The aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/360º defined in polar coordinates. We measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. The results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360º) filters surrounded on both sides by strong inhibition. These results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.
Visual processing of form; angular frequency; narrow-band frequency filters; supra-threshold summation method
