Abstract

Recent models have attempted to reconcile low psychophysical orientation and spatial-frequency discrimination thresholds with relatively broad orientation and spatial-frequency tuning of cortical neurons. These models have relied on the ability of the neurons to convert small stimulus changes into reliable response changes. We have examined this ability in a sample of neurons from the cat’s striate cortex. We present here data from two cells that reliably signaled the smallest orientation and spatial-frequency differences. Using receiver operating characteristic analysis, we find that these cells could reliably signal orientation differences of 1.84 deg and spatial-frequency differences of 0.073 octave. We compare these single-cell results to cat and human behavioral discrimination thresholds.

© 1985 Optical Society of America

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References

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  1. F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
    [PubMed]
  2. F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
    [PubMed]
  3. R. L. DeValois, E. W. Yund, N. Hepler, “The orientation and direction selectivity of cells in macaque visual cortex,” Vision Res. 22, 531–544 (1982).
    [CrossRef]
  4. R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
    [CrossRef]
  5. F. W. Campbell, J. Nachmias, J. Jukes, “Spatial-frequency discrimination in human vision,” J. Opt. Soc. Am. 60, 555–559 (1970).
    [CrossRef] [PubMed]
  6. D. P. Andrews, “Perception of contour orientation in the central fovea. Part I: Short lines,” Vision Res. 7, 975–997 (1967).
    [CrossRef] [PubMed]
  7. J. Hirsch, R. Hylton, “Limits of spatial-frequency discrimination as evidence of neural interpolation,” J. Opt. Soc. Am. 72, 1367–1374 (1982).
    [CrossRef] [PubMed]
  8. C. A. Burbeck, D. Regan, “Independence of orientation and size in spatial discriminations,” J. Opt. Soc. Am. 73, 1691–1694 (1983).
    [CrossRef] [PubMed]
  9. A. Bradley, B. C. Skottun, “The effects of large orientation and spatial frequency differences on spatial discriminations,” Vision Res. 24, 1889–1896 (1984).
    [CrossRef] [PubMed]
  10. D. Regan, K. I. Beverley, “Spatial-frequency discrimination and detection: comparison of postadaptation thresholds,” J. Opt. Soc. Am. A 73, 1684–1690 (1984).
  11. 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]
  12. H. R. Wilson, D. Regan, “Spatial-frequency adaptation and grating discrimination: predictions of a line element model,” J. Opt. Soc. Am. A 1, 1091–1096 (1984).
    [CrossRef] [PubMed]
  13. D. Regan, K. I. Beverley, “Postadaptation orientation discrimination,” J. Opt. Soc. Am. A 2, 147–155 (1985).
    [CrossRef] [PubMed]
  14. G. Westheimer, “Visual hyperacuity,” Prog. Sensory Physiol. 1, 1–30 (1981).
    [CrossRef]
  15. R. M. Boynton, Human Color Vision (Holt, Rinehart, and Winston, New York, 1979).
  16. R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).
  17. I. P. Howard, Human Visual Orientation (Wiley, Chichester, England, 1982).
  18. B. C. Skottun, R. D. Freeman, “Stimulus specificity of binocular cells in the cat’s visual cortex: ocular dominance and the matching of left and right eyes,” Exp. Brain Res. 56, 206–216 (1984).
    [CrossRef]
  19. A. Dean, “The variability of discharge of simple cells in the cat striate cortex,” Exp. Brain Res. 44, 437–440 (1981).
    [CrossRef] [PubMed]
  20. D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
    [PubMed]
  21. D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
    [CrossRef] [PubMed]
  22. D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).
  23. T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
    [CrossRef] [PubMed]
  24. R. F. Quick, “A vector magnitude model of contrast detection,” Kybernetik 16, 65–67 (1974).
    [CrossRef]
  25. E. Vandenbussche, G. A. Orban, “Meridional variations in the line orientation discrimination of the cat,” Behavior Brain Res. 9, 237–255 (1983).
    [CrossRef]
  26. K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
    [PubMed]
  27. K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
    [PubMed]

