Deficits in Motor Response to Avoid Sudden Obstacles During Gait in Functional Walkers Poststroke.
Deficits in Motor Response to Avoid Sudden Obstacles During Gait in Functional Walkers Poststroke.
Filed under: Rehab Centers
Neurorehabil Neural Repair. 2012 Oct 16;
van Swigchem R, van Duijnhoven HJ, den Boer J, Geurts AC, Weerdesteyn V
BACKGROUND: . Safe community ambulation requires the capacity to adapt gait to environmental changes on short notice. Reduced adaptability may contribute to an increased risk for falls. OBJECTIVE: . This study investigated gait adaptability in community-dwelling persons poststroke and sought to understand some of the mechanisms of reduced adaptability. METHODS: . Participants were 25 poststroke persons (Functional Ambulation Categories score 5) and 25 healthy controls of similar age. During treadmill walking, 30 obstacles were suddenly dropped in front of the affected leg or left leg of controls. The participants had to avoid the obstacle by either lengthening or shortening the ongoing stride. The obstacle avoidance success rates were determined. Electromyography activity of bilateral biceps femoris, rectus femoris, tibialis anterior, and gastrocnemius medialis muscles was recorded as well as concomitant knee and hip angle courses and spatial characteristics of the avoiding stride. RESULTS: . Poststroke persons demonstrated markedly decreased obstacle avoidance success rates, most prominently under time pressure. They showed normal avoidance strategies but had delayed and reduced electromyography responses, smaller joint angle deviations from unperturbed walking, and smaller horizontal margins from the foot to the obstacle. CONCLUSIONS: . Even in persons who were only mildly affected by stroke, gait adaptability may be reduced, which may place them at risk of falling. Delayed and decreased muscle responses were identified as one possible mechanism with diminished ability to adapt the length of the avoiding stride. Rehabilitation interventions could focus on these impairments.
HubMed – rehab
Functional Recovery Following Stroke: Capturing Changes in Upper-Extremity Function.
Filed under: Rehab Centers
Neurorehabil Neural Repair. 2012 Oct 16;
Simpson LA, Eng JJ
BACKGROUND: and purpose. Augmenting changes in recovery is core to the rehabilitation process following a stroke. Hence it is essential that outcome measures are able to detect change as it occurs, a property known as responsiveness. This article critically reviewed the responsiveness of functional outcome measures following stroke, specifically examining tools that captured upper-extremity (UE) functional recovery. METHODS: . A systematic search of the literature was undertaken to identify articles providing responsiveness data for 3 types of change (observed, detectable, and important). RESULTS: . Data from 68 articles for 14 UE functional outcome measures were retrieved. Larger percentage changes were required to be considered important when obtained through anchor-based methods (eg, based on patient opinion or comparative measure) compared with distribution methods (eg, statistical estimates). Larger percentage changes were required to surpass the measurement error for patient-perceived functional measures (eg, Motor Activity Log) compared with laboratory-based performance measures (eg, Action Research Arm Test). The majority of rehabilitation interventions have similar effect sizes on patient-perceived UE function and laboratory-based UE function. CONCLUSIONS: . The magnitude of important change or change that surpasses measurement error can vary substantially depending on the method of calculation. Rehabilitation treatments can affect patient perceptions of functional change as effectively as laboratory-based functional measures; however, larger sample sizes may be required to account for the larger measurement error associated with patient-perceived functional measures.
HubMed – rehab
Overcoming motor “forgetting” through reinforcement of learned actions.
Filed under: Rehab Centers
J Neurosci. 2012 Oct 17; 32(42): 14617-21
Shmuelof L, Huang VS, Haith AM, Delnicki RJ, Mazzoni P, Krakauer JW
The human motor system rapidly adapts to systematic perturbations but the adapted behavior seems to be forgotten equally rapidly. The reason for this forgetting is unclear, as is how to overcome it to promote long-term learning. Here we show that adapted behavior can be stabilized by a period of binary feedback about success and failure in the absence of vector error feedback. We examined the time course of decay after adaptation to a visuomotor rotation through a visual error-clamp condition-trials in which subjects received false visual feedback showing perfect directional performance, regardless of the movements they actually made. Exposure to this error-clamp following initial visuomotor adaptation led to a rapid reversion to baseline behavior. In contrast, exposure to binary feedback after initial adaptation turned the adapted state into a new baseline, to which subjects reverted after transient exposure to another visuomotor rotation. When both binary feedback and vector error were present, some subjects exhibited rapid decay to the original baseline, while others persisted in the new baseline. We propose that learning can be decomposed into two components-a fast-learning, fast-forgetting adaptation process that is sensitive to vector errors and insensitive to task success, and a second process driven by success that learns more slowly but is less susceptible to forgetting. These two learning systems may be recruited to different degrees across individuals. Understanding this competitive balance and exploiting the long-term retention properties of learning through reinforcement is likely to be essential for successful neuro-rehabilitation.
HubMed – rehab
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