Visual contrast perception in human beings: psychophysical evidence for high angular frequency channels / Percepção visual de contraste em humanos: evidência psicofísica para canais de freqüência angular alta

Abstract

The aim of this study was to measure narrow-band frequency response curves for four angular frequency filters. The test frequencies were 32, 48, 64 and 96 cycles/360º. Six humans observers with normal or corrected visual acuity measured nine curves for each filter, with a supra-threshold response summation psychophysical method allied with a forced-choice method. The results showed maximum summation effects at test frequency for filter frequencies 32, 48, 64 and 96 cycles/360º, as well as a strong inhibition for neighboring frequencies. These results are consistent with the existence of narrow-band angular frequency filters in the human visual system either through summation or the inhibition of specific high angular frequency ranges.

Keywords

• Visual perception of form
• angular frequency filter
• angular frequency
• supra-threshold summation method