Altered brain network dynamics in motor functional neurological disorders: the role of the right temporo-parietal junction

Functional neurological disorders' (FND) neuropathophysiology has been described as multi-network disturbances including aberrancies in the agency network highlighting the role of the right temporo-parietal junction (rTPJ). Refining the relevance of the rTPJ, we applied a co-activation pattern (CAP) based approach using the rTPJ as a seed in 58 patients with motor FND compared to 58 age- and sex-matched healthy controls (HC). Firstly, CAPs were derived from HC to identify functional alterations in the rTPJ network in FND patients. Secondly, motor subgroup characteristics in patients were examined using CAPs derived from the patient group. Compared to HC, patients were found to enter less frequently a state characterized by salience network and default mode network (DMN) co-activation along with executive control and somatomotor networks co-deactivation. Additionally, patients entered more often a state depicted by somatomotor-salience co-activation and DMN co-deactivation. Comparing motor subgroups, patients with functional weakness (FW) remained longer in a state characterised by salience and dorsal/ventral attention network co-activation and DMN co-deactivation compared to patients with no functional weakness (no-FW). FND patients overall exhibited a reduced coupling of the DMN and an increased coupling of the somatomotor network with the rTPJ compared to controls. Patient subgroups differed regarding coupling between the rTPJ and the attention network and DMN. rTPJ dynamic network alterations might reflect hampered flexibility in brain state switching and altered self-referential processes linked to impaired motor planning and execution, which seem to also differ between symptom types, indicating a potential phenotypic biomarker.