Table 1.
Participant demographics.
Fig 1.
A. An unstable chair, developed to isolate trunk control, positioned atop a force plate. An adjustable hemisphere mounted under the chair makes sitting unstable and allows for standardization of position across different thigh lengths. The hips, knees, and ankles are positioned in 90 degrees of flexion, and straps are placed around the legs to minimize movement of the lower extremities. B. A safety bar positioned anteriorly allows participants to stabilize and rest the trunk muscles between trials. C. Two conditions were tested: eyes open (EO) and eyes closed (EC). D. 95% confidence ellipse area (CEA) around a single participant’s center-of-pressure (COP) tracing. 95% CEA represents how much a participant deviated from their mean COP.
Fig 2.
Cortical Sensorimotor Gray Matter Atlas for the Trunk (CSMGA-T).
The CSGA contains primary and secondary/supplementary sensorimotor brain regions of interest in both the left and right hemispheres, including the supplementary motor cortex, primary motor and somatosensory cortices, parietal operculum, and superior parietal lobule. The medial primary motor and somatosensory cortices were selected to focus our investigation on the gray matter considered most relevant to the trunk.
Fig 3.
Cortical Sensorimotor White Matter Tracts for the Trunk (CSMWT-T).
A. The CSMWT-T contains contiguous 3-dimensional tracts connecting 5 different cortical sensorimotor gray matter areas bilaterally, including the supplementary motor cortex, primary motor and somatosensory cortices, parietal operculum, and superior parietal lobule. B. The 2-dimensional representation of these tracts in the sagittal, coronal, and axial views.
Fig 4.
Seated trunk control performance by group and condition.
Left: Violin plots displaying the distribution of seated trunk control performance by condition for each group. The chronic low back pain group (cLBP) presents a bimodal distribution for both tasks. Both groups exhibit skewness towards poor performance. Right: Line plots representing group means and 95% confidence intervals for each condition. ANOVA reveals main effects for group (*; p < .001) and condition (±; p < .001), where the cLBP group performed more poorly than healthy controls, and both groups performed more poorly with eyes closed. A trend (p = .051) for a group x condition interaction was observed where the change in performance between eyes open and eyes closed was larger in the cLBP group.
Fig 5.
Scatter plots of cortical sensorimotor white matter microstructure and seated trunk control in chronic low back pain.
Top Left: Scatter plot of cortical sensorimotor tract fractional anisotropy (FA) and 95% Confidence Ellipse Area (CEA) for the eyes open (EO) condition. Top Right: Scatter plot of cortical sensorimotor tract FA and 95% CEA for the eyes closed (EC) condition. Bottom Left: Scatter plot of cortical sensorimotor tract radial diffusivity (RD) and 95% Confidence Ellipse Area (CEA) for the EO condition. Bottom Right: Scatter plot of cortical sensorimotor tract RD and 95% CEA for the EC condition.
Fig 6.
Correlation heat maps for pairwise anatomical connectivity between cortical sensorimotor regions of interest and seated trunk control.
Left: Correlation heat map for chronic low back pain participants (n = 32). Right: Correlation heat map for healthy control participants (n = 35). *Asterisks indicate significant correlations (p<0.05) after strict permutation threshold testing.
Fig 7.
Chord diagrams of correlations between pairwise anatomical connectivity between cortical sensorimotor regions of interest and seated trunk control in chronic low back pain participants.
Significant correlations (p<0.05) after strict permutation threshold testing are presented where negative correlations are blue and positive correlations are red. The strength of a given relationship is represented by the width and intensity of the line. Left: Correlation values for 95% confidence ellipse area (CEA) in eyes open (EO) condition. Right: Correlation values for 95% CEA in eyes closed (EC) condition.