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Free keywords:
Network connectivity; cTBS; Plasticity; Default mode network
Abstract:
The inferior parietal lobe (IPL) is an important hub of neural network function across multiple cognitive states, contributing to “task-negative” networks (default mode network; DMN) and “task-active” networks. To investigate flexible network behavior in cognition, we combined spaced double continuous theta burst stimulation (cTBS) with functional magnetic resonance imaging (fMRI) in both task and rest states. Thirty healthy, young volunteers participated in three measurements, in which posterior IPL was targeted using either right, left, or sham cTBS, prior to a three-task fMRI experiment encompassing the key cognitive domains attention, semantics, and social cognition. Additionally, all participants completed three pre-post stimulation resting-state fMRI sessions.
Independent component analysis was applied to pre-stimulation resting-state data to identify intrinsic connectivity networks. The detected networks guided back-projection to post-stimulation task data for each subject and session. Using correlational psychophysiological interaction analysis, network interactions were characterized across cognitive domains and stimulation conditions. ANOVAs and post-hoc t-tests within each domain showed that cTBS most effectively influenced network interaction in order of decreasing task complexity, starting from social cognition, followed by semantics and attention. During social cognition, compared to sham, right-hemisphere stimulation increased right fronto-parietal control (rFPCN) and somatomotor network interaction (p=0.0139), as well as ventral and dorsal attention network interaction (p=0.045). Left-side stimulation increased ventral attention-to-somatomotor network connectivity (p=0.017) and decreased dorsal attention and DMN subnetwork connectivity (p = 0.016). Right-side stimulation increased interaction between posterior DMN and rFPCN during the semantic task (p=0.012), and between the somatomotor network and a DMN subnetwork during the attention task (p=0.059). Collectively, our results demonstrate that, rather than inducing local changes, cTBS influences large-scale network interactions in a task-specific manner. The observed patterns suggest that more complex cognitive tasks show increased responsiveness to stimulation, with more distributed changes across networks and distinct, hemisphere-specific patterns between task-positive and task-negative network interactions.
