Nonlinear shift along the sensorimotor-association-axis in brain responses to task performance

In the literature of cognitive neuroscience, researchers tend to assume a linear relationship between brain activation level and task performance; however, conflicting findings have been reported in different studies. Therefore, there may be a non-linear relationship between task performance and brain activation if a full range of task performance is considered. In the current study, using the Human Connectome Project (HCP) dataset, we examined the relationship between brain activation (i.e., beta values) and working memory performance in four conditions (i.e., faces, body parts, tools and places). We found a gradual change along the sensorimotor-association (S-A) axis, with the higher-rank regions showing greater concavity (an inverted U-shaped curve) than the lower-rank regions only in the face and body part conditions. In the tool and place condition, very few high-order regions show a relationship with performance; therefore, the association with S-A ranking is missing. Instead, in the place condition, many regions showed a convex pattern with task performance. Moreover, the inflection point is above the average performance in the concave regions and below the average in the convex regions. In summary, our study revealed a novel functional property of the brain in response to task performance along the S-A axis.