Heterogeneity in working memory performance caused by different positions of the visual cue in the visual field

It has been shown that a particular visual stimulus presented at a certain region of the visual field is more effectively processed in perceptual tasks, indicating that visual information is processed heterogeneously across the visual field. However, it remains unclear whether such spatial heterogeneity in perception extends to working memory (WM) performance across the visual field. To examine this issue, we used two n-back tasks and examined WM performances by systematically changing spatial positions of memorized cues in the visual field (16 positions in each of three eccentricities) and by changing task demands (continuous updating vs. selective encoding based on task-relevant cues). For analysis, we adapted signal detection theory to estimate the perceptual sensitivity and response bias instead of raw accuracies. Sensitivity was affected by polar angle positions and higher sensitivity was observed in the lower visual field across all conditions. The best sensitivity was observed in the 16° condition in both working memory tasks. Response bias was affected by both polar angle positions and eccentricities. A more balanced response bias (i.e., closer to zero) was present in the 24° eccentricity condition but not in 8° or 16° conditions. Shorter RTs were observed when memorized items were presented in the lower right visual quadrant. These results indicate that working memory performance exhibits systematic spatial heterogeneity across the visual field, and that this effect is robust across different task demands.