Inhibitory sidebands in multiple angular frequency filters in the human visual system.
The view of multiple spatial frequency channels to characterize spatial factors determining the processing of contrast and brightness information has been mostly based on studies using sine wave gratings. In a study of angular frequency filtering, we demonstrated the presence of multiple peaks reflecting inhibitory activity in the measurement of a 24-cycle angular frequency filter (Simas MLB & Dodwell PC (1990). Spatial Vision, 5: 59-74). We now report sensitivity functions for angular frequency filters at 2, 4, 9, 13, 16, and 47 cycles, and have included new data for 24 cycles using the same method and analogous equipment to allow comparisons with our previous study. The present findings consistently show inhibitory effects flanking the filter's specific test frequency and, in every case, much weaker or almost no inhibition occurs at the specific test frequency for the given angular frequency filter.