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Todd Kelley, Nilli Lavie; Working memory load alters response to stimuli in early visual cortex. Journal of Vision 2009;9(8):166. doi: 10.1167/9.8.166.
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Previous research has established that load on cognitive control functions such as working memory impairs executive control of selective visual attention. This results in greater distractor interference effects (Lavie, 2000; Lavie et al., 2004) and increased distractor-related activity in category-selective visual association cortex (e.g. fusiform face area response to distractor faces, De Fockert et al. 2001) under conditions of high working memory load. It remains unclear whether these effects reflect a modulation of high-level semantic processing or whether effects of working memory load on attention extend to the processing of distractors in striate and extrastriate visual cortex. We used fMRI to examine this question by assessing the response in retinotopic cortex to irrelevant (but response-competing) distractor objects presented during a selective attention task under either high or low working memory load. Participants held either one digit (low load) or six digits (high load) in working memory while classifying an object as either a household item or a fruit. The target object could be accompanied by a distractor that was either the same object (congruent) or an object from the opposite category (incongruent). The incongruent (vs. congruent) distractors produced greater response competition effects on the target RTs under high load than low load. fMRI results mirrored this behavioral pattern: there was a greater neural response in early visual cortex (areas V1–V4) for incongruent compared to congruent distractors under high compared to low working memory load. These findings support the load theory of attention and cognitive control and are the first to demonstrate effects of high level cognitive control by working memory on distractor-related activity in early retinotopic visual cortex.
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