Hemifield Specificity of Attention Response Functions during Multiple-Object Tracking.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Visuospatial Attention

Background:

• Multiple object tracking (MOT) difficulty increases with target number, modulating brain activity in attention networks.
• Attention Response Functions (ARFs) describe load-dependent activity, but hemispheric or hemifield imbalances were unexamined.
• Spatial attention exhibits hemifield/hemispheric effects, such as hemispatial neglect and capacity limits.

Purpose of the Study:

• To investigate whether hemispheric or hemifield imbalances exist in Attention Response Functions (ARFs).
• To determine how the number of tracked objects (load) influences brain activity across different visual hemifields.
• To extend the understanding of load-based ARFs by incorporating hemifield bias.

Main Methods:

• Functional magnetic resonance imaging (fMRI) using Blood-Oxygen-Level-Dependent (BOLD) signal.
• Participants (n=19) performed a multiple object tracking task with varying target loads.
• Analysis focused on differential brain activity related to contralateral versus ipsilateral target presentation.

Main Results:

• The number of tracked objects modulated activity bilaterally across a wide network of brain areas.
• Earlier visual stream areas showed contralateral load effects, while later areas responded to ipsilateral load.
• The dorsal attention network (parietal and frontal lobes) was significantly influenced by both contra- and ipsilateral load.
• Some occipital regions were more sensitive to contralateral than ipsilateral load.

Conclusions:

• The study extends the canonical view of load-based ARFs to include hemifield bias.
• Hemifield-preferring regions may impose processing bottlenecks, contributing to capacity and speed limits in MOT.
• Findings challenge existing explanations of hemispatial neglect and advance understanding of spatial attention and mental effort management.