Perceptual-motor Interaction to Improve Bimanual Coordination After Stroke
Phase: EARLY_PHASE1
Conditions: Stroke
Sponsor: Albert Einstein Healthcare Network

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
 
 
 
 
 
Perceptual-motor Interaction to Improve Bimanual Coordination After Stroke 
NCT03755076 
Date: 6-18-2025 
 
 

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
CONSORT Flow Diagram 
 
 
Assessed for eligibility (n= 184) 
Excluded (n= 104) 
   Not meeting inclusion criteria (n= 74) 
   Declined to participate (n=21) 
   Other reasons (n= 9) 
Included (n= 79) 
Con: 29; Stroke: 50 
Enrollment 
Four perceptual cue conditions, providing distinct performance feedback in a 
counterbalanced order. 
  CONDITION 1 
  Indiscriminate 
    CONDITION 2 
  Altered Gain 
 
    CONDITION 3 
  Coordination  
 
   CONDITION 4 
Dual (Altered 
gain+coordination) 

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
Study protocol:  
Specific Aim: Determine the immediate effects of perceptual cues on bimanual 
coordination in stroke survivors. This aim was to determine the immediate effect of 
perceptual cues providing feedback about (a) between-limb coordination and (b) 
differential weighting of the two arms on spatial and temporal measures of bimanual 
coordination during a common goal bimanual reaching task.  
Hypotheses: (a) Feedback on the relative timing between arms (i.e., between limb 
coordination), provided in the form of a horizontal tilt of the virtual brick, will shorten the 
time lag and increase CCr over practice. (b) A greater weighting coefficient applied to the 
weaker arm along with feedback of relative timing between arms (i.e., both cues) may 
transiently impair temporal and spatial bimanual coordination measures but will improve 
over practice.                                                                                                                                                         
 
Rationale: Perceptual cueing has a strong effect on motor performance. The requirement 
to minimize the tilt of the brick will reduce redundancy by constraining the two arms to 
move simultaneously, thus improving the coordination between arms. In addition to the 
tilt, when each arm is differentially weighted, a greater movement of the paretic arm is 
required to move the virtual brick to the target window. However, this requires the paretic 
arm to move farther and faster than the non-paretic arm to ensure that the brick is moved 
horizontally to the target. These differential demands on each arm may impair temporal 
and spatial coordination measures early after the introduction of differential arm-weighting 
cues. However, as evident from our preliminary data, patients will improve their spatial 
and temporal coordination with more trials.  
 
Participants: A total of 184 potential participants were screened and seventy nine 
participants were included in the study. These consisted of fifty individuals with chronic (> 
6 months since stroke) hemiparesis following unilateral cortical or subcortical stroke and 
twenty-nine age-matched controls. An equal number of patients with left- and right-sided 
brain damage were recruited. The inclusion criteria were as follows: (a) ability to reach 

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
along a diagonal direction at least 80% of their arm length while fully supported on a 
frictionless surface and trunk constrained. Our previous experience suggested that this 
performance criterion will recruit a relatively large spectrum of severity from mild to 
moderate impairments (Fugl-Meyer (FM) scores 32-66). Although this excluded patients 
with more severe impairments, such as those with complete paralysis, it is now known that 
different stroke severities require distinct treatment approaches. In addition, patients with 
severe motor impairments may not be able to engage their arms in bimanual or unimanual 
activities, thus limiting the testing of coordination. Patients with very mild impairments (FM 
60-66) will be included because they may have higher-order coordination deficits due to 
lesions in brain regions crucial for planning and coordinating bimanual actions. (b) Mini-
mental scale score > 26, (c) score of 4 or above on the auditory verbal comprehension part 
of the Western Aphasia Battery to ensure intact comprehension and following commands, 
and (d) no evidence of hemispatial neglect tested by a line bisection test. (e) No 
contraindications to TMS or MRI. Attempts were made to include as many men and women 
as possible. The exclusion criteria were as follows: bilateral stroke, complete paralysis, 
basal ganglia/cerebellar stroke, pain or stiffness in the upper extremity that would interfere 
with the task, or inability to follow task instructions.  
 
