Abstract

The perceived contrast of a pulsed grating varies markedly with the exposure duration and spatial frequency of the grating. We studied dynamic changes in perceived grating contrast with a pattern-masking paradigm. We measured masking of a brief, localized test pattern (a D6 stimulus, 30 ms in duration) by fixed-contrast cosine grating patterns of varying duration (50–500 ms). The cosine mask pattern had spatial frequency of either 1 or 6 cycles per degree (cpd) at a contrast of 0.3. The D6 test pattern was centered on a light bar of the mask and was either positive peak contrast (same-polarity test and mask) or negative peak contrast (opposite-polarity test and mask). In Experiment 1, the test and mask had simultaneous onset. With a 6-cpd mask, the same-polarity test-threshold elevation versus mask-duration function increases monotonically. For a 1-cpd mask, the same-polarity threshold–mask-duration function is nonmonotonic, with peak masking effect produced by a grating pulse of 80–100 ms. These masking effects are closely congruent with known dynamic contrast effects. With negative tests, masking-duration functions are elevated from same-polarity functions and are essentially similar in shape for 1- and 6-cpd masks. The elevated thresholds suggest inhibitory interaction between ON and OFF pathways, with a similar time course across spatial frequency. In Experiment 2, the D6 test was delayed from mask onset by 33 ms. Positive contrasts only were employed. For 1-cpd stimuli, the delay of test greatly reduced masking at all mask durations and eliminated the nonmonotonic function. This suggests that for low-spatial-frequency patterns, perceived contrast is determined by an early peak component of the neural response. But for 6-cpd stimuli, masking of the delayed test was somewhat greater at all mask durations, consistent with a gradually increasing underlying neural response to the grating. Finally, in Experiment 3, same-polarity masking effects at both spatial frequencies were replicated with negative-contrast test and mask (OFF pathway mediation). This indicates that the ON and OFF pathways have similar response dynamics.

© 1998 Optical Society of America

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References

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  1. F. L. Kitterle, T. R. Corwin, “Enhancement of apparent contrast in flashed sinusoidal gratings,” Vision Res. 19, 33–39 (1979).
    [CrossRef] [PubMed]
  2. A. Broca, P. Sulzer, “La sensation lumineuse en function du temps,” J. Physiol. Pathol. Gen. 6, 55–68 (1903).
  3. R. W. Bowen, K. A. Markell, “Temporal brightness enhancement studied with a large sample of observers: evidence for individual differences in brightness perception,” Percept. Psychophys. 27, 465–476 (1980).
    [CrossRef] [PubMed]
  4. H. de Ridder, “Dynamic properties of human brightness perception,” Ph.D. dissertation (Eindhoven University of Technology, Eindhoven, The Netherlands, 1987).
  5. J. A. J. Roufs, F. J. J. Blommaert, “Temporal impulse and step response of the human eye obtained psychophysically by means of a drift-correcting perturbation technique,” Vision Res. 21, 1203–1221 (1981).
    [CrossRef]
  6. D. H. Hubel, T. N. Wiesel, “Receptive fields and functional architecture of monkey striate cortex,” J. Physiol. (London) 195, 215–243 (1968).
  7. 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]
  8. B. H. Crawford, “Visual adaptation in relation to brief conditioning stimuli,” Proc. R. Soc. London, Ser. B 134, 283–300 (1947).
    [CrossRef]
  9. R. W. Bowen, H. R. Wilson, “A two-process analysis of pattern masking,” Vision Res. 34, 645–657 (1994).
    [CrossRef] [PubMed]
  10. R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: pattern polarity effects on contrast discrimination,” Vision Res. 35, 2479–2490 (1995).
    [CrossRef] [PubMed]
  11. R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: contrast discrimination at pattern offset,” Vision Res. 37, 185–198 (1997).
    [CrossRef] [PubMed]
  12. P. Schiller, “The ON and OFF channels of the visual system,” Trends Neurosci. 15, 86–91 (1992).
    [CrossRef] [PubMed]
  13. R. A. Bjorklund, S. Magnussen, “Decrement versions of the Broca–Sulzer effect and its spatial analogue,” Vision Res. 19, 155–157 (1979).
    [CrossRef]
  14. R. F. Quick, “A vector-magnitude model of contrast detection,” Kybernetik 16, 1299–1302 (1974).
    [CrossRef]
  15. D. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
    [CrossRef] [PubMed]
  16. F. A. A. Kingdom, P. Whittle, “Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing,” Vision Res. 36, 817–830 (1996).
    [CrossRef] [PubMed]
  17. P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.
  18. R. Shapley, “Visual sensitivity and parallel retinocortical channels,” Ann. Rev. Psych. 41, 635–658 (1990).
    [CrossRef]
  19. M. Livingston, D. Hubel, “Psychophysical evidence for separate channels for the perception of form, color, motion and depth,” J. Neurosci. 7, 3416–3468 (1987).
  20. R. W. Bowen, J. Pokorny, “Target edge sharpness and temporal brightness enhancement,” Vision Res. 18, 1691–1695 (1978).
    [CrossRef] [PubMed]
  21. L. E. Arend, “Spatial factors in the Broca–Sulzer phenomenon,” J. Opt. Soc. Am. 63, 879–883 (1973).
    [CrossRef] [PubMed]
  22. R. W. Bowen, M. J. Nissen, “Luminance, not brightness, determines temporal brightness enhancement with chromatic stimuli,” J. Opt. Soc. Am. 69, 581–584 (1979).
    [CrossRef] [PubMed]
  23. F. L. Kitterle, T. R. Corwin, “The effects of temporal waveform upon apparent contrast,” Percept. Psychophys. 33, 72–74 (1983).
    [CrossRef] [PubMed]
  24. D. J. Heeger, “Normalization of cell responses in cat striate cortex,” Visual Neurosci. 9, 181–197 (1992).
    [PubMed]

