LEGENDS FOR SUPPLEMENTARY MATERIAL
Supplementary Figure 1: Altered kinematics of the hindlimb post-Hx. Mean (±SEM)
durations of the stance phase and range of joint movements of the right (lesioned) hindlimb
indicate that 21 days post-Hx all rats show a longer stance phase, a decrease in knee and toe
joint excursions, and a concurrent increase in the ankle joint excursions (attributable to the
drag of the ipsilesional limb). Data are from 10 steps for all rats before (pre-Hx) and 21 days
post-Hx.
Supplementary Figure 2: Improved consistency of foot placement after quadrupedal
step-training. The consistency of toe (A) and ankle (B) angles during paw placement as
determined by the first principal component (PCA) is not different before and 21d post-Hx in
the QT group. In contrast, the BT and NT groups show lower consistency of toe placement
post-Hx compared to pre-Hx. The vertical alignment of the trunk during stepping determined
by the distance of the knee (C) and of the iliac crest of the pelvic bone (D) from the treadmill
in the QT and BT groups was not different from Pre-Hx and greater than in the NT group.
Values are mean (±SEM) for 10 steps. Horizontal lines above the bars indicate significant
differences among groups (P< 0.05).
Supplementary Figure 3: Quadrupedal step-training is effective in improving interhindlimb coordination. (A) Mean (±SEM) lag times between the onset of the right and left
limb contact on the stepping surface within a step during quadrupedal stepping at each time
point are shown. (B) The onset of the left and right TA EMG bursts normalized to the step
cycle duration are presented as coordinates in a phase difference diagram using basic
trigonometric functions. The position of each data point in a quadrant of the circle reflects the
phase difference between the onset of the left vs. right TA activity and the distance of each
data point from the center of the circle represents the average percentage of the step cycle
duration (represented on a scale of -1 to +1). Quantification of the phase differences between
the right and left TA activity was done using cluster analysis for group means before and 21
days post-Hx. Note the nucleated cluster of data points in pre-Hx vs. a scattered cluster postHx. (C) The phase
difference in
the
timing of limb
placement determined
electrophysiologically via cluster analysis of the phase difference between the onset of TA
EMG in the two hindlimbs for 10 consecutive steps. K-means of the clusters (centroid) that
represent the ‘average’ of the cluster distribution of all points in (B) before (open circles) and
21 days after Hx for each group (filled circles) are shown. (D) Data at 21 days post-Hx
iterated by random-sampling (boot strapping method) to yield the centroid distance over
10,000 iterations. Horizontal lines above the bars (A) and below the points (C) indicate
significant differences among groups (P< 0.05).
Supplementary Figure 4: Quadrupedal step-training improves intra-limb coordination
and limb symmetry as determined by knee-ankle angle trajectories. (A) Intralimb
coordination determined kinematically via angle-angle plots illustrates the mean right (dark
trace) and left (light trace) hindlimb knee-ankle angle trajectories. The orange triangle is an
algebraic representation of the trajectory shapes. Segment AB of the trajectory that forms an
angle with the x-axis indicates the shape of the trajectory. Maximum anti-clockwise rotation
of the right hindlimb shape trajectory (and a consequent increase in angles formed with the xaxis) reflects a change in angular phase relationships between joints within the hindlimb and
hence altered intralimb coordination during stepping. (B) Asymmetry between the two
hindlimbs is indicated by greater horizontal distances between the centers of the trajectories
for the right and left hindlimbs (centroid of triangle, maroon circles in (A)). Values are means
(±SEM) for 10 steps and the horizontal lines above the bars indicate significant differences
among groups (P< 0.05).
Supplementary Figure 5: Tracer dye injection area is similar between groups.
Histograms represent the mean (±SEM) areas of spread of the rhodamine tracer dye injection
into the right L2 spinal segment for all rats in each group.
Supplementary Video: Quadrupedal stepping before and post-Hx is shown in a
representative rat from each group. Note that the uninjured rat steps quadrupedally on the
treadmill without any support. The rat in the QT group steps similarly to an uninjured rat and
without external support to the trunk or tail. The rats in the BT and NT groups, in contrast,
step poorly and partial trunk and tail support is necessary to enable effective weight bearing
and coordination during stepping.