Attention modulates the activity of sensory areas by both increasing the activity in regions responding to attended stimuli and reducing activity in other regions. It is unclear, however, whether neural mechanisms of attention vary with perceptual requirements.
To answer this question, Sylvester et al. measured prestimulus preparatory brain activity while subjects performed nearly identical visual tasks. One task (threshold detection) used low-contrast stimuli that were easily distinguishable from each other but difficult to distinguish from background, whereas the other task (discrimination) used high-contrast stimuli that were difficult to distinguish from each other.
As expected, in both tasks, prestimulus activity increased in visual cortical regions representing the attended area and decreased in nontarget areas. But in the threshold detection task, activity was lower in nontarget areas, particularly the peritarget area, compared to in the discrimination task, suggesting that attention mechanisms vary depending on task requirements.-Society for Neuroscience
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