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Jennifer Lechak, Andrew Leber; Moment-to-Moment Fluctuations in Attentional Distraction by Motion: An fMRI Analysis. Journal of Vision 2011;11(11):95. doi: 10.1167/11.11.95.
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While many researchers characterize attention as a mechanism dominated by either goal-driven (“top-down”) or stimulus-driven (“bottom-up”) processing, it is possible that attention routinely shifts along a continuum between these processes. Recent neuroimaging work has supported this possibility, showing moment-to-moment fluctuations in pretrial fMRI activity predict the magnitude of behavioral distraction by irrelevant color singletons (Leber, 2010, J Neurosci). Specifically, greater pretrial activity in middle frontal gyrus predicted diminished distraction. What remains unknown is whether and how fluctuations in attentional control regions like MFG interact with early perceptual processing of stimuli in visual cortex. In the current study, designed to address this question, we scanned participants who searched for a target square among nontarget circles. A motion singleton distractor (a nontarget) appeared on 50% of trials. Choosing a motion distractor allowed us to examine trial-by-trial variations in how the distractor was processed by motion-sensitive visual regions (MT/MST). Results showed that fluctuations were predicted in distraction to motion using pretrial fMRI activity in several regions. Specifically, greater pretrial activity in left precentral gyrus predicted greater resistance to distraction. In contrast, greater pretrial activity in left superior temporal sulcus and precuneus predicted greater susceptibility to distraction; this latter finding is consistent with the placement of these regions in the “default network,” which is anticorrelated with frontoparietal control regions. Analysis of trial-evoked activity in MT/MST failed to show modulations of distractor processing as a function of pretrial activity in regions that predicted distraction. Therefore, fluctuations in attentional control may not be evident in early stages of visual processing, although important limitations of this analysis will be discussed. In summary, distraction by motion varies on a momentary basis and is predictable using baseline fluctuations in fMRI activity from multiple distinct regions of cortex.
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