mechanism increases. Bottom left: the correlation (“corr. r”) of the data and the best fits are plotted. On average, r increases as the number of mechanisms increases. Top right: the model selection criterion (MSC) peaks at 6, suggesting that the optimum number of mechanisms is 6. Bottom right: the absolute error (“abs. err.”) statistics decrease with an increase in number of mechanisms. A plateau is reached at approximately 6, which is taken as the minimum number of mechanisms. For detail see Subsections 4.A and 4.C.

Fig. 6
Fig. 6

Normalized fit (on y axis) as a function of normalized data (on x axis). For both data and fit, contrast sensitivities were normalized with respect to the maximum contrast sensitivity (RV: 74.78, RP: 92.94) of contrast sensitivity function data, and TEs were normalized with respect to the maximum TE (RV: 6.87, RP: 5.67) of TE data for a subject. Solid circles (RV) and open circles (RP) represent the data. The solid line (RV: y=0.053+0.831x) and the dashed line (RP: y=0.089+0.787x) represent the linear regression between data and fit. The dotted line along 45° (unity slope) represents the condition data = fit. Correlation r=0.915 (RV) and 0.898 (RP). For detail see Subsection 4.A.

Fig. 7
Fig. 7

Full bandwidths at half-height of mechanisms plotted as a function of peak SF of the tuning functions. Solid circles represent bandwidths for RV (color), open circles are for RP (color), and asterisks are for the cortical color cells of monkey.23,24 The thick solid curve represent bandwidths for the geometric mean of RV, RP, DH (Ref. 6), and KTM (Refs. 7, 12, and 13) (see Subsection 4.A) for the color channel, the thin solid curve is for the six bandpass mechanisms of the achromatic channel,2 and the dashed curve is for the cortical achromatic cells of monkey.25 In general, the chromatic and achromatic bandwidths decrease with an increase in peak SF. For detail see Subsections 4.A and 4.B.

Tables (2)

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Table 1 Parameters for the Color Mechanisms of Combined Oblique and Orthogonal Masking for RV and RP, and Average of RV and RP for Oblique Masking Alonea

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Table 2 Statistics for Model Fits a

Equations (9)

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r2=(regressionSS)/[(regressionSS)+(residualSS)],
(regressionSS)/(residualSS)=[r2/(1-r2)].
 r=[fit - mean(fit)][data - mean(data)]/
[fit - mean(fit)]2[data - mean(data)]21/2.
y=a+bx,
b=r[fit - mean(fit)]2/[data - mean(data)]21/2,
a=mean(fit)-b mean(data),
F ratio=(regressionSS)/(regressionDF)(residualSS)/(residualDF),
Fratio=[(Nd-Nr)/(Nr-1)][r2/(1-r2)]=(Nd-2)[r2/(1-r2)],

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