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

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.

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.

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.

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.