1997 (1)

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: contrast discrimination at pattern offset,” Vision Res. 37, 185–198 (1997).
[CrossRef] [PubMed]

1996 (1)

F. A. A. Kingdom, P. Whittle, “Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing,” Vision Res. 36, 817–830 (1996).
[CrossRef] [PubMed]

1995 (1)

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: pattern polarity effects on contrast discrimination,” Vision Res. 35, 2479–2490 (1995).
[CrossRef] [PubMed]

1994 (1)

R. W. Bowen, H. R. Wilson, “A two-process analysis of pattern masking,” Vision Res. 34, 645–657 (1994).
[CrossRef] [PubMed]

1992 (3)

P. Schiller, “The ON and OFF channels of the visual system,” Trends Neurosci. 15, 86–91 (1992).
[CrossRef] [PubMed]

D. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
[CrossRef] [PubMed]

D. J. Heeger, “Normalization of cell responses in cat striate cortex,” Visual Neurosci. 9, 181–197 (1992).
[PubMed]

1990 (1)

R. Shapley, “Visual sensitivity and parallel retinocortical channels,” Ann. Rev. Psych. 41, 635–658 (1990).
[CrossRef]

1987 (1)

M. Livingston, D. Hubel, “Psychophysical evidence for separate channels for the perception of form, color, motion and depth,” J. Neurosci. 7, 3416–3468 (1987).

1983 (2)

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]

F. L. Kitterle, T. R. Corwin, “The effects of temporal waveform upon apparent contrast,” Percept. Psychophys. 33, 72–74 (1983).
[CrossRef] [PubMed]

1981 (1)

J. A. J. Roufs, F. J. J. Blommaert, “Temporal impulse and step response of the human eye obtained psychophysically by means of a drift-correcting perturbation technique,” Vision Res. 21, 1203–1221 (1981).
[CrossRef]

1980 (1)

R. W. Bowen, K. A. Markell, “Temporal brightness enhancement studied with a large sample of observers: evidence for individual differences in brightness perception,” Percept. Psychophys. 27, 465–476 (1980).
[CrossRef] [PubMed]

1979 (3)

F. L. Kitterle, T. R. Corwin, “Enhancement of apparent contrast in flashed sinusoidal gratings,” Vision Res. 19, 33–39 (1979).
[CrossRef] [PubMed]

R. A. Bjorklund, S. Magnussen, “Decrement versions of the Broca–Sulzer effect and its spatial analogue,” Vision Res. 19, 155–157 (1979).
[CrossRef]

