Fig 1.
(A) The Kinarm Exoskeleton robotic device used to perform the Arm Position Matching (APM) Task. (B) An exemplar of the APM Task. Data taken from a stroke participant with normal performance (Task Score of 0.23). In this instance, the robot moved the participants stroke affected, left arm. Each filled symbol represents the mean position of one the nine targets where the robot moved the participant’s affected arm. The participant mirror-matched with the unaffected, right arm. The open symbols represent the mean position of each target where the participant moved their unaffected arm. Ellipsoids represent one standard deviation of variability around each matched position. For illustrative purposes the grey and solid black outlines connect the mean hand positions of the outer 8 targets for the robotically moved affected arm and participant moved arm, respectively. The data from the participant moved arm is also reflected across the midline of the participant, to make easier comparison to the target locations of the robotically moved passive arm (open symbols, outer targets connected by black dashed line). (C-E) Similar to (B), these panels demonstrate the participant’s attempts to match with the active arm (open symbols) reflected across the midline for comparison to the robotically moved hand positions (closed symbols). This has been done for illustrative purposes so the reader can make a direct visual comparison. Exemplars from stroke participants illustrate high amounts of variability (C), contraction (D) and systematic shift (E). It should be noted that while panel D) displays a participant with high amounts of contraction, it is also possible to observe examples of expansion of the workspace.
Table 1.
White matter tracts.
Fig 2.
(A) Lesion overlap map for all 203 participants. Lesions presented in neurologic convention. Numbers above (top) and below (bottom) each slice indicate the axial MNI coordinate. (B) Mean Arm Position Matching (APM) Task Scores for the left hemisphere lesion group (n = 85) and right hemisphere lesion group (n = 118). Open circles are individual data points for each participant. Black bars indicate the standard deviation around the mean for each group.
Table 2.
Participant demographics.
Fig 3.
Multivariate regression results.
Coefficient estimates and 95% confidence intervals for white matter tract lesion load (green), lesion side (black) and grey matter lesion volume (blue). Coefficients are only displayed for the white matter tracts where significant relationships occurred between the tract lesion load and Arm Position Matching (APM) Task Scores. * indicates a significant coefficient estimate at a 5% false discovery rate. SLF = Superior Longitudinal Fasciculus.
Table 3.
Principal component regression results.
Table 4.
Principal component analysis loadings.
Fig 4.
Disconnectome analysis results.
Voxels with a greater probability of disconnection in participants with Arm Position Matching (APM) Task impairments compared to participants without APM Task impairments. Voxels in green are significant at p<0.05. Voxels in blue are significant at a higher statistical peak of p<0.001. (A) Axial view. Images are presented in neurological convention. Numbers above (top) and below (bottom) each slice indicate the axial MNI coordinate. (B) Sagittal view. Right and left hemisphere are shown. Numbers above (top) and below (bottom) each slice indicate the sagittal MNI coordinate. Structures where disconnection was associated with APM task impairments include: Medial Lemniscus, Cerebral Peduncles, Internal Capsule, Corona Radiata, S1 white matter, Corpus Callosum, Arcuate Fasciculus, SLF II, SLF III, IFOF, External Capsule and Optic Radiations.
Fig 5.
White matter network in APM tasks.
(A) White matter tracts connecting cortical regions previously implicated in proprioceptive tasks, in particular, Arm Position Matching (APM) tasks. White matter tracts include: Superior Longitudinal Fasciculus II (SLF II; Purple), Superior Longitudinal Fasciculus III (SLF III; Light Blue), Arcuate Fasciculus Long Segment (Dark Blue), Arcuate Fasciculus Anterior Segment (Yellow), and Fronto Insular Tract 5 (Dark Green). (B) Alternative white matter tracts, implicated in APM task impairments, as observed by disconnectome analysis. White matter tracts include: Posterior Corpus Callosum (Green/Blue), Inferior Fronto Occipital Fasciculus (IFOF; Yellow), Optic Radiations (Orange) and, Inferior Longitudinal Fasciculus (ILF; Light Green).