Exploring the spatiotemporal properties of fractal rotation perception

Abstract

A series of three experiments was conducted with the aim of determining the processing nature of the fractal rotation stimulus introduced by C. P. Benton, J. M. O'Brien, and W. Curran (2007). This stimulus has been proposed to be invisible to first-order sensitive mechanisms considering it is drift-balanced. Rather, motion perception would require the analysis of spatial structure (orientation) changing over time. In Experiment 1, spatiotemporal properties of fractal rotation perception have been explored, in comparison with first-order rotation perception. In Experiment 2, a motion paradigm similar to the one developed by K. Nakayama and C. W. Tyler (1981) and later used by A. E. Seiffert and P. Cavanagh (1998) has been used to characterize the motion processing mechanism responsible for fractal rotation perception. In Experiment 3, we have used a paradigm similar to N. E. Scott-Samuel and A. T. Smith (2000) to evaluate whether fractal rotation perception is analyzed by common or distinct mechanisms to those for first-order rotation perception. Results indicate that fractal rotation perception involves feature-tracking processes with mechanisms responding to global orientation-based changes of the image. Given the absence of cancellation of first-order and fractal rotation motion signals, we can therefore conclude that the first-order and fractal motion sensitive pathways are dissociable at early stages of the visual processing stream.

Relationship between Fractal Dimension and Spectral Scaling Decay Rate in Computer-Generated Fractals

“…An example would be a fractal pattern that undergoes fractal change over time. Responses to dynamic stimuli have a long history of consideration in vision research that continues today [50,51], though few have focused on perception of fractal motion [52,53]. Equation (11) provides the scaffolding to extend perceptual research into the study of dynamic fractals.…”

Feature tracking and aging

“…To avoid these two potential issues, the current study used a second-order motion stimulus proven to be processed by a high-level feature tracking motion system (Lagacé-Nadon et al, 2009), namely fractal rotation. This stimulus was originally introduced by Benton et al (2007).…”

“…This stimulus was originally introduced by Benton et al (2007). We modified the stimulus (Lagacé-Nadon et al, 2009) to eliminate all high spatial frequency components from its composition. It is composed of successive noise frames rich in orientation cues changing over time resulting in a rotating percept (Figure 1).…”

“…Indeed, to perceive rotation from fractal stimuli, one needs to track changes in orientation over time, rather than local luminance translations. As a result, fractal rotation is processed by the high-order feature tracking motion system (Lagacé-Nadon et al, 2009). We therefore chose fractal rotation as our second-order motion stimulus because (1) it is robustly “invisible” to the first-order motion system and, (2) it can be composed exclusively of low spatial frequencies, which are not or little affected by aging (Owsley et al, 1983), thereby minimizing visibility difference between younger and older adults.…”

“…Consequently, some age-related sensitivity loss to second-order motion could be due to a lower sensitivity to the texture rather than to motion processing per se . To avoid these two potential issues, we used a second-order motion stimulus void of high spatial frequencies and which has been shown to be processed by a high-level feature tracking motion system, namely fractal rotation (Lagacé-Nadon et al, 2009). We found an age-related deficit on second-order motion processing at all temporal frequencies including the ones for which no age-related effect on first-order motion processing was observed.…”