Fig. 4: Difficulty effects of spatial working memory and math tasks and their intersection with semantic tasks.

a, b Difficulty effects in spatial working memory and math tasks, respectively. Warm colors indicate regions with increased activation during harder trials, while cold colors show regions with greater activation in easier trials (p < 0.05, FDR-corrected). c Overlap of regions with positive difficulty effects in the semantic association task (orange) and those responsive to non-semantic control demands (turquoise). d Overlap of regions with positive difficulty effects in the semantic feature matching task (yellow) and those responsive to non-semantic control demands (green). Red regions indicate difficulty effects present in both semantic tasks but not in the non-semantic tasks. e Greater difficulty effect in semantic feature matching compared to semantic association task within MDN regions (i.e., overlapping regions showing positive effects of difficulty in both spatial working memory and math tasks). f The global minimum distance to sensory-motor cortex for four types of parcels in c and d, each exhibiting a different pattern of difficulty across tasks. These groups of parcels showed a gradient in their distance from sensory-motor cortex: association-only parcels were the most distant, followed by association and non-semantic parcels, then feature and non-semantic parcels, with feature-only parcels being the closest. (***p = 0.001, FDR corrected).