The connectivity between Insula and Precuneus may be associated with cognitive function in patients with isolated sleep behavior disorder (iRBD) with rapid eye movements, according to the results of a cross-sectional study published in Sleep Medicine.
Study researchers recruited patients (n = 50) diagnosed by video polysomnography with iRBD at the Sleep Clinic at Seoul National University Hospital and healthy controls (n = 20) for this study. They assessed participants through multivariate pattern analysis based on structural magnetic resonance imaging (MRI) and functional MRI scans at rest.
Patients with iRBD and patients in the control group had a mean age of 66.5 years (standard deviation) [SD]± 6.9) and 68.1 (SD, ± 3.4) years and 58.0% and 55.0% were men. Patients were diagnosed with iRBD an average of 7.1 (SD, ± 4.6) years ago, and compared to controls they had higher scores for the questionnaire on sleep disorder with rapid eye movements (P <0.001) and the Geriatric Depression Scale ( GDS; P =). 001), Scales for Outcomes in Parkinson Disease-Automatic Questionnaire Scores (P = 0.001) and fewer years spent in education (P = 0.047).
The multivariate pattern analysis revealed 1 significant cluster in the left posterior islet cortex and 2 in the precuneus.
Patients with iRBD showed a positive correlation between the functional connectivity of the insular precuneus cluster 1 and the MoCA scores (Montreal Cognitive Assessment) (r, 0.317; P = 0.025). The MoCA values showed a positive correlation with the functional connectivity of the Precuneus cluster 2 (r, 0.271; P = 0.057).
GDS and MoCA scores were negatively correlated (r, -0.294; P = 0.038). After adjustment for GDS, the MoCA scores correlated with the functional connectivity in both clusters in the Precuneus (cluster 1: adjusted r, 0.337; P = 0.018; cluster 2: adjusted r, 0.371; P = 0.009).
The delayed recall correlated with the functional connectivity of cluster 2 in the left posterior insula (r, 0.282; P = 0.047) and was more strongly correlated after correction of the GDS (adjusted r, 0.333; P = 0.019).
This study was limited due to its small sample size and cross-sectional design, which made it impossible to assess the causal relationships.
The study’s researchers concluded that their results “use the insula as an important neural correlate in the context of iRBD … [Functional connectivity] Change can be a biomarker of incipient cognitive decline, and larger longitudinal studies will be needed to confirm the causal relationship between FC changes and cognitive impairment in iRBD. ”
Byun JI, Cha KS, Kim M. et al. Altered island functional connectivity in isolated REM sleep behavior disorder: a data-driven functional MRI study. Sleep Med. 2021; 79: 88- 93. doi: 10.1016 / j.sleep.2020.12.038