Antagonism between fine and coarse motion sensors depends on stimulus size and contrast

Abstract

The perceived direction of motion of a brief visual stimulus that contains fine features reverses if static coarser features are added to it. Here we show that the reversal in perceived direction disappears if the stimulus is reduced in size from 2.8 deg to 0.35 deg radius. We show that for a stimulus with 1.4 deg radius, the reversals occur when the ratio between the contrast of the fine features and of the coarser features is higher than 0.8 and lower than 4. For stimulus with 0.35 deg radius, the reversals never appear for any contrast ratio. We also show that if the stimulus is presented within an annular window with small radius, errors disappear but they return if the radius is increased to 2 deg. The errors in motion discrimination described here can be explained by a model of motion sensing in which the signals from fine-scale and coarse-scale sensors are subtracted from one another (I. Serrano-Pedraza, P. Goddard, & A. M. Derrington, 2007). The model produces errors in direction when the signals in the fine and coarse sensors are approximately balanced. The errors disappear when stimulus size is reduced because the reduction in size differentially reduces the response of the low spatial frequency motion sensors.

Comparing the effect of the interaction between fine and coarse scales and surround suppression on motion discrimination

“…These results are in the same direction as previous results (Serrano-Pedraza et al, 2007;Serrano-Pedraza & Derrington, 2010). In effect, previous results have shown that the percentage of errors in direction discrimination increased with increasing size (Serrano-Pedraza & Derrington, 2010).…”

“…For the first time, we have measured duration thresholds for complex stimuli composed of fine and coarse scales. The duration-threshold measurements allowed us to characterize in stimulus terms a phenomenon that has been reported in performance terms in previous studies (Derrington & Henning, 1987;Henning & Derrington, 1988;Derrington et al, 1993;Serrano-Pedraza et al, 2007;Serrano-Pedraza & Derrington, 2010). In those studies, the authors fixed the presentation durations of the complex stimulus and measured the proportion of correct responses for direction discrimination as a function of the duration.…”

“…There is another counterintuitive psychophysical result in motion perception that shows that motion discrimination at short durations is impaired when the size of a complex stimulus that consists of a moving fine-scale (high-spatial-frequency) pattern added to a static coarse-scale (low-spatial-frequency) pattern increases (Derrington & Henning, 1987;Henning & Derrington, 1988;Derrington, Fine, & Henning, 1993;Serrano-Pedraza, Goddard, & Derrington, 2007;Serrano-Pedraza & Derrington, 2010; see the ''Interaction across different spatial scales'' section in Nishida, 2011). Although previous results are consistent with the idea that early processing by the human visual system analyses fine-scale and coarse-scale image features separately using motion sensors that are selective for spatial frequency and have localized receptive fields (S. J.…”

Paradoxical Psychometric Functions (“Swan Functions”) are Explained by Dilution Masking in Four Stimulus Dimensions

“…Are the results of Serrano-Pedraza and Derrington (2010) related to ours? The model they propose takes the MAX response across noiseless and mutually suppressive mechanisms sensitive to different spatial frequencies.…”

“…Serrano-Pedraza and Derrington (2010) judged perceived direction of motion for a 3 c/deg Gabor target moving at 4 deg/sec, superimposed on a static 1 c/deg Gabor mask. When the stimulus was quite large (3.3° full width at half-height [FWHH]), the psychometric function relating target contrast to proportion of correct direction judgements was steep and nonmonotonic, with a similar form to those in Figure 3.…”