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Julian Wallace, Nicholas Scott-Samuel, Andy Smith; A cortical locus for high-level motion processing?. Journal of Vision 2007;7(9):780. doi: 10.1167/7.9.780.
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There is good evidence for at least two motion processes: 1) a low-level process based on motion energy, with no reference to spatial structure, and 2) a high-level process based on the changing location of spatial image features or primitives. A number of imaging studies have attempted to identify the cortical location of high-level motion processing. The lack of consensus from these studies may be attributed to the wide variety of stimuli used. We attempted to identify pure high-level motion responses across different stimulus types, and controlled for stimulus flicker. The stimuli were a radial version of the missing-fundamental stimulus (Georgeson & Harris, 1990), and the reverse phi stimulus (Anstis, 1970). With no inter-frame interval (IFI), motion is perceived in the (low-level) energy direction, and at longer IFIs, motion is perceived in the opposite (high-level) features direction. In an event-related stimulation paradigm, these stimuli and corresponding flicker controls were viewed passively (n=12), and functional images were acquired (3T Siemens Scanner at Royal Holloway University of London). The data were analysed using SPM2, and first-level contrasts of individual stimuli against flicker, and motion-type (collapsed across stimuli) versus flicker were then assessed using a second-level random-effects group analysis. The resulting activations were different for low-level and high-level contrasts, and identified a high-level motion specific response in the region of the intra-parietal sulcus (IPS). This area has previously been identified with attention, and the result is therefore consistent with theories that high-level motion processing involves attentional control for ‘feature tracking
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