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Deborah Apthorp, Bahador Bahrami, Christian Kaul, D. Samuel Schwarzkopf, David Alais, Geraint Rees; The neural correlates of motion streaks: an fMRI study. Journal of Vision 2010;10(7):844. doi: 10.1167/10.7.844.
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© ARVO (1962-2015); The Authors (2016-present)
Aim: Due to temporal integration in the visual system, a fast-moving object can generate a static, oriented trace (a ‘motion streak’). These are generally not seen, but might be used to judge direction of motion more accurately (Geisler, 1999). Psychophysics and single-unit studies support this hypothesis, but no physiological evidence from the human brain has yet been provided. Here we use functional magnetic resonance imaging combined with standard univariate as well as multivariate pattern classification techniques to investigate the neural correlates of motion streaks. Method: Observers viewed fast (‘streaky’) or slow-moving dot fields, moving at either 45 or 135 degrees, or static, oriented patterns (filtered noise) at the same orientations, while performing a fixation task in the scanner (3T, high-res sequence, 1.5 x 1.5 x 1.5mm, 32 slices, TR= 3.2s). 10 sessions, each with 6 blocks per session (randomized block design) gave 10 blocks for each stimulus type. Results: Initial univariate group analysis in SPM5 showed greater activation in early cortical areas (V1, V2 and V3) when comparing fast to slow motion, but no increased activation in V5/MT+; the pattern of activity was similar to that seen when comparing static, oriented conditions to fixation rest. A multivariate pattern classifier trained on brain activity evoked by static, oriented patterns could successfully generalize to decoding brain activity evoked by fast but not slow motion sessions. These results suggest that static, oriented “streak” information is indeed present in human early visual cortex when viewing fast motion.
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