Hippocampal-Subregion Mechanisms of Repetitive Transcranial Magnetic Stimulation Causally Associated with Amelioration of Episodic Memory in Amnestic Mild Cognitive Impairment

Abstract

Background: Altered hippocampal subregions (HIPsub) and their network connectivity relate to episodic memory decline in amnestic mild cognitive impairment (aMCI), which is significantly limited by over-dependence on correlational associations. Objective: To identify whether restoration of HIPsub and its network connectivity using repetitive transcranial magnetic stimulation (rTMS) is causally linked to amelioration of episodic memory in aMCI. Methods: In the first cohort, analysis of HIPsub grey matter (GM) and its functional connectivity was performed to identify an episodic memory-related circuit in aMCI by using a pattern classification approach. In the second cohort, this circuit was experimentally modulated with rTMS. Structural equation modeling was employed to investigate rTMS regulatory mechanism in amelioration of episodic memory. Results: First, in the first cohort, this study identified HIPsub circuit pathology of episodic memory decline in aMCI patients. Second, in the second cohort, restoration of HIPc GM and its connectivity with left middle temporal gyrus (MTG.L) are causally associated with amelioration of episodic memory in aMCI after 4 weeks of rTMS. Especially important, the effects of HIPc GM changes on the improvement of episodic memory were significantly mediated by HIPc connectivity with MTG.L changes in aMCI. Conclusion: This study provides novel experimental evidence about a biological substrate for the treatment of the disabling episodic memory in aMCI patients. Correction of breakdown in HIPc structure and its connectivity with MTG can causally ameliorate episodic memory in aMCI.

Altered Structural and Functional Patterns Within Executive Control Network Distinguish Frontal Glioma-Related Epilepsy

“…Magnetic resonance imaging data were pre-processed using Matlab (Math Works Inc., Natick, MA, United States) and SPM8. The image processing procedure was conducted per published studies ( Liu Y. et al, 2020 ; Chen et al, 2022 ). Briefly, the functional MRI (fMRI) image pre-processing steps included discarding the first 10 volumes, slice-timing, head motion corrections, spatial normalization, spatial smoothing, denoising, and temporal filtering ( Liu Y. et al, 2020 ; Chen et al, 2022 ).…”

“…The image processing procedure was conducted per published studies ( Liu Y. et al, 2020 ; Chen et al, 2022 ). Briefly, the functional MRI (fMRI) image pre-processing steps included discarding the first 10 volumes, slice-timing, head motion corrections, spatial normalization, spatial smoothing, denoising, and temporal filtering ( Liu Y. et al, 2020 ; Chen et al, 2022 ). A total of 2 non-FGep patents and 1 FGep patent were excluded from the subsequent analysis due to the excessive head movement (cumulative translation or rotation > 3.0 mm or 3.0°).…”

“…According to converging evidence ( Seeley et al, 2007 ; Fransson and Marrelec, 2008 ; Smith et al, 2009 ; Dong et al, 2020 ; Liu et al, 2021 ), this study selected the right DLPFC (MNI space: 48, 12, 34) to draw 6-mm spheres as seed region of interest (ROI) ( Seeley et al, 2007 ; Fransson and Marrelec, 2008 ; Smith et al, 2009 ; Dong et al, 2020 ; Liu et al, 2021 ). We performed a voxel-wise cross-correlation analysis between the individual averaged time series for all voxel within DLPFC and the whole brain within the patients’ group GM mask ( Chen et al, 2016a , 2022 ; Liu et al, 2021 ).…”

“…As described in previous studies ( Chen et al, 2022 ), an support vector machine (SVM) approach was applied to test how well GM, ReHo, and FC within ECN could distinguish non-FGep and FGep from CN subjects. We performed a linear SVM classifier using the LIBSVM software.…”

Stable functional compensation within hippocampal-subregion networks in patients with temporal glioma before and after surgery

“…Gliomas account for approximately 81% of malignant primary brain tumors ( Ostrom et al, 2014 ), with the second-highest proportion of temporal lobe invasion ( Ostrom et al, 2019 ). Damage to the temporal lobe, known to be located in the hippocampal memory network, can alter its function including memory processing, emotional processing, and sensory processing ( Chen et al, 2016 , 2020 , 2022 ). Interestingly, clinical observations have discovered that memory function remains intact among patients with temporal glioma.…”