1985 (1)

1984 (5)

B. C. Skottun, R. D. Freeman, “Stimulus specificity of binocular cells in the cat’s visual cortex: ocular dominance and the matching of left and right eyes,” Exp. Brain Res. 56, 206–216 (1984).
[CrossRef]

A. Bradley, B. C. Skottun, “The effects of large orientation and spatial frequency differences on spatial discriminations,” Vision Res. 24, 1889–1896 (1984).
[CrossRef] [PubMed]

D. Regan, K. I. Beverley, “Spatial-frequency discrimination and detection: comparison of postadaptation thresholds,” J. Opt. Soc. Am. A 73, 1684–1690 (1984).

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. Regan, “Spatial-frequency adaptation and grating discrimination: predictions of a line element model,” J. Opt. Soc. Am. A 1, 1091–1096 (1984).
[CrossRef] [PubMed]

1983 (3)

C. A. Burbeck, D. Regan, “Independence of orientation and size in spatial discriminations,” J. Opt. Soc. Am. 73, 1691–1694 (1983).
[CrossRef] [PubMed]

D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
[CrossRef] [PubMed]

E. Vandenbussche, G. A. Orban, “Meridional variations in the line orientation discrimination of the cat,” Behavior Brain Res. 9, 237–255 (1983).
[CrossRef]

1982 (3)

J. Hirsch, R. Hylton, “Limits of spatial-frequency discrimination as evidence of neural interpolation,” J. Opt. Soc. Am. 72, 1367–1374 (1982).
[CrossRef] [PubMed]

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

R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
[CrossRef]

1981 (5)

A. Dean, “The variability of discharge of simple cells in the cat striate cortex,” Exp. Brain Res. 44, 437–440 (1981).
[CrossRef] [PubMed]

D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
[PubMed]

G. Westheimer, “Visual hyperacuity,” Prog. Sensory Physiol. 1, 1–30 (1981).
[CrossRef]

K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
[PubMed]

K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
[PubMed]

1975 (1)

T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
[CrossRef] [PubMed]

1974 (1)

R. F. Quick, “A vector magnitude model of contrast detection,” Kybernetik 16, 65–67 (1974).
[CrossRef]

1970 (1)

1969 (1)

F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
[PubMed]

1968 (1)

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

1967 (2)

D. P. Andrews, “Perception of contour orientation in the central fovea. Part I: Short lines,” Vision Res. 7, 975–997 (1967).
[CrossRef] [PubMed]

R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).

Abramov, I.

R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).

Albrecht, D. G.

R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
[CrossRef]

Andrews, D. P.

D. P. Andrews, “Perception of contour orientation in the central fovea. Part I: Short lines,” Vision Res. 7, 975–997 (1967).
[CrossRef] [PubMed]

Beverley, K. I.

D. Regan, K. I. Beverley, “Postadaptation orientation discrimination,” J. Opt. Soc. Am. A 2, 147–155 (1985).
[CrossRef] [PubMed]

D. Regan, K. I. Beverley, “Spatial-frequency discrimination and detection: comparison of postadaptation thresholds,” J. Opt. Soc. Am. A 73, 1684–1690 (1984).

Boynton, R. M.

R. M. Boynton, Human Color Vision (Holt, Rinehart, and Winston, New York, 1979).

Bradley, A.

A. Bradley, B. C. Skottun, “The effects of large orientation and spatial frequency differences on spatial discriminations,” Vision Res. 24, 1889–1896 (1984).
[CrossRef] [PubMed]

Burbeck, C. A.

Campbell, F. W.

F. W. Campbell, J. Nachmias, J. Jukes, “Spatial-frequency discrimination in human vision,” J. Opt. Soc. Am. 60, 555–559 (1970).
[CrossRef] [PubMed]

F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
[PubMed]

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

Cleland, B. G.

