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Nicole Hakim, Kirsten Adam, Eren Gunseli, Edward Vogel; Sustained spatial attention is not sufficient to elicit the Contralateral Delay Activity. Journal of Vision 2017;17(10):862. doi: 10.1167/17.10.862.
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© ARVO (1962-2015); The Authors (2016-present)
The Contralateral Delay Activity (CDA) is a popular neural measure used to track storage in visual Working Memory (WM). The amplitude of the CDA increases with the number of memoranda, asymptotes around 3 items, and is sensitive to individual differences in behavior. However, there is still debate about whether the CDA reflects WM contents or sustained spatial attention. WM tasks place high demands on sustained spatial attention, so attention and WM demands have been confounded in previous work. Here, we tested whether the CDA manifests when demands for sustained spatial attention are high, but demands for WM storage are absent. In the WM task, participants performed bilateral change detection for colored squares. In the attention task, participants had to continuously attend to locations that were previously occupied by squares and report the orientation of a rare target line during the blank period. Thus, the squares that served as memoranda in the WM condition, served as spatial cues indicating the likely position of the target in the attention condition. As expected, we found a large, sustained CDA during the WM task. Additionally, there was a set size effect for the WM task, with larger amplitude for set-size 4 than set-size 2. For the attention condition, by contrast, the CDA was entirely absent for both set sizes. In a follow-up experiment, which required finer spatial precision to discriminate the targets, there was also no evidence for the CDA during the attention task. However, during the attention task in each experiment, we observed a known marker of spatial attention (sustained contralateral alpha suppression), which provides positive evidence that subjects were indeed sustaining spatial attention throughout the trial. Given these results, we find no evidence that sustained spatial attention alone can drive the CDA, which supports claims that this activity reflects memory storage.
Meeting abstract presented at VSS 2017
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