R. W. Bowen, M. J. Nissen, “Luminance, not brightness, determines temporal brightness enhancement with chromatic stimuli,” J. Opt. Soc. Am. 69, 581–584 (1979).
[CrossRef] [PubMed]

1978 (1)

R. W. Bowen, J. Pokorny, “Target edge sharpness and temporal brightness enhancement,” Vision Res. 18, 1691–1695 (1978).
[CrossRef] [PubMed]

1974 (1)

R. F. Quick, “A vector-magnitude model of contrast detection,” Kybernetik 16, 1299–1302 (1974).
[CrossRef]

1973 (1)

1968 (1)

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

1947 (1)

B. H. Crawford, “Visual adaptation in relation to brief conditioning stimuli,” Proc. R. Soc. London, Ser. B 134, 283–300 (1947).
[CrossRef]

1903 (1)

A. Broca, P. Sulzer, “La sensation lumineuse en function du temps,” J. Physiol. Pathol. Gen. 6, 55–68 (1903).

Arend, L. E.

Bjorklund, R. A.

R. A. Bjorklund, S. Magnussen, “Decrement versions of the Broca–Sulzer effect and its spatial analogue,” Vision Res. 19, 155–157 (1979).
[CrossRef]

Blommaert, F. J. J.

J. A. J. Roufs, F. J. J. Blommaert, “Temporal impulse and step response of the human eye obtained psychophysically by means of a drift-correcting perturbation technique,” Vision Res. 21, 1203–1221 (1981).
[CrossRef]

Bowen, R. W.

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: contrast discrimination at pattern offset,” Vision Res. 37, 185–198 (1997).
[CrossRef] [PubMed]

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: pattern polarity effects on contrast discrimination,” Vision Res. 35, 2479–2490 (1995).
[CrossRef] [PubMed]

R. W. Bowen, H. R. Wilson, “A two-process analysis of pattern masking,” Vision Res. 34, 645–657 (1994).
[CrossRef] [PubMed]

R. W. Bowen, K. A. Markell, “Temporal brightness enhancement studied with a large sample of observers: evidence for individual differences in brightness perception,” Percept. Psychophys. 27, 465–476 (1980).
[CrossRef] [PubMed]

R. W. Bowen, M. J. Nissen, “Luminance, not brightness, determines temporal brightness enhancement with chromatic stimuli,” J. Opt. Soc. Am. 69, 581–584 (1979).
[CrossRef] [PubMed]

R. W. Bowen, J. Pokorny, “Target edge sharpness and temporal brightness enhancement,” Vision Res. 18, 1691–1695 (1978).
[CrossRef] [PubMed]

Broca, A.

A. Broca, P. Sulzer, “La sensation lumineuse en function du temps,” J. Physiol. Pathol. Gen. 6, 55–68 (1903).

Corwin, T. R.

F. L. Kitterle, T. R. Corwin, “The effects of temporal waveform upon apparent contrast,” Percept. Psychophys. 33, 72–74 (1983).
[CrossRef] [PubMed]

F. L. Kitterle, T. R. Corwin, “Enhancement of apparent contrast in flashed sinusoidal gratings,” Vision Res. 19, 33–39 (1979).
[CrossRef] [PubMed]

Crawford, B. H.

B. H. Crawford, “Visual adaptation in relation to brief conditioning stimuli,” Proc. R. Soc. London, Ser. B 134, 283–300 (1947).
[CrossRef]

de Ridder, H.

H. de Ridder, “Dynamic properties of human brightness perception,” Ph.D. dissertation (Eindhoven University of Technology, Eindhoven, The Netherlands, 1987).

Heeger, D. J.

D. J. Heeger, “Normalization of cell responses in cat striate cortex,” Visual Neurosci. 9, 181–197 (1992).
[PubMed]

Hubel, D.

M. Livingston, D. Hubel, “Psychophysical evidence for separate channels for the perception of form, color, motion and depth,” J. Neurosci. 7, 3416–3468 (1987).

Hubel, D. H.

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

Kingdom, F. A. A.

F. A. A. Kingdom, P. Whittle, “Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing,” Vision Res. 36, 817–830 (1996).
[CrossRef] [PubMed]

Kitterle, F. L.

