Short-term intrinsic connectivity changes induced by cognitive exertion in healthy participants

Introduction: Changes in brain intrinsic connectivity on the timescale of minutes, as provoked by a cognitive task, have not been well documented. Methods: A total of two 7.5-min 7 Tesla functional MRI (fMRI) scans (Run 1 and Run 2), separated by 90 s, were acquired for 23 healthy participants during cognitive exertion induced by the Stroop color-word interference task. Independent component analysis (ICA) of the paired Run 1 and Run 2 fMRI acquisitions identified components with distinct spatial and temporal signatures. Results: The spatial extent of the ICA components coincided with hubs of the brain's intrinsic networks. In addition, these components correlated with brain regions from other networks, thereby defining inter-network connectivity. Run 1 and Run 2 showed significantly different patterns of connections (p-FWE < 0.01) across 10 ICA-identified intrinsic networks and 20 inter-networks. Connectivity in Run 2 was higher in 12 nodes and lower in eight nodes, indicating dynamic changes during the task response. Overall, the right angular gyrus/supramarginal gyrus and the right frontal pole regions of the ventral attention network showed greater activity in Run 1, but activity shifted to the fusiform gyrus, supplementary motor area (SMA), and precentral and postcentral gyrus nodes in Run 2. Response times (RTs) and Stroop test accuracy did not change between runs in these healthy participants. Conclusion: Inter-network connectivity indicated that surveillance and task oversight nodes were required early in learning how to complete the Stroop task (Run 1), but these were replaced by object recognition and more automatic responses in Run 2. These findings define inter-networks that are sensitive to cognitive exertion and provide a framework for understanding cognitive dysfunction.