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Johannes Fahrenfort; Neural markers of perceptual integration without attention. Journal of Vision 2015;15(12):1397. doi: 10.1167/15.12.1397.
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A number of studies have shown that object detection and object categorisation can occur outside consciousness, and are largely mediated by feedforward connections in the brain. Conscious object perception on the other hand, requires a process of neuronal integration mediated by recurrent connections. The question I will address in this talk, is to what extent this process of integration requires attention. Traditionally, recurrent processing has been associated with top down attention and control. However, going against a long tradition in which attention is thought to cause feature integration, a number of studies suggest that feature integration also takes place without attention. This would imply that neuronal integration does not require attentional control. In a recent EEG experiment, we tested whether neural markers of feature integration occur without attention. Employing a 2 by 2 factorial design of masking and the attentional blink, we show that behaviourally, both masking and attention affect the degree to which subjects are able to report on integrated percepts (i.e. illusory surface perception in a Kanizsa figure). However, when using a multivariate classifier on the EEG, one can decode the presence of integrated percepts equally well for blinked and non-blinked trials, whereas masking selectively abolishes the ability to decode integrated percepts (but not features). This study uncovers a fundamental difference in the way attention and masking impact cortical processing. Together, these data suggest that feature integration does not require attention, whereas it is abolished by masking.
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