F. L. Kitterle, T. R. Corwin, “The effects of temporal waveform upon apparent contrast,” Percept. Psychophys. 33, 72–74 (1983).
[CrossRef] [PubMed]

F. L. Kitterle, T. R. Corwin, “Enhancement of apparent contrast in flashed sinusoidal gratings,” Vision Res. 19, 33–39 (1979).
[CrossRef] [PubMed]

Lennie, P.

P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.

Livingston, M.

M. Livingston, D. Hubel, “Psychophysical evidence for separate channels for the perception of form, color, motion and depth,” J. Neurosci. 7, 3416–3468 (1987).

MacLeod, D. I. A.

D. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
[CrossRef] [PubMed]

Magnussen, S.

R. A. Bjorklund, S. Magnussen, “Decrement versions of the Broca–Sulzer effect and its spatial analogue,” Vision Res. 19, 155–157 (1979).
[CrossRef]

Makous, W.

D. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
[CrossRef] [PubMed]

Markell, K. A.

R. W. Bowen, K. A. Markell, “Temporal brightness enhancement studied with a large sample of observers: evidence for individual differences in brightness perception,” Percept. Psychophys. 27, 465–476 (1980).
[CrossRef] [PubMed]

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]

Nissen, M. J.

Phillips, G. C.

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]

Pokorny, J.

R. W. Bowen, J. Pokorny, “Target edge sharpness and temporal brightness enhancement,” Vision Res. 18, 1691–1695 (1978).
[CrossRef] [PubMed]

Quick, R. F.

R. F. Quick, “A vector-magnitude model of contrast detection,” Kybernetik 16, 1299–1302 (1974).
[CrossRef]

Roufs, J. A. J.

J. A. J. Roufs, F. J. J. Blommaert, “Temporal impulse and step response of the human eye obtained psychophysically by means of a drift-correcting perturbation technique,” Vision Res. 21, 1203–1221 (1981).
[CrossRef]

Schiller, P.

P. Schiller, “The ON and OFF channels of the visual system,” Trends Neurosci. 15, 86–91 (1992).
[CrossRef] [PubMed]

Shapley, R.

R. Shapley, “Visual sensitivity and parallel retinocortical channels,” Ann. Rev. Psych. 41, 635–658 (1990).
[CrossRef]

Sulzer, P.

A. Broca, P. Sulzer, “La sensation lumineuse en function du temps,” J. Physiol. Pathol. Gen. 6, 55–68 (1903).

Trevarthen, C.

P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.

van Essen, D.

P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.

Waessle, H.

P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.

Whittle, P.

F. A. A. Kingdom, P. Whittle, “Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing,” Vision Res. 36, 817–830 (1996).
[CrossRef] [PubMed]

Wiesel, T. N.

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

Williams, D. R.

D. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
[CrossRef] [PubMed]

Wilson, H. R.

R. W. Bowen, H. R. Wilson, “A two-process analysis of pattern masking,” Vision Res. 34, 645–657 (1994).
[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]

Ann. Rev. Psych. (1)

R. Shapley, “Visual sensitivity and parallel retinocortical channels,” Ann. Rev. Psych. 41, 635–658 (1990).
[CrossRef]

J. Neurosci. (1)

M. Livingston, D. Hubel, “Psychophysical evidence for separate channels for the perception of form, color, motion and depth,” J. Neurosci. 7, 3416–3468 (1987).

J. Opt. Soc. Am. (2)

J. Physiol. (London) (1)

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

J. Physiol. Pathol. Gen. (1)

A. Broca, P. Sulzer, “La sensation lumineuse en function du temps,” J. Physiol. Pathol. Gen. 6, 55–68 (1903).

Kybernetik (1)

R. F. Quick, “A vector-magnitude model of contrast detection,” Kybernetik 16, 1299–1302 (1974).
[CrossRef]

Percept. Psychophys. (2)

R. W. Bowen, K. A. Markell, “Temporal brightness enhancement studied with a large sample of observers: evidence for individual differences in brightness perception,” Percept. Psychophys. 27, 465–476 (1980).
[CrossRef] [PubMed]

F. L. Kitterle, T. R. Corwin, “The effects of temporal waveform upon apparent contrast,” Percept. Psychophys. 33, 72–74 (1983).
[CrossRef] [PubMed]

