Abstract

Billock and Harding (ARVO, 1991) derived three temporal frequency mechanisms responsible for the independent detection of temporal modulated 4 c/deg gratings. Here we extend this approach to a wide range of spatial frequencies. We measured binocular spatio–temporal contrast sensitivity in thirty young (18–35 yr) observers. The stimuli were presented at 100 cd/m² and were embedded in an extended surround of the same luminance and chromaticity. Spatial frequency ranged from 0.5 to 22.6 c/deg in steps of an octave. Temporal frequency ranged from 0.25 to 32 Hz in steps of 0.5 octave. For each spatial frequency, a temporal frequency contrast sensitivity correlation matrix was computed. These matrices were factor analyzed and solutions for 1–4 factors were varimax-rotated to obtain easily interpretable structures. Our criteria for the discernment of mechanisms were the variance accounted for by each factor and the meaningfulness of the derived tuning. Based on these criteria we found evidence for three broadband temporal frequency mechanisms: (1) a high temporal frequency mechanism with a maximum near 8 Hz and a spatial frequency range of 0.5 to 5.7 c/deg; (2) an intermediate temporal frequency mechanism with a peak near 2 Hz and a spatial frequency range of 0.5 to 4 c/deg; (3) a low temporal frequency mechanism, with a peak between 0 and 0.5 Hz at spatial frequencies > 2 c/deg.

© 1991 Optical Society of America