Abstract
BackgroundThe load theory of selective attention hypothesizes that distractor interference is suppressed after perceptual processing (i.e., in the later stage of central processing) at low perceptual load of the central task, but in the early stage of perceptual processing at high perceptual load. Consistently, studies on the neural correlates of attention have found a smaller distractor-related activation in the sensory cortex at high relative to low perceptual load. However, it is not clear whether the distractor-related activation in brain regions linked to later stages of central processing (e.g., in the frontostriatal circuits) is also smaller at high rather than low perceptual load, as might be predicted based on the load theory.Methodology/Principal FindingsWe studied 24 healthy participants using functional magnetic resonance imaging (fMRI) during a visual target identification task with two perceptual loads (low vs. high). Participants showed distractor-related increases in activation in the midbrain, striatum, occipital and medial and lateral prefrontal cortices at low load, but distractor-related decreases in activation in the midbrain ventral tegmental area and substantia nigra (VTA/SN), striatum, thalamus, and extensive sensory cortices at high load.ConclusionsMultiple levels of central processing involving midbrain and frontostriatal circuits participate in suppressing distractor interference at either low or high perceptual load. For suppressing distractor interference, the processing of sensory inputs in both early and late stages of central processing are enhanced at low load but inhibited at high load.
Highlights
Attention facilitates goal-directed behavior by focusing on targets and inhibiting interference from distractors
Multiple levels of central processing involving midbrain and frontostriatal circuits participate in suppressing distractor interference at either low or high perceptual load
The processing of sensory inputs in both early and late stages of central processing are enhanced at low load but inhibited at high load
Summary
Attention facilitates goal-directed behavior by focusing on targets and inhibiting interference from distractors. The central processing passively excludes distractors from processing at high load because central tasks may consume all processing resources [5,6,8] Because this theory hypothesizes that the brain actively processes distractors at low load more so than at high load, one might predict that both early and late stages of central processing will show a greater distractor-related activation at low relative to high load. Studies on the neural correlates of attention have found a smaller distractor-related activation in the sensory cortex at high relative to low perceptual load It is not clear whether the distractor-related activation in brain regions linked to later stages of central processing (e.g., in the frontostriatal circuits) is smaller at high rather than low perceptual load, as might be predicted based on the load theory
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