Push-pull mechanism of selective attention in human extrastriate cortex

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Perception

Background:

• Selective attention enhances processing of attended stimuli within the visual cortex.
• The neural processing of unattended stimuli, particularly outside the focus of attention, remains less understood.
• Understanding how the brain filters distractors is crucial for comprehending visual perception.

Purpose of the Study:

• To investigate the neural fate of unattended stimuli during selective attention.
• To examine the effect of attentional load on the processing of both attended and unattended visual stimuli.
• To identify the brain regions and mechanisms involved in filtering distractors.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed to measure brain activity.
• Attended (target) and unattended (distracter) stimuli were presented simultaneously in opposite visual hemifields.
• Subjects performed low and high attentional-load search tasks, directing attention covertly.

Main Results:

• Activity related to attended targets increased with higher attentional load in visual areas.
• Activity related to unattended distractors decreased with higher attentional load in areas V4 and TEO, but not in early visual areas (V1, V2).
• A distributed frontoparietal network showed activity related to target selection during spatially directed attention.

Conclusions:

• Evidence supports a load-dependent 'push-pull' mechanism of selective attention operating across large visual field portions at intermediate processing stages.
• This mechanism appears to be regulated by a frontoparietal network involved in target selection.
• The findings elucidate how the brain manages competing visual information under varying attentional demands.