The selectivity of task-dependent attention varies with surrounding context.

Area of Science:

• Neuroscience
• Cognitive Science
• Visual Perception

Background:

• Attention enhances target processing and suppresses surrounding stimuli.
• The spatial spread of attention is hypothesized to be influenced by the relationship between the target and its surround.

Purpose of the Study:

• To investigate how the spatial profile of attention is modulated by the contextual relationship between a visual target and its surround.
• To examine the spread of attention into the surround under different segmentation conditions.

Main Methods:

• High-density electroencephalography (EEG) was used to measure brain activity.
• Frequency-tagged steady-state visual-evoked potentials (SSVEPs) probed the spread of attention.
• Participants detected contrast increments on a target grating surrounded by an annulus under varying segmentation conditions (contiguous vs. segmented).
• Brain responses were analyzed in five visual regions of interest (ROIs) including V1, V4, V3A, lateral occipital complex, and human middle temporal area.

Main Results:

• Attention generated smaller neural responses in the surround when the target was contiguous with it compared to when it was clearly segmented.
• Task success, requiring target selection and surround suppression, was influenced by segmentation.
• Neural responses in most ROIs reflected this modulation of attentional spread.

Conclusions:

• The spatial profile of attention is not fixed but dynamically adjusts based on task demands and the visual context.
• Attention focuses more tightly when a target needs to be isolated from its surround.
• Attention spreads more broadly when the target is clearly segmented from the surround.