Dr. Anna-Lisa Schuler | Flexible Adaptation of the Semantic Network: A multinodal perturbation approach using TMS and fMRI in healthy young participants

Flexible adaptation to varying task demands or lesions is one of the core features of the human brain, maintaining efficient interaction with the world. In this respect, the semantic network is of special interest since its intact functioning is not only crucial for human communication, but also interpretation of the world and thus meaningful participation in social life. Yet, little is known about the neuro-behavioral mechanisms underlying adaptation of the semantic network. Lesion and transcranial magnetic stimulation (TMS) studies have suggested compensatory effects including a stronger recruitment of the multiple demand network (MDN) after semantic network perturbation. However, it remains an open question how the upregulation of compensatory brain nodes contributes to the maintenance of cognitive functions in the case of acute perturbations.

To answer this question in the intact brain, the transient perturbation of multiple brain hubs is necessary. Simultaneous TMS-fMRI offers the possibility to investigate acute neuro-behavioral adaptation in response to perturbation in healthy participants.

This study will investigate the impact of stepwise increasing interference with nodes of the semantic as well as the multiple demand network on the recruitment of neural resources and semantic task performance. To this end, we will additively perturb these nodes combining TMS of multiple sites before and during the task with interleaved imaging. Specifically, we will first use a semantic matching task during functional imaging that has been shown to result in robust and replicable BOLD changes in health and disease to identify subject-specific nodes of the semantic network. We will then perturb two core-nodes of the semantic network with TMS to identify adaptive changes in response to network perturbation with fMRI. Finally, combining TMS before fMRI and concurrent TMS-fMRI, we will interfere with the semantic as well as the proposed compensatory MDN to investigate if this results in full decompensation of neuro-cognitive processing.