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Zoe Kourtzi, Argiro Vatakis, Bart Krekelberg; Global motion from form in the human visual cortex. Journal of Vision 2005;5(8):1063. doi: 10.1167/5.8.1063.
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© ARVO (1962-2015); The Authors (2016-present)
Implied motion, that is the perception of motion in static images that contain no real motion, demonstrates an interesting interaction between motion and form information that are often assumed to be processed along largely separate pathways. Previous neurophysiological studies have shown that areas MT and MST are involved in implied motion perception. The aim of this study was to investigate whether implied motion processing in the human brain is confined to the motion pathway or entails interactions between motion and form areas. We used dynamic Glass patterns that contain no coherent motion. In these patterns motion is implied by the alignment of oriented dot pairs along a common trajectory. We used an event-related fMRI adaptation paradigm, in which decreased responses after repeated presentation of a stimulus compared to stronger responses (rebound) after a change in a stimulus dimension indicate sensitivity of the measured neural populations to the changed dimension. We observed sensitivity for changes in the global structure of Glass patterns in hMT+/V5, consistent with the previous neurophysiological studies. That is, stronger fMRI responses were observed when two different Glass patterns were presented in a trial (e.g. concentric followed by radial) than when the same pattern was presented repeatedly. Similar rebound effects were observed for real-motion patterns. These rebound effects for Glass and real-motion patterns were observed in motion areas V3, V3a and KO, but also the Lateral Occipital Complex (LOC), that is implicated in form analysis. Interestingly, adaptation effects were observed in motion areas when a Glass pattern was followed by a real motion pattern of similar global structure, suggesting that overlapping neural subpopulations encode real and implied motion patterns. In sum, our findings implicate both motion and form areas in the processing of global motion from form.
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