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Nicole Streeb, Xin Chen, Jay Hegdé; Learning-Dependent Changes in Brain Responses While Learning to Break Camouflage: A Human fMRI Study. Journal of Vision 2012;12(9):1131. doi: 10.1167/12.9.1131.
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Camouflage represents an extreme case of figure-ground segregation whereby a target object, even when in ‘plain view’, is difficult to distinguish from its background. Neural mechanisms by which we recognize a camouflaged object, i.e., break its camouflage, are largely unclear. To characterize the neural responses underlying camouflage-breaking, we carried out two human fMRI experiments. The first experiment used a rapid, event-related design in which subjects had to detect a novel ‘digital embryo’ target camouflaged against a background of a large number of distractor digital embryos (Hegdé et al, JOV 6:677, 2006). We found that the responses in many regions of interest (ROIs), most notably fusiform gyrus (FG) and superior temporal suclus (STS) were significantly larger during those trials in which the subjects (N = 13) correctly reported the presence or absence of a target, compared to the responses during incorrect trials (p <0.05, corrected for multiple comparisons). To assess the extent to which the response patterns are independent of the experimental conditions, we carried out a second experiment using a time-resolved design and stimuli in which the target was a human face camouflaged against uniform background texture. The response patterns of many brain regions, including FG and STS, were similar to those in the first experiment, indicating that the responses were not idiosyncratic to the category of the target object or the nature of the background. On other hand, the BOLD responses in the intraparietal sulcus (IPS) were suppressed below baseline levels during behaviorally correct trials in the second experiment, while the corresponding responses were enhanced above baseline levels in the second experiment. Together, these results suggest, although do not prove, that camouflage-breaking may involve a ‘core’ set of brain regions that whose responses are largely invariant to the nature of the target and of the background.
Meeting abstract presented at VSS 2012
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