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

Cohn, T. E.

T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
[CrossRef] [PubMed]

Cooper, G. F.

F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
[PubMed]

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

Dean, A.

D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
[CrossRef] [PubMed]

A. Dean, “The variability of discharge of simple cells in the cat striate cortex,” Exp. Brain Res. 44, 437–440 (1981).
[CrossRef] [PubMed]

DeValois, R. L.

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

R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
[CrossRef]

R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).

Enroth-Cugell, C.

F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
[PubMed]

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

Freeman, R. D.

B. C. Skottun, R. D. Freeman, “Stimulus specificity of binocular cells in the cat’s visual cortex: ocular dominance and the matching of left and right eyes,” Exp. Brain Res. 56, 206–216 (1984).
[CrossRef]

Gelb, D. J.

Green, D. G.

T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
[CrossRef] [PubMed]

Green, D. M.

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

Hepler, N.

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

Hirsch, J.

Howard, I. P.

I. P. Howard, Human Visual Orientation (Wiley, Chichester, England, 1982).

Hylton, R.

Jukes, J.

Kimura, M.

K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
[PubMed]

K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
[PubMed]

Mead, W. R.

R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).

Movshon, J. A.

D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
[CrossRef] [PubMed]

D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
[PubMed]

Nachmias, J.

Orban, G. A.

E. Vandenbussche, G. A. Orban, “Meridional variations in the line orientation discrimination of the cat,” Behavior Brain Res. 9, 237–255 (1983).
[CrossRef]

Quick, R. F.

R. F. Quick, “A vector magnitude model of contrast detection,” Kybernetik 16, 65–67 (1974).
[CrossRef]

Regan, D.

Skottun, B. C.

A. Bradley, B. C. Skottun, “The effects of large orientation and spatial frequency differences on spatial discriminations,” Vision Res. 24, 1889–1896 (1984).
[CrossRef] [PubMed]

B. C. Skottun, R. D. Freeman, “Stimulus specificity of binocular cells in the cat’s visual cortex: ocular dominance and the matching of left and right eyes,” Exp. Brain Res. 56, 206–216 (1984).
[CrossRef]

Swets, J. A.

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

Tanaka, K.

K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
[PubMed]

K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
[PubMed]

Tanner, W. P.

T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
[CrossRef] [PubMed]

Thompson, I. D.

D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
[PubMed]

Thorell, L. G.

R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
[CrossRef]

Tolhurst, D. J.

D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
[CrossRef] [PubMed]

D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
[PubMed]

Toyama, K.

K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
[PubMed]

K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
[PubMed]

Vandenbussche, E.

E. Vandenbussche, G. A. Orban, “Meridional variations in the line orientation discrimination of the cat,” Behavior Brain Res. 9, 237–255 (1983).
[CrossRef]

Westheimer, G.

G. Westheimer, “Visual hyperacuity,” Prog. Sensory Physiol. 1, 1–30 (1981).
[CrossRef]

Wilson, H. R.

Yund, E. W.

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

Behavior Brain Res. (1)

E. Vandenbussche, G. A. Orban, “Meridional variations in the line orientation discrimination of the cat,” Behavior Brain Res. 9, 237–255 (1983).
[CrossRef]

Exp. Brain Res. (3)

B. C. Skottun, R. D. Freeman, “Stimulus specificity of binocular cells in the cat’s visual cortex: ocular dominance and the matching of left and right eyes,” Exp. Brain Res. 56, 206–216 (1984).
[CrossRef]

A. Dean, “The variability of discharge of simple cells in the cat striate cortex,” Exp. Brain Res. 44, 437–440 (1981).
[CrossRef] [PubMed]

D. J. Tolhurst, J. A. Movshon, I. D. Thompson, “The dependence of response amplitude and variance of cat visual cortical neurones on stimulus contrast,” Exp. Brain Res. 41, 414–419 (1981).
[PubMed]

