Functional specialization for feature-based and symmetry-based groupings in multiple object tracking

Abstract

Our vision systems utilize attention to process dynamic visual information everyday. Multiple object tracking (MOT) is widely used for studying sustained attention in dynamic environments. Previous research reported inter-target grouping based on feature similarity (e.g., targets sharing the same color, size, or shape) can facilitate tracking. A recent study also found that symmetric relation among targets in MOT tasks can automatically improve tracking performance, and a greater grouping effect based on symmetry and feature was observed. However, grouping based on multiple feature cues didn't produce a greater grouping effect than grouping based on one feature cue. Why were groupings based on symmetry and feature additive, but two feature-based groupings were not? How stimulus-driven inter-target groupings based on color or symmetry improve the goal-directed target tracking process remains unknown. We hypothesized that symmetry-based and feature-based groupings would involve different cortical and subcortical areas, and color-based and color-shape-based groupings would be manifested in significant activity in the same regions. This study used functional magnetic resonance imaging (fMRI) to identify cortical and subcortical areas involved in feature-based and symmetry-based groupings respectively during tracking. The results of our experiment showed that lateral occipital (LO) cortex is involved in symmetry-based grouping during tracking. Bilateral putamen, temporal parietal junction (TPJ), and frontal eye field (FEF) are involved in the feature-based grouping. Our findings likely indicate that stimulus-driven inter-target symmetry-based grouping and feature-based grouping improve goal-directed target tracking in different ways.