Bandwidth of Visual Filters that Transmit the Spatial Frequency Modulation

It is known that scene is divided into diUerent local segments on early stages of visual processing, and every single segment is depicted in parallel independently. On the next stage the local segments are grouped in a certain way. This operation is realized with so-called second-order Vlters. Every Vlter is featured by its bandwidth. Our goal in this study is to determine the bandwidths in three types of parameters of second-order Vlters sensitive to spacial frequency modulation: axis (orientation), frequency and phase of modulation. The study was carried out in backward masking paradigm. Gabor textures with sinusoidal spatial frequency modulation of these elements were used as test stimuli. Patches used in the masking stimuli were also modulated in frequency with diUerent orientation, frequency or phase of modulation compared to test stimulus. Threshold amplitude of modulation in test stimulus was determined in two-alternative forced-choice procedure. The second-order Vlters spatial frequency bandwidth was determined to be about 3 octaves. At the same time we found that Vlters were not selective to orientation and phase of modulation. Selectivity to modulation frequency is assumed to show the receptive Veld organization in which on-center is surrounded by oU-periphery. No orientation selectivity may be an evidence of concentric organization, whereas no phase selectivity indicates receptive Veld nonlinearity.