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Zygmunt Pizlo, Sungeun Kim, Thomas Talavage, Filip Pizlo, Robert Steinman; Neural substrate of the perception of phi (pure) movement. Journal of Vision 2008;8(6):128. doi: 10.1167/8.6.128.
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© ARVO (1962-2015); The Authors (2016-present)
Recent developments in understanding the distinction between phi (pure apparent movement) and beta (optimal apparent movement), led to what is called “magniphi”, a very vivid phi stimulus (Steinman et al., Vision Research, 2000). With this stimulus in hand it was possible to show that the neural substrates, as well as the perceptions of these different kinds of motion, are different. This was done by using functional magnetic resonance imaging (fMRI) experiment. In this experiment, 18 subjects underwent fMRI at 1.5T (8 subjects, 32 axial slices, TR/TE=3000/40 ms) or 3.0T (10 subjects, 37 axial slices, TR/TE=3000/30 ms). Two white-on-black visual stimuli were used: (i) one dot moving through nine positions around the fixation point, or (ii) eight dots rotating through the same nine positions. Two rates were used: 220 ms/revolution or 40 ms/revolution in clockwise or counterclockwise direction. These conditions were presented with 3 s duration using an event-related paradigm with ISI=15 s and a temporal jitter that was an integer multiple of 3 s. Eight dots shown at high rate lead to magniphi; the remaining three conditions lead to beta motion. Each of the conditions was presented 45 times over the course of 12 runs. Fourteen out of 18 datasets have been processed by using statistical parametric mapping 5 (SPM5) to perform random effect analysis between stimulus conditions and a rest condition. These results were thresholded at pFDR[[lt]]0.05 to identify differential activities favoring magniphi. We found statistically strong bilateral activities in superior colliculus and pulvinar favoring magniphi. There was no difference in activities along the dorsal visual processing stream except in the right MST, bilateral SPL, and bilateral BA6 areas, which were stronger activated by one or more beta stimulus conditions, although this stream was significantly stimulated by both magniphi and beta in general.
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