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Mark J. Fenske, Jasmine Boshyan, Moshe Bar; Can a gun prime a hairbrush? The “initial guesses” that drive top-down contextual facilitation of object recognition. Journal of Vision 2005;5(8):851. doi: 10.1167/5.8.851.
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© ARVO (1962-2015); The Authors (2016-present)
Contextual associations provide predictive information about which visual objects are likely to appear together. How does the human brain use these environmental regularities for object recognition? Contextual associations are processed using a network including the parahippocampal cortex (PHC; Bar & Aminoff, 2003). We propose that a partially analyzed version of the input image (i.e., a blurred image) is projected rapidly from early visual areas to the PHC. This rudimentary representation activates an experience-based “guess” about the present context (i.e. a context frame). This information is then projected to the inferior temporal cortex, where it activates the representations of the objects associated with the specific context frame (Bar, 2004). When the coarse input to the PHC is ambiguous, it will result in the activation of multiple such context frames. We tested a rather counter-intuitive prediction of this model, best explained with an example: A picture of a gun, when projected rapidly in a blurred (i.e., low spatial frequency) form to the PHC, may be interpreted also as a drill and a hairdryer. These three objects are associated with three different context frames, and will subsequently trigger the activation of three sets of objects. Consequently, a gun will not only prime the recognition of a police car (i.e., contextual priming), but also the recognition of a hairbrush (i.e., a member of the context frame activated by the hairdryer), despite the lack of a perceptual or contextual relation between a gun and a hairbrush. Indeed, we found significant priming for this condition. Furthermore, we found that this indirect priming existed for relatively short-duration (250 ms), but not longer (1000 ms), exposures. This supports our notion that the arrival of additional information leaves only the most relevant context frame active. This novel result, along with neuroimaging data, elaborates the cortical mechanisms of top-down contextual facilitation of object recognition.
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