Parietal Lobe Reorganization and Widespread Functional Connectivity Integration in Upper-Limb Amputees: A rs-fMRI Study

Abstract

The right parietal lobe plays an important role in body image, and disorders of body image emerge after lesions in the parietal lobe or with parietal lobe epilepsy. Body image disorder also often accompanies upper-limb amputation, in which the patient misperceives that their missing limb is still part of their body. Cortical reorganization is known to occur after upper-limb amputation, but it is not clear how widespread and to what degree functional connectivity (FC) is reorganized post-amputation, nor whether such changes might be related to misperceptions of body image. Twenty-four subjects who had a traumatically upper-limb amputees (ULAs) and 24 age-matched healthy controls (HCs) underwent resting-state functional magnetic resonance imaging (rs-fMRI) scans. Regions of interest (ROIs) in the right superior parietal gyrus (SPG_R) and right inferior parietal lobule (IPL_R) were defined using BrainNet Viewer. We calculated the amplitude of low-frequency fluctuations (ALFF) in ROIs and correlated the ROI mean amplitude of low-frequency fluctuations (mALFF) and mean scores on the phantom limb sensation (PLS) scale and beck depression index (BDI). We also calculated ROIs and whole-brain FC. Compared to the HC group, we observed significantly increased activation (mALFF) in ROIs of the ULA group. Moreover, correlation analyses revealed a significant positive correlation between ROI mALFF and scores on the PLS. There was a significant negative correlation between the SPG_R mALFF and BDI scores. Seed-based, whole-brain FC analysis revealed that FC in the ULA group significantly decreased in many brain regions across the entire brain. The right parietal lobe appears to be involved in some aspect of body awareness and depression in amputation patients. Upper-limb amputation results not only in reorganization in the local brain area formerly representing the missing limb, but also results in more widespread reorganization through FC changes in whole brain.

Altered cortical thickness and structural covariance networks in upper limb amputees: A graph theoretical analysis

“…In our previous studies, both functional connectivity and functional brain network analyses demonstrated that significant changes also occur in this region 12,13 . These findings from this study provide further evidence supporting the coupling of function and structure, which will guide us in future studies of the CRT after amputation.…”

“…In our previous studies, both functional connectivity and functional brain network analyses demonstrated that significant changes also occur in this region. 12 , 13 These findings from this study provide further evidence supporting the coupling of function and structure, which will guide us in future studies of the CRT after amputation. Interestingly, our correlation analysis with clinical manifestations showed that the decrease in CTh was negatively correlated with PLP score, which suggests that lower CTh was associated with more intense PLP.…”

“…CRT theory has played a major role in focusing the field, from functional to structural, from single subject studies to group studies, from study of discrete local brain regions to brain network‐level studies 8 . Our previous imaging studies have produced new insights into brain remodeling patterns after upper limb amputation, specifically from changes in different levels of functional connectivity to changes in network connectivity 12,13 . Neural structure forms the substrate for functionality, and the integrity or change in that structure will greatly affect brain function.…”

“… 8 Our previous imaging studies have produced new insights into brain remodeling patterns after upper limb amputation, specifically from changes in different levels of functional connectivity to changes in network connectivity. 12 , 13 Neural structure forms the substrate for functionality, and the integrity or change in that structure will greatly affect brain function. Currently, structural magnetic resonance imaging (MRI) studies using voxel‐based morphometry or surface‐based morphometry (SBM) have also demonstrated significant structural changes in the brain after amputation.…”