Inhibiroty effects in the detection of 1 cpd jo targets superimposed to angular frequency stimuli or sinewave gratings

Independence among channels processing different aspects of spatial information, including orthogonal stimuli, has beens generally assumed in the literature. We tested independence between the processing of j(o) targets and the processing of either vertical sinosoidal gratings or angular frequency stimuli with suprathreshold summation. We found the detection of a j(o) target at 1 cpd to be affected in an inhibitory fashion by either background angular frequencies in the range of 3-96 cycles or sinewave gratings in the range of 0.8-3.0 cpd. These results demonstrate interactions both among orthogonal stimuli and among channels processing vertical sinewave gratings and j(o) target stimuli. Our discussion focuses on the hypothesis of frequency decomposition in polar coordinates.

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 sinewave 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 equipement to allow comparison 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 given angular frequency filter