Implications of Intra-Individual Variability in Motor Performance on Functional Mobility in Stroke Survivors

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation Science

Background:

• Stroke commonly causes motor impairments affecting functional mobility.
• Traditional assessments focus on average motor performance, overlooking increased variability in aging and disease.
• Intra-individual variability (IIV) in behavior predicts functional decline, but its role post-stroke is unstudied.

Purpose of the Study:

• To quantify the effect of stroke on IIV in motor performance.
• To determine the contribution of IIV and mean motor performance to functional mobility post-stroke.

Main Methods:

• Twenty stroke survivors and 20 controls performed 30 trials of a goal-directed ankle movement task.
• Measured mean endpoint error and IIV (within-person standard deviation).
• Assessed functional mobility via postural control (sway area) and a driving simulator braking response time.

Main Results:

• Stroke participants demonstrated significantly higher mean endpoint error and greater IIV compared to controls.
• While sway area did not differ, stroke survivors showed increased braking response time.
• In stroke survivors, IIV significantly predicted sway area and braking response time, with mean error adding no further explanatory power.

Conclusions:

• Stroke impairs the consistency of precise motor task execution.
• IIV in motor performance is a significant predictor of postural control and braking response time after stroke.
• IIV may serve as a key indicator of vulnerability and a crucial target for stroke rehabilitation strategies.