J. Gen. Physiol. (1)

T. E. Cohn, D. G. Green, W. P. Tanner, “Receiver operating characteristic analysis. Application to the study of quantum fluctuations in optic nerve of Rana pipiens,” J. Gen. Physiol. 66, 583–616 (1975).
[CrossRef] [PubMed]

J. Neurophysiol. (3)

R. L. DeValois, I. Abramov, W. R. Mead, “Single cell analysis of wavelength discrimination at the lateral geniculate nucleus in the macaque,” J. Neurophysiol. 30, 415–433 (1967).

K. Toyama, M. Kimura, K. Tanaka, “Cross-correlation analysis of interneuronal connectivity in cat visual cortex,” J. Neurophysiol. 46, 191–201 (1981).
[PubMed]

K. Toyama, M. Kimura, K. Tanaka, “Organization of cat visual cortex as investigated by cross-correlation technique,” J. Neurophysiol. 46, 202–214 (1981).
[PubMed]

J. Opt. Soc. Am. (3)

J. Opt. Soc. Am. A (4)

J. Physiol. (2)

F. W. Campbell, B. G. Cleland, G. F. Cooper, C. Enroth-Cugell, “The angular selectivity of visual cortical cells to moving gratings,” J. Physiol. 198, 237–250 (1968).
[PubMed]

F. W. Campbell, G. F. Cooper, C. Enroth-Cugell, “The spatial selectivity of visual cells of the cat,” J. Physiol. 203, 223–235 (1969).
[PubMed]

Kybernetik (1)

R. F. Quick, “A vector magnitude model of contrast detection,” Kybernetik 16, 65–67 (1974).
[CrossRef]

Prog. Sensory Physiol. (1)

G. Westheimer, “Visual hyperacuity,” Prog. Sensory Physiol. 1, 1–30 (1981).
[CrossRef]

Vision Res. (5)

D. J. Tolhurst, J. A. Movshon, A. Dean, “The statistical reliability of signals in single neurons in cat and monkey visual cortex,” Vision Res. 23, 775–785 (1983).
[CrossRef] [PubMed]

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

R. L. DeValois, D. G. Albrecht, L. G. Thorell, “Spatial frequency selectivity of cells in macaque visual cortex,” Vision Res. 22, 545–559 (1982).
[CrossRef]

A. Bradley, B. C. Skottun, “The effects of large orientation and spatial frequency differences on spatial discriminations,” Vision Res. 24, 1889–1896 (1984).
[CrossRef] [PubMed]

D. P. Andrews, “Perception of contour orientation in the central fovea. Part I: Short lines,” Vision Res. 7, 975–997 (1967).
[CrossRef] [PubMed]

Other (3)

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

R. M. Boynton, Human Color Vision (Holt, Rinehart, and Winston, New York, 1979).

I. P. Howard, Human Visual Orientation (Wiley, Chichester, England, 1982).

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Figures (1)

Fig. 1
Fig. 1

Data are shown for two simple cells that provided the most reliable response changes to small orientation (A and C) and spatial-frequency (B and D) changes. A and B show orientation and spatial-frequency tuning functions (mean response versus orientation or spatial frequency), respectively. Filled symbols show data from the detailed half-tuning function experiments that provided data for the ROC analysis. Open symbols show data from the preliminary quantitative experiment (only data from the slope that was not studied in detail are shown). Open arrows indicate spontaneous activity level. Vertical bars represent ±2 standard errors. C and D show neurometric functions for the data in A and B, respectively. Each datum represents the result of an ROC analysis of response distributions associated with two different stimuli. Each function gives the estimated probability of correct discrimination as a function of orientation (C) and spatial-frequency (D) difference. Each cell was studied at its optimal temporal frequency: orientation and spatial-frequency data were obtained with gratings drifted at 1 and 4 Hz, respectively.

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