No abstract

Tyrell CM, Helm E, Reisman DS. Learning the spatial features of a locomotor task is slowed after stroke. J Neurophysiol 112: 480 -489, 2014. First published April 30, 2014 doi:10.1152/jn.00486.2013The capacity for humans to learn a new walking pattern has been explored with a split-belt treadmill during single sessions of adaptation, but the split-belt treadmill can also be used to study longer-term motor learning. Although the literature provides some information about motor learning after stroke, existing studies have primarily involved the upper extremity and the results are mixed. The purpose of this study was to characterize learning of a novel locomotor task in stroke survivors. We hypothesized that the presence of neurological dysfunction from stroke would result in slower learning of a locomotor task and decreased retention of what was learned and that these deficits would be related to level of sensorimotor impairment. Sixteen participants with stroke and sixteen neurologically intact participants walked on a split-belt treadmill for 15 min on 5 consecutive days and during a retention test.Step length and limb phase were measured to capture learning of the spatial and temporal aspects of walking. Learning the spatial pattern of split-belt treadmill walking was slowed after stroke compared with neurologically intact subjects, whereas there were no differences between these two groups in learning the temporal pattern. During the retention test, poststroke participants demonstrated equal retention of the split-belt treadmill walking pattern compared with those who were neurologically intact. The results suggest that although stroke survivors are slower to learn a new spatial pattern of gait, if given sufficient time they are able to do so to the same extent as those who are neurologically intact. stroke; locomotion; learning; adaptation MOTOR LEARNING is traditionally defined as a persistent change in a movement that occurs over long-term practice and experience and that results in stable performance (Schmidt 1988;Schmidt and Wrisberg 2000). The process of learning begins with exposure to the task, followed by consolidation, which is a set of processes that involve changes in the central nervous system leading to a long-term memory that is resistant to disruption or interference by other motor activity (Krakauer and Shadmehr 2006;Stickgold and Walker 2007). These processes ultimately lead to the ability to recall the newly learned motor skill in the appropriate context or environment.The capacity for humans to learn a new walking pattern has been explored with a split-belt treadmill (Malone et al. 2011) and a rotating treadmill (Earhart et al. 2001). During walking on a rotating treadmill, subjects adapt their walking pattern while walking in place on the perimeter of a rotating disk. After ϳ30 min of exposure, when the subjects are blindfolded and asked to walk under normal conditions they demonstrate an involuntary and significant curvature of their walking trajectory. The split-belt treadmill is a trea...

Brain-derived neurotrophic factor (BDNF) has been directly related to exercise-enhanced motor performance in the neurologically injured animal model; however literature concerning the role of BDNF in the enhancement of motor learning in the human population is limited. Previous studies in healthy subjects have examined the relationship between intensity of an acute bout of exercise, increases in peripheral BDNF and motor learning of a simple isometric upper extremity task. The current study examined the role of high intensity exercise on upregulation of peripheral BDNF levels as well as the role of high intensity exercise in mediation of motor skill performance and retention of a novel locomotor task in neurologically intact adults. In addition, the impact of a single nucleotide polymorphism in the BDNF gene (Val66Met) in moderating the relationship between exercise and motor learning was explored. It was hypothesized that participation in high intensity exercise prior to practicing a novel walking task (split-belt treadmill walking) would elicit increases in peripheral BDNF as well as promote an increased rate and magnitude of within session learning and retention on a second day of exposure to the walking task. Within session learning and retention would be moderated by the presence or absence of Val66Met polymorphism. Fifty-four neurologically intact participants participated in two sessions of split-belt treadmill walking. Step length and limb phase were measured to assess learning of spatial and temporal parameters of walking. Serum BDNF was collected prior to and immediately following either high intensity exercise or 5 minutes of quiet rest. The results demonstrated that high intensity exercise provides limited additional benefit to learning of a novel locomotor pattern in neurologically intact adults, despite increases in circulating BDNF. In addition, presence of a single nucleotide polymorphism on the BDNF gene did not moderate the magnitude of serum BDNF increases with high intensity exercise, nor did it moderate the relationship between high intensity exercise and locomotor learning.

Background and Purpose In rehabilitation, examining how variables change over time can help to define the minimal number of training sessions required to produce a desired change. The purpose of this study was to identify the time course of changes in gait biomechanics and walking function in persons with chronic stroke. Methods Thirteen persons > 6 months post-stroke participated in 12 weeks of fast treadmill training combined with plantar- and dorsi-flexor muscle functional electrical stimulation (FastFES). All participants completed testing before the start of intervention, after 4, 8 and 12 weeks of FastFES locomotor training. Results Peak limb paretic propulsion, paretic limb propulsive integral, peak paretic limb knee flexion, (p<0.05 for all) and peak paretic trailing limb angle (p<0.01) improved from pre-training to 4 weeks but not between 4 and 12 weeks. Self-selected walking speed and 6-minute walk test distance improved from pre-training to 4 weeks and from 4 to 12 weeks (p<0.01 and p<0.05, respectively for both). Timed Up & Go test time did not improve between pre-training and 4 weeks, but improved by 12 weeks (p=0.24 and p<0.01, respectively). Discussion and Conclusions The results demonstrate that walking function improves with a different time course compared to gait biomechanics in response to a locomotor training intervention in persons with chronic stroke. Thirty-six training sessions were necessary to achieve an increase in walking speed that exceeded the MCID. These finding should be considered when designing locomotor training interventions after stroke. Video Abstract available (see Video, Supplemental Digital Content 1) for more insights from the authors.