Negative BOLD Responses Surpass Positive Responses in Task Specificity, Reflecting Neural Reconfigurations Better Than Functional Connectivity.

OBJECTIVE

To investigate whether the Negative BOLD Response (NBR) is more task-specific than the Positive BOLD Response (PBR) during cognitive tasks and to determine whether task-evoked activity reflects brain reconfigurations during different tasks better than functional connectivity.

METHODS

Functional Magnetic Resonance Imaging (fMRI) data were collected from 214 participants under 50 years old (152 in Dataset 1 and 62 in Dataset 2) performing twelve cognitive tasks spanning vocabulary, speed of processing, fluid reasoning, and memory domains. Data analysis included subject-level and group-level analyses, focusing on comparing the spatial patterns and task specificity of NBR and PBR through similarity measures using Dice coefficients. Additionally, functional connectivity was assessed using the Multi-session Hierarchical Bayesian Model (MS-HBM) to evaluate its sensitivity to task-induced brain reconfigurations compared to task-evoked activity.

RESULTS

NBR demonstrated significantly greater task specificity compared to PBR across all cognitive tasks, with lower mean Dice coefficients for NBR maps (mean: 0.44, SD: 0.13) than for PBR maps (mean: 0.67, SD: 0.09; t(65) = 18.38, p < 0.001). Functional connectivity analyses indicated that the default mode network (DMN) remained stable across tasks, suggesting that task-evoked activity reflects task-specific brain reconfigurations better than functional connectivity.

CONCLUSION

The findings confirm that NBR is inherently more task-specific than PBR and that task-evoked activity provides a more sensitive measure of task-specific neural reconfigurations than functional connectivity. This enhances our understanding of the neural mechanisms underlying cognitive processes and highlights the importance of considering NBR in cognitive neuroscience research.