Attention and working memory: Disrupting feature binding in visual working memory

ATTENTION AND WORKING MEMORY: DISRUPTING FEATURE BINDING IN VISUAL WORKING MEMORY By Jonathan G. Hakun In the current study we investigated disruption of working memory for multi-feature visual objects through a visual change detection paradigm modified with a distraction manipulation (termed the “Binding Distraction Task”). The paradigm included three processing stages (study, maintenance, and test) with a distraction event presented during maintenance. The judgment performed on each trial involved deciding whether a single two-feature test object (a colored shape) contained the same or changed combination of shape and color as one of the study objects (i.e. contained the same feature binding). The distraction event involved presenting an array of visual objects arranged spatially in a manner similar to the study array. We compared performance on trials where distraction arrays contained objects sharing feature-overlap with the current trial’s study objects (matched arrays) with trials where distracter objects contained study-related features but no overlap with the current trial’s study set (related arrays). As compared with trials involving empty distraction arrays and baseline performance (no distraction), the presentation of matched arrays was consistently disruptive of binding change detection performance across all of the experiments presented here. The performance cost associated with related arrays however was more variable across experiments. Through an individual differences approach, we investigated an executive gating account of the distraction effect. That is, disruption is caused by a failure to keep distracter objects from reaching visual working memory (VWM) thereby displacing study objects. Based on this account we predicted that individuals with high working memory capacity (WMC), as measured through complex span and single feature change detection task performance, should be more resistant to distraction than low WMC individuals. However, the results of our individual differences analysis failed to provide support for the executive gating hypothesis (costs were unrelated to WMC). Alternatively, we proposed that distraction costs may reflect a special case of contingent attention capture. That is, attention may be biased toward distracter objects that overlap with the features active in VWM. To explore this hypothesis further we additionally conducted an fMRI study. The results of our fMRI analysis indicated that regions of the brain that are commonly involved in the voluntary and stimulus-driven control of attention responded in a manner consistent with our contingent capture hypothesis. Regions involved in the voluntary control of attention (superior parietal and prefrontal) parametrically scaled in activation in accordance with the proposed demands associated with each distraction condition. However, as further evidence against the executive gating hypothesis, activation in all of the regions involved in voluntary control did not relate to performance costs. On the other hand, regions associated with the contingent capture of attention (specifically, the right ventrolateral prefrontal cortex, VLPFC, and temporo-parietal junction) only reliably responded to the filled distracter arrays (related and matched arrays). Further, activation within the right VLPFC was positively related to the performance cost observed in both conditions. Altogether the results of the current study support a stimulus-driven account of disruption of VWM for bound features. Specifically, we conclude that maintaining multiple bound representations in VWM creates a context in which distracter objects containing feature-overlap capture attention and result in the downstream impoverishment of stored representations.