Summary
Responses of visual cortex (area 17) neurons to moving oriented stimuli were recorded from anesthetized cats. The variance of response (SD2) to repeated identical stimuli was directly proportional to response magnitude (R), (SD2 =C2R). The values of C were not found to differ significantly between different types of cortical cells. The relationship predicts that the coefficient of variation (SD/R) will be smallest near the peak of the tuning curve, indicating that the peak response is most reliable for detecting an orientation but not necessarily the most sensitive to a change in orientation. Tuning curves and response variability were then examined to determine the orientation at which the neuron was most sensitive to changes in stimulus orientation using signal detection theory. The discrimination index (d′ = [R1-R2J/SD) for a 1 degree change in stimulus orientation was greatest along the flanks of the tuning curve. In order to generalize the experimental data, response distributions derived from a model of cells with parameters based on experimental data were examined to determine the minimal discriminable change in stimulus orientation. Changes of stimulus orientation between 0.6 and 5 deg of arc could be detected from single responses of a single cell by an optimal observer with 75% accuracy if the orientation change was centered at the most sensitive part of the tuning curve.
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References
Albright TD (1984) Direction and orientation selectivity of neurons in visual area MT of the macaque. J Neurophysiol 32: 1106–1130
Andrews DP (1967) Perception of contour orientation in the central fovea, I. Short lines. Vision Res. 7: 975–997
Bradley A, Skottun BC (1984) The effects of large orientation and spatial frequency differences on spatial discriminations. Vision Res 24: 1889–1896
Bradley A, Skottun BC, Ohzawa I, Sclar G, Freeman RD (1987) Visual orientation and spatial frequency discrimination: a comparison of single neurons and behavior. J Neurophysiol 57: 755–772
Campbell FW, Cleland BG, Cooper GF, Enroth-Cugell C (1968) The angular selectivity of visual cortical cells to moving gratings. J Physiol 198: 237–250
Dean AF (1981) The variability of discharge of simple cells in the cat striate cortex. Exp Brain Res 44: 437–440
De Valois RL, Yund EW, Hepler N (1982) The orientation and directional selectivity of cells in macaque visual cortex. Vision Res 22: 531–544
Gabor AJ, Scobey RP, Wehrli C (1979) Relationship of epileptogenicity to cortical organization. J Neurophysiol 42: 1609–1625
Gilbert CD (1977) Laminar differences in redeceptive field properties of cells in cat primary visual cortex. J Physiol 268: 391–421
Green DM, Swets JA (1966) Signal detection theory and psychophysics. John Wiley and Sons, New York
Hammond P, Mackay D (1977) Differential responses of cat visual cortical cells to textured stimuli. Exp Brain Res 30: 275–296
Heggelund P, Albus K (1978) Response variability and orientation discrimination of single cells in striate cortex of cat. Exp Brain Res 32: 197–211
Henry GH, Bishop PO, Tupper RM, Dreher B (1973) Orientation specificity and response variability of cells in the striate cortex. Vision Res 13: 1771–1779
Henry GH, Dreher B, Bishop PO (1974) Orientation specificity of cells in cat striate cortex. J Neurophysiol 37: 1394–1409
Hubel DH, Wiesel TN (1962) Receptive fields, binocular interaction and functional architecture in the cat's visual cortex. J Physiol 160: 106–154
Movshon JA, Thompson ID, Tolhurst DJ (1978) Spatial and temporal contrast sensitivity of neurones in areas 17 and 18 of the cat's visual cortex. J Physiol 283: 101–120
Rose D (1979) An analysis of the variability of unit activity in the cat's visual cortex. Exp Brain Res 37: 595–604
Rose D, Blakemore C (1974) An analysis of orientation selectivity in the cat's visualcortex. Exp Brain Res 20: 1–17
Schiller PH, Finlay BL, Volman SF (1976) Short-term response variability of monkey striate neurons. Brain Res 105: 347–349
Schiller PH, Finlay BL, Volman SF (1976) Quantitative studies of single-cell properties of monkey striate cortex. II. Orientation specificity and ocular dominance. J Neurophysiol 39: 1320–1333
Sclar G, Freeman RD (1982) Orientation selectivity in the cat's striate cortex is invarient with stimulus contrast. Exp Brain Res 46: 457–461
Skottun BC, Bradley A, Sclar A, Ohzawa I, Freeman RD (1987) The effects of contrast on visual orientation and spatial frequency discrimination: a comparison of single cells and behavior. J Neurophysiol 57: 773–786
Tolhurst DJ, Movshon JA, Dean AF (1981) The dependence of response amplitude and variance of cat visual cortical neurons on stimulus contrast. Exp Brain Res 41: 414–419
Tolhurst DJ, Movshon JA, Dean AF (1983) The statistical reliability of signals in single neurons in cat and monkey visual cortex. Vision Res 23: 775–785
Tomko GJ, Crapper DR (1974) Neuronal variability: nonstationary responses to identical stimuli. Brain Res 79: 405–418
van Kan PLE, Scobey RP, Gabor AJ (1985) Response covariance in cat visual cortex. Exp Brain Res 60: 559–563
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Scobey, R.P., Gabor, A.J. Orientation discrimination sensitivity of single units in cat primary visual cortex. Exp Brain Res 77, 398–406 (1989). https://doi.org/10.1007/BF00274997
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DOI: https://doi.org/10.1007/BF00274997