rTMS modulates precuneus-hippocampal subregion circuit in subjective cognitive decline 

Abstract

Background: To identify whether repetitive transcranial magnetic stimulation (rTMS) could ameliorate the HIPsub network connectivity by modulating one node of hippocampal subregions (HIPsub) network in subjective cognitive decline (SCD) subjects.Methods: In the first cohort, we analyzed three HIPsub (HIPe, HIPc, and HIPp) functional connectivity to identify HIPsub network connectivity alterations that relate to SCD. And we further applied a SVM approach using the alterations to identify how well this could distinguish SCD from CN. In the second cohort, rTMS with 5-day of once-daily for 2 weeks was used to modulate the altered HIPsub network connectivity in a sham-controlled design.Results: SCD subjects showed differently altered patterns of HIPsub network connectivity compared to controls. The SVM classifier showed that the abnormalities had a high power to discriminate SCD from CN, with an ACC of 86.0%, an AUC of 92.9%, 83.8% sensitivity, and 89.1% specificity. Restoration of HIPc connectivity with left parahippocampa gyrus and HIPp connectivity with left middle temporal gyrus corresponded to amelioration of episodic memory in SCD patients after 2 weeks of rTMS. Conclusion: rTMS can restore the posterior hippocampus connectivity by modulating the precuneus in SCD subjects. Correction of breakdown in HIPc and HIPp related to cognitive and perceptual processing can simultaneously ameliorate episodic memory in SCD subjects.