Abstract
Abstract: :
Purpose: To determine the interaction between spatial and temporal parameters in the contrast sensitivity of pigeons. Methods: Four White Carneaux pigeons were trained to discriminate a sinusoidal grating from a luminance-matched blank in a three-reversal staircase psychophysical procedure in which the contrast was varied according to performance. The spatial frequency for each session was selected randomly from a group of five spatial frequencies ranging from 0.42-1.26 c/deg. Within each session, the temporal frequency varied from 1-32 Hz. Results: When plotted as a function of spatial frequency, the contrast-sensitivity functions peaked in the range 0.7-1.0 c/deg. When compared to data that had been collected at 0 Hz temporal modulation, the temporally modulated spatial contrast-sensitivity functions showed reduced contrast sensitivity, especially at the higher spatial frequencies, and reduced peak spatial frequency. When plotted as a function of temporal frequency, the contrast-sensitivity functions were flat up to 8-16 Hz. Above 16 Hz, the curves showed a sharp roll off. The high temporal frequency cut off, which is roughly equivalent to the critical flicker frequency, was plotted as a function of spatial frequency. The function rose to a peak of 100 Hz at approximately 0.7 c/deg; at higher spatial frequencies, it dropped to approximately 65 Hz and remained flat. When plotted as a three-dimensional, spatiotemporal contrast-sensitivity surface, the data had a number of characteristics in common with the three-dimensional spatiotemporal model of contrast sensitivity proposed by Burbeck and Kelly (1980). Conclusion: Although the pigeon peak spatial and temporal frequencies and peak contrast sensitivity are all lower than in humans, the similarity in the shape of the spatiotemporal contrast-sensitivity function suggests similar processing mechanisms.
Keywords: 586 spatial vision • 596 temporal vision • 316 animal model