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Melanie Palomares, Anthony Norcia, Alex Wade, Mark Pettet, Vladimir Vildavski, Greg Appelbaum; On the differences and similarities between real and implied motion: a high-density EEG study. Journal of Vision 2007;7(15):93. doi: https://doi.org/10.1167/7.15.93.
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© ARVO (1962-2015); The Authors (2016-present)
When Glass patterns (Glass, 1969) are sequentially presented at a rapid rate, they evoke a strong percept of coherent motion that is often mistaken for real motion (Ross et al., 2004). These “dynamic” Glass patterns (dGPs) have little coherent motion energy and the corresponding motion percept has been referred to as being “implicit”. In this study, we compared and contrasted the cortical mechanisms involved in dGP and real motion processing by recording whole-head visual evoked potentials (VEPs). Using a cortically constrained minimum norm inverse technique, we determined the source distribution temporal sequence of cortical activations in a set of Regions of Interest (ROIs) determined by fMRI. These ROIs comprised either retinotopically or functionally defined areas, including hMT+. We found that both dGPs and real motion activated common areas of occipital, dorsal, temporal and frontal regions of cortex. However, the temporal poles are more activated by dGps than real motion. Moreover, real motion is processed faster than dGps, particularly in hMT+ and V4. Since dGps elicit responses in cortical areas associated with motion processing, these common areas may account for the sense of implicit motion. However, the stronger Glass pattern activity in areas such as AIT, which lies at the top of the ventral pathway, may be more associated with the form of the Glass pattern rather than its motion.
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