Energy model for contrast detection: spatiotemporal characteristics of threshold vision |
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Authors: | V Manahilov W Simpson |
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Institution: | (1) Institute of Physiology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 23, 1113 Sofia, Bulgaria, BG;(2) Department of Vision Sciences, Glasgow Caledonian University, City Campus, Cowcaddens Road, Glasgow G4 0BA, UK, GB |
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Abstract: | A model for contrast detection of spatiotemporal stimuli is proposed which consists of a spatiotemporal linear filter, an
energy device and a threshold device. Assuming the existence of independent intrinsic noise, the probability of stimulus detection
was approximated by a Weibull function of the response energy. With this assumption, the stimulus energy is a constant at
fixed detection probability. This energy model for contrast detection satisfactorily accounted for the elliptical threshold
contours of line pairs at stimulus separations within the range 2–30 min and at stimulus onset asynchronies within the range
20–140 ms. The threshold contour at a large stimulus onset asynchrony (300 ms) was in the form of a rounded square. This finding
was explained by assuming that the probability of seeing the line pair was determined by the joint probability that at least
one stimulus had been detected. With the energy model, the temporal and spatial autocorrelation functions of the response
to a flashed line were evaluated. The autocorrelation functions thus determined were used to predict the temporal contrast
sensitivity function to a flickering line stimulus and the spatial contrast sensitivity function to flashed gratings, which
were in agreement with the experimental data. The data obtained were fitted adequately by an impulse response approximated
by a spatiotemporal Gabor-like function.
Received: 08 December 1997 / Accepted in revised form: 26 January 1999 |
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