This trial demonstrates that TAEX effectively improves cardiovascular fitness and gait in persons with chronic stroke.

Determining the approach of a moving object is a vital survival skill that depends on the brain combining information about lateral translation and motion-in-depth. Given the importance of sensing motion for obstacle avoidance, it is surprising that humans make errors, reporting an object will miss them when it is on a collision course with their head. Here we provide evidence that biases observed when participants estimate movement in depth result from the brain's use of a ''prior'' favoring slow velocity. We formulate a Bayesian model for computing 3D motion using independently estimated parameters for the shape of the visual system's slow velocity prior. We demonstrate the success of this model in accounting for human behavior in separate experiments that assess both sensitivity and bias in 3D motion estimation. Our results show that a surprising perceptual error in 3D motion perception reflects the importance of prior probabilities when estimating environmental properties.Bayes ͉ binocular disparity ͉ motion perception ͉ stereopsis H umans use visual information to respond to dangers and opportunities from a distance. This allows time to prepare motor responses before critical events occur. Expert sportsmen, for instance, make fine judgments about the flight of small, fast-moving balls before they impact with their bodies (1-3). More mundanely, adults rarely allow themselves to be hit unintentionally on the head by objects moving in 3D space. How does the brain ensure this successful behavior?To understand the mechanisms supporting motion estimation, we exploit a surprising bias: when viewing 3D motion, observers overestimate angular trajectories to report that an object will miss them when it is actually on a collision course with their head (4). This bias has been reported independently under different experimental settings involving both computer presentation (5-10) and real-world object motion (5, 11). However, given the importance of 3D motion estimation, this bias remains controversial as the general expectation is that experience-driven calibration should remove systematic errors.Much less controversial are reports that perceived motion in the fronto-parallel plane is biased under some circumstances. Specifically, low-contrast stimuli are reported to move slower than highercontrast stimuli when speeds are equivalent (12, 13). This has been accounted for by Bayesian estimation, whereby sensory evidence is combined with prior knowledge of the probability of encountering motion in the environment. In particular, it has been proposed that the visual system expects near zero net motion of the environment, and the influence of this prior expectation depends on the reliability of the available sensory evidence (14, 15): low-contrast stimuli provide less reliable information, so the brain relies more heavily on its expectation that motion will not be encountered. Here we develop a Bayesian model for the more complicated case of 3D motion estimation using independently estimated parameters of the ''velocity pr...

Background Aerobic treadmill exercise (T-EX) therapy has been shown to benefit walking and cardiorespiratory fitness in stroke survivors with chronic gait impairment even long after their stroke. The response, however, varies between individuals. Objective The purpose of this post hoc analysis of 2 randomized controlled T-EX trials was to identify predictors for therapy response. Methods In all, 52 participants received T-EX for 3 (Germany) or 6 (United States) months. Improvements in overground walking velocity (10 m/6-min walk) and fitness (peak VO2) were indicators of therapy response. