Compensative inter-module functional connectivity enhancement at the latter half of verbal fluency task in patients with temporal lobe epilepsy.

BACKGROUND

Previous studies proposed that disrupted dynamic interaction between language subsystems diminishes temporal lobe epilepsy (TLE) patients' adaptability to changing cognitive loads. However, how the interaction is dynamically performed remained unclear. Due to the graphic syllabic logographic nature of Chinese characters, the Chinese Character verbal fluency (VFC) task provides changing demands throughout the task, being an ideal tool to analyze the dynamic interaction of language subsystems.

METHODS

Twenty-nine neurotypical controls and 58 patients with TLE from an ongoing cohort participated in this study. Functional MRI data was collected while participants performed a Chinese verbal fluency task. Functional connectivity alteration from the first to the second half of the task block were compared between controls and patients. Regions with significant functional connectivity changes are clustered into modules. The recruitment and integration of modules were calculated with sliding-window approaches and compared.

RESULTS

We captured the left frontal and anterior temporal lobe modules. The functional connectivity between the left frontal and anterior temporal modules was enhanced in the latter half of the VFC task in patients but not controls (p < 0.05, FDR-corrected). Meanwhile, TLE's functional connectivity within the anterior temporal module was impaired throughout the task (p = 0.04), and the two modules were more integrated in patients (p = 0.008). Intermodular connectivity enhancement in patients was correlated with better verbal fluency performance (p = 0.03, FDR-corrected).

CONCLUSION

We observed diminished intramodular and enhanced intermodular dynamic functional connectivity in patients with TLE. The enhanced intermodular functional connectivity at the latter half of the task represents a compensative process, a potential intervention target for language decline in TLE.