Detection of periodic motion trajectories: Effects of frequency and radius

Abstract

Periodic trajectories are an important component of biological motion. Or, Thabet, Wilkinson, and Wilson (2011) studied radial frequency (RF) motion trajectory detection and concluded that, for RF2-5 trajectories, the threshold function paralleled that of static RF patterns. We have extended Or et al.'s (2011) findings to a broader range of RFs (three to 24 cycles) and across a 4-fold range of radii (1°-4°). We report that (a) thresholds for RF trajectories decrease as a power function of RF for low RF trajectories (three to six cycles) before approaching an asymptote at high RFs (12-24 cycles); (b) detection thresholds for RF trajectories scale proportionally with radius; and (c) there is no lower versus upper field advantage in the parafoveal field for stimuli displaced from fixation on the vertical midline. The results are compared to earlier findings for static RF thresholds, and we argue that our findings support the existence of parallel spatial and temporal processing channels that may contribute to both action perception and production.

The effect of spatiotemporal displacement on the integration of shape information

“…Therefore, it is unclear how the information is being processed early in the visual stream, but our results do suggest that integration of this motion-defined information occurs in the same manner as for contour-defined information. Perhaps, as suggested by Wilkinson et al (2016), the motion RFs are providing a signal to higher levels of the ventral visual stream resulting in the similarity of results found between contour-defined RF patterns and motiondefined RF patterns found in the current study and by Wilkinson et al (2016).…”

“…Recent work has shown a number of similarities between motion RFs and static RF patterns (Wilkinson et al, 2016). They found that thresholds increase proportional to the pattern's radius and thresholds decrease as a function of increasing RF number, which conforms to a power-law relationship, both of which have been shown for static RF patterns (Wilkinson et al, 1998).…”

“…Previous behavioural studies support this hypothesis as the processing of motion RF patterns (Daar, Or, & Wilson, 2012;Or et al, 2011;Wilkinson, Haque, Or, Gottlieb, & Wilson, 2016;Wilson & Fung, 2016) show a similar pattern of results compared to static RF patterns when changing parameters such as radius, frequency, and cycles of modulation (Bell, Wilkinson, Wilson, Loffler, & Badcock, 2009;Loffler et al, 2003;Wilkinson et al, 1998). Furthermore, Gorbet et al (2012) compared the results of motion RF patterns with those obtained with open motion patterns (a sinusoidally modulated line pattern revealed by a dot with a DOG profile, tracing either two or three cycles).…”

“…Therefore, we considered a possibility suggested by Gorbet et al (2014), in which ''motion streaks'' (Geisler, 1999) produce form information that is combined using the same mechanisms as those that underpin processing of contour-defined patterns. However, Wilkinson et al (2016) provide evidence against this explanation, as they found no effect on observer thresholds when they changed the duration of presentation (i.e., the average speed of motion) or contrast of the dot used for their motion RF stimulus, both of which were designed to change the length of motion streaks. Therefore, it is unclear how the information is being processed early in the visual stream, but our results do suggest that integration of this motion-defined information occurs in the same manner as for contour-defined information.…”

Integration of shape information occurs around closed contours but not across them

“…The results of Rossit et al are consistent with the idea that action and perceptual pathways are different (Goodale & Milner, 1991;Goodale & Milner, 1992;Milner & Goodale, 2008) and, therefore, may have differing visual field biases (Danckert & Goodale, 2003). Additional evidence also comes from Wilkinson, Haque, Or, Gottlieb, and Wilson (2016), who also find no difference in sensitivity to motion-defined RF patterns when presented in either the upper or lower visual field. Although these patterns are defined by motion, the pattern of results for changes in frequency, radius, and cycles of modulation are highly similar to static RF patterns.…”