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The stabilized contrast-sensitivity function measured at a constant retinal velocity is tuned to a particular spatial frequency, which is inversely related to the velocity chosen. The Fourier transforms of these constant-velocity passbands have the same form as retinal receptive fields of various sizes. At low velocities, in the range of the natural drift(More)
Moving the retinal image of a sinusoidal grating at a constant velocity (compensated for eye movements) provides controlled spatial and temporal frequencies at every point in the stimulus field. Using this controlled-velocity technique, we have measured the detection threshold for isoluminance, red/green gratings as a function of their spatial and temporal(More)
Spatiotemporal sine-wave contrast thresholds were measured at four retinal eccentricities: 0 degrees, 3 degrees, 6 degrees, and 12 degrees. Threshold functions of spatial frequency were determined for each eccentricity at two selected temporal frequencies, and functions of temporal frequency at two selected spatial frequencies. Fixation was controlled by(More)
We measure threshold for a vertical test grating superimposed on a fixed-contrast horizontal background grating of the same spatial and temporal frequency. The rate of change of this threshold with increasing contrast of the background grating is a measure of the contrast gain of the responding mechanism. Large slopes (high contrast gains) occur when(More)
Several types of measurement were made of the negative afterimages formed by viewing chromatic and achromatic sine-wave conditioning gratings that were stabilized on the retina. We varied the spatial frequency, contrast, and duration of the conditioning stimulus and the interval between its offset and the afterimage measurement. Different methods of(More)
Spatial frequency and orientation selectively, the most prominent properties of image-processing in the striate cortex, are not uniform throughout the spatiotemporal frequency domain. Some current models include one "transient" mechanism at very high velocities (i.e. low spatial and high temporal frequencies), and multiple "sustained" mechanisms elsewhere(More)
The stabilized spatiotemporal threshold response surface can be modeled as the linear difference between the threshold response surfaces of two mechanisms, each of which is simply the product of a spatial and temporal frequency response curve. With no free parameters, the resulting model is shown to be a good fit to available data.
To demonstrate that eye movements have profound effects on the sine-wave contrast threshold, the author uses a new method of stabilizing the retinal image, in which the Purkinje reflections from the eye move the stimulus pattern displayed on a CRT screen. Calibration of this compensatory motion is very critical; a gain error greater than 1% may produce(More)
Over a range of high temporal and low spatial frequencies, counterphase flickering gratings evoke the so-called frequency-doubling illusion, in which the apparent brightness of the grating varies at twice its real spatial frequency. The form of the nonlinearity that causes this second-harmonic distortion of the visual response was determined by a(More)