Frequency-dependent and temporal variability of low-frequency fluctuations in patients with primary Sjögren's syndrome.

Objectives: The central nervous system is a significant extraglandular target in primary Sjögren's syndrome (pSS), often characterised by cognitive deficits. However, the underlying mechanisms remain elusive. This study aims to investigate the alterations in amplitude of low-frequency fluctuations (ALFF) in patients with pSS and to explore whether it exhibits frequency dependence and temporal variability, attempting to explore its mechanism.

Methods: The study comprised 68 patients with pSS and 69 healthy controls, all of whom underwent resting-state functional MRI and neuropsychological assessments. The ALFF method was used to ascertain whether frequency-dependent alterations occur within the slow-5 (0.01-0.027 Hz) and slow-4 (0.027-0.073 Hz) frequency bands. Additionally, dynamic ALFF (dALFF) analysis was conducted to explore the temporal variability. Ultimately, the correlation between the abnormal brain regions and neuropsychological assessments was elucidated.

Results: The right fusiform gyrus of patients with pSS shows abnormalities in ALFF and its two sub-bands, while the left precentral gyrus and right middle frontal gyrus exhibited abnormal increase limited to the slow-5 frequency band. dALFF showed an abnormal activity in the left supplementary motor area in patients with pSS. Additionally, the differential brain regions identified by the slow-5 frequency band of ALFF correlated with certain neuropsychological scales.

Conclusions: This research indicates that ALFF metrics offer enhanced insights into the alterations of regional brain function in patients with pSS, which exhibits both frequency-dependent and temporal variability characteristics, complementing traditional metrics and enhancing our comprehension of brain function in pSS and suggests that ALFF may emerge as a novel instrument for exploring the underlying neural mechanisms in patients with pSS.