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  • D H Kelly
  • 1979
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)
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)
  • D H Kelly
  • 1983
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)
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)
  • D H Kelly
  • 1981
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)