Neural correlates of span capacity during visual discrimination under varying cognitive demands

This study examined the neural correlates of individual differences in span capacity during a visual discrimination task under varying cognitive demands. Thirty-six participants (ages 19-33) completed span tasks to assess cognitive capacity and were categorized into high- and low-span groups. Behavioral results showed that reaction times (RTs) increased and accuracy decreased with task difficulty, with individuals of higher span capacity exhibiting faster RTs and greater accuracy across conditions. Whole-brain analysis revealed distinct activation patterns: individuals with higher span capacity demonstrated more localized activation in anterior brain regions during complex tasks, while those with lower span capacity exhibited broader activation in posterior areas. The most demanding condition accentuated these differences, with higher-span individuals showing stronger BOLD responses in both anterior and posterior regions, whereas low-span capacity exhibited broader activation in posterior areas, suggesting more widespread neural engagement. Searchlight-based multivoxel pattern analysis further confirmed these group differences. Additionally, regression analyses, rather than the median-split approach, produced similar results. These findings reveal that neural activation patterns under cognitive load vary with individual differences in span capacity, pointing to distinct patterns of neural activity related to cognitive demands.