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Eva Feredoes, Klaartje Heinen, Jon Driver; Causal evidence for the role of prefrontal cortex in the control of sub- and suprathreshold distracters. Journal of Vision 2012;12(9):1333. doi: 10.1167/12.9.1333.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work has shown that, paradoxically, subthreshold visual motion distracters can disrupt task-relevant performance to a greater extent than suprathreshold distracters. Moreover, activation of the dorsolateral prefrontal cortex (dlPFC) increases for supra- versus subthreshold distracters, suggesting that successful top-down dlPFC control over distracters occurs when they are perceptually suprathreshold. To further investigate, we used the causal approach of applying transcranial magnetic stimulation (TMS) during functional magnetic resonance imaging (fMRI), a technique permitting causal visualisation of the interplay between brain regions under different cognitive conditions; here when motion distracters were presented above or below the perceptual threshold. In 15 participants we applied TMS over right dlPFC as they performed a centrally located visual letter detection task in the presence of task irrelevant moving dots whose motion coherence was manipulated to render them above or below the threshold for coherent motion direction perception. Participants also performed a task in which they were to now report the direction of coherent motion of the (previously irrelevant) moving dot stimuli. As anticipated, when the dots functioned as distracters and were subthreshold, letter task performance was worse and MT+ activity increased. TMS over right dlPFC further activated this region, and also MT+, when suprathreshold motion was present, but interestingly this was regardless of whether motion stimuli were distracters or task relevant. During the letter detection task in visual regions sensitive to the foveal presentation of letters, TMS increased activity but only for suprathreshold moving dot distracters. No such effect was produced when they were subthreshold suggesting that unless distracters are above the perceptual threshold, dlPFC does not influence posterior visual regions. Thus, by combining fMRI concurrently with a causal TMS intervention, we provide a new line of evidence that dlPFC does play a causal role to control interference by communicating with task-relevant versus irrelevant visual regions.
Meeting abstract presented at VSS 2012
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