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Jeremy Fesi, Michael Yannes, Rick Gilmore; Temporal modulations of motion properties produce distinct motion-contrast and form-related VEP responses in adults and infants. Journal of Vision 2009;9(8):669. doi: 10.1167/9.8.669.
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© ARVO (1962-2015); The Authors (2016-present)
Motion information contributes to the separation of figure from background, and yet relatively little is known about the neural circuitry or developmental time course of this aspect visual processing. We measured steady-state visual evoked potential (SSVEP) responses to moving dot displays in which four “figure” regions emerged from and disappeared into the background at a specific frequency (1.2 Hz: 1F1), based on differences in dot direction, speed, motion coherence, density, and lifetime. We previously reported that in adults, responses at the fundamental frequency (1F1) increased monotonically with direction, coherence, and speed, while responses at twice the fundamental (2F1) increased at low levels before saturating. Here, we report that adults' 2F1 responses increase then saturate at relatively short dot lifetimes (111 ms), and that responses are strong, but consistent across a wide range (2–24%) of global dot densities. Further, in infants unlike adults, 1F1 responses to direction differences show an inverted-U shaped pattern, with peaks at intermediate direction differences (45–90 deg), and weak responses to 180 deg. We conclude that mechanisms underlying the detection of motion contrast and 2D form-from-motion in adults operate relatively quickly and are robust under sparse signal conditions. Infants show larger individual differences than adults, and in some cases, non-monotonic responses to motion contrast. This suggests that some aspects of motion contrast and 2D form-from-motion processing mature early, while others do not. High-density SSVEP data from both infants are adults are beginning to identify the cortical substrates for these perceptual processes.
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