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

B. H. Crawford, “Visual adaptation in relation to brief conditioning stimuli,” Proc. R. Soc. London, Ser. B 134, 283–300 (1947).
[CrossRef]

Trends Neurosci. (1)

P. Schiller, “The ON and OFF channels of the visual system,” Trends Neurosci. 15, 86–91 (1992).
[CrossRef] [PubMed]

Vision Res. (10)

R. A. Bjorklund, S. Magnussen, “Decrement versions of the Broca–Sulzer effect and its spatial analogue,” Vision Res. 19, 155–157 (1979).
[CrossRef]

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. I. A. MacLeod, D. R. Williams, W. Makous, “A visual nonlinearity fed by single cones,” Vision Res. 32, 347–363 (1992).
[CrossRef] [PubMed]

F. A. A. Kingdom, P. Whittle, “Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing,” Vision Res. 36, 817–830 (1996).
[CrossRef] [PubMed]

R. W. Bowen, H. R. Wilson, “A two-process analysis of pattern masking,” Vision Res. 34, 645–657 (1994).
[CrossRef] [PubMed]

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: pattern polarity effects on contrast discrimination,” Vision Res. 35, 2479–2490 (1995).
[CrossRef] [PubMed]

R. W. Bowen, “Isolation and interaction of ON and OFF pathways in human vision: contrast discrimination at pattern offset,” Vision Res. 37, 185–198 (1997).
[CrossRef] [PubMed]

F. L. Kitterle, T. R. Corwin, “Enhancement of apparent contrast in flashed sinusoidal gratings,” Vision Res. 19, 33–39 (1979).
[CrossRef] [PubMed]

J. A. J. Roufs, F. J. J. Blommaert, “Temporal impulse and step response of the human eye obtained psychophysically by means of a drift-correcting perturbation technique,” Vision Res. 21, 1203–1221 (1981).
[CrossRef]

R. W. Bowen, J. Pokorny, “Target edge sharpness and temporal brightness enhancement,” Vision Res. 18, 1691–1695 (1978).
[CrossRef] [PubMed]

Visual Neurosci. (1)

D. J. Heeger, “Normalization of cell responses in cat striate cortex,” Visual Neurosci. 9, 181–197 (1992).
[PubMed]

Other (2)

H. de Ridder, “Dynamic properties of human brightness perception,” Ph.D. dissertation (Eindhoven University of Technology, Eindhoven, The Netherlands, 1987).

P. Lennie, C. Trevarthen, H. Waessle, D. van Essen, “Parallel processing of visual information,” in Visual Perception: The Neurophysiological Foundations, L. Spillman, J. Werner, eds. (Academic, New York, 1989), Chap. 6, pp. 103–128.

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Figures (3)

Fig. 1
Fig. 1

Results from Experiment 1: threshold shift versus mask-duration function. Threshold shift values are for a cortical masking process (pattern selective) calculated from Eq. (3); see text for discussion. Open circles, 1-cpd positive tests; open diamonds, 6-cpd positive tests; filled circles and diamonds are for negative 1- and 6-cpd tests, respectively. Data are for two observers: HdR (top panel) and RWB (bottom panel).

Fig. 2
Fig. 2

Results from Experiment 2 for observer RWB. Threshold shift (cortical) as a function of mask duration for positive 1- and 6-cpd test and mask (top and bottom panel). In Experiment 2, the test–mask SOA was 33 ms (open squares); data for SOA=0 ms from Experiment 1 (open circles) are shown for comparison.

Fig. 3
Fig. 3

Results from Experiment 3 for observer RWB. Threshold shift (cortical) as a function of mask duration for negative test and negative mask: 1-cpd stimuli (filled circles, top panel); 6-cpd stimuli (filled diamonds, bottom panel). Data from Experiment 1 for positive 1-cpd test and mask (open circles) and positive 6-cpd stimuli (open diamonds) are shown for comparison.

Tables (1)

Tables Icon

Table 1 Average Threshold Shift Due To Uniform Masks in the Three Experiments

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

D6=c1515-90xσ2+60xσ4-8xσ6×e -x2σx2e -y2σy2,
c=(Lext-Lmean)/Lmean,
TS(cortical)=TS(cosine)/TS(uniformfield).

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