Procedure: Participants were instructed to “move” a common virtual brick with both arms 
to a target window without tilting the brick within a target MT of 1.2 seconds. Participants 
completed four 60-trial blocks in pseudorandom order. Each block consisted of a distinct 
task condition depending on the nature of the perceptual cues provided. The conditions 
were: 
Condition 1: Indiscriminate: Participants transported a common virtual brick fixed in a 
no-tilt position to the target position in a pseudorandom order. The movement of the brick 
in the X and Y axis is an unweighted average of the two arm movements, that is, each arm 
contributes to 50% of the virtual bar movement (50-50 weighting). Thus, the feedback cue 
was indiscriminate (i.e., just the movement of the brick without any additional information 
about the relative time lag or differential weighting).   

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
Condition 2: Altered gain:  This was similar Condition 1 (virtual brick fixed in no-tilt), but 
the arm weighting will be such that the gain of the paretic arm was reduced. With this 
manipulation, a farther movement of the paretic arm was required to maintain its 
contribution. Thus, the only perceptual cue provided here was related to the differential 
weighting of the paretic arm. 
Condition 3: Coordination: For Condition 3, the weighting coefficients of the two arms 
were equal (i.e. 50-50); and the virtual brick tilted in the direction of the lagging arm 
proportional to the relative time lag between the arms. Thus, the only perceptual cue 
provided was the relative time lag between the arms. Operational definition of relative time 
lag: Relative time lag is different from the absolute time lag. The relative time lag is the time 
lag between the relative timings of each arm within its trajectory. To illustrate, if the left and 
right arms contribute to 70 and 30% of the brick movement, respectively, the relative time 
lag at mid-movement will be zero if the left and right arms have covered half of their 
respective trajectories. Therefore, the relative time lag is influenced by the temporal and 
spatial components of the movement of each arm. Concurrent and post-response 
feedback regarding the tilt and path of the virtual brick was provided after each trial.  
Condition 4: Dual cues: In addition to the “tilt” feedback about the relative time lag (like in 
Condition 3), each arm was differentially weighted, that is, the paretic arm had a lower gain 
(or higher weighting coefficient) than the nonparetic arm (like Condition 2). Specifically, 
based on our preliminary studies, the lower gain the paretic arm contributed to ~60-70% of 
the virtual brick movement, whereas the nonparetic arm contributed to ~30-40% of the 
virtual brick movement. Thus, in this condition, participants received both perceptual 
conditions (relative time lag and differential weighting) simultaneously.  
 
Dependent measures Coordination between the two arms was quantified by cross-
correlation between the tangential velocities of the two arms. Spatial coordination was 
characterized by the peak cross-correlation coefficient (CCr) between the tangential 
velocity profiles of the two arms. CCr values closer to 1 indicated better spatial 
coordination. Temporal coordination was quantified as the time lag at which the peak 

Perceptual-motor interaction to improve bimanual coordination after stroke  NCT03755076 
cross-correlation coefficient was obtained via cross-correlation analysis. A shorter time 
lag (closer to zero) indicated stronger temporal bimanual synchrony. A positive lag 
indicated that the paretic arm (non-dominant in the control) lagged behind the non-paretic 
arm (dominant in controls). 
 
Statistical plan: The study design included between-subject variables (stroke and control 
groups) and two within-subject variables (perceptual cue conditions: 1-4; and two time 
points: start of practice (SOP) and end of practice (EOP). Z-score (Fisher’s z)-transformed 
cross-correlation coefficients (CCrs) were used for analyses. Box-cox transformation was 
used for the time-lag data. Transformed measures of spatial and temporal coordination 
measures were analyzed using a separate 2 GROUP (stroke, controls) × 4 PERCEPTUAL 
CUE CONDITIONS (veridical, coordination, altered gain, and combined coordination+ 
altered gain feedback) × TIME (SOP, EOP) with repeated measures on the last two factors. 
The focus of this study was to compare the effects of different perceptual cues on 
individuals with stroke and age-matched neurotypical controls. Sex was used as the 
covariate. 
 
Expected results and interpretation: We expected to observe a significant group main 
effect and a significant interaction between feedback and arm weighting. When the brick is 
fixed, we expect that there will be no difference in the arm weighting conditions; when the 
brick is free to tilt, we expect that 50-50 arm weighting will result in better temporal and 
spatial coordination compared to 70-30 arm weighting. Similarly, we expected poorer 
coordination for parallel conditions compared to the mirror condition. 70-30 arm weighting 
will lead to a greater contribution of the paretic arm than the 50-50 weighting.  
 
Pitfalls and contingencies: It is likely that the tilt cue conveys spatial rather than temporal 
information. In such cases, we reiterate our instructions assisted by example templates of 
how the tilt is determined. We ensured that the participants’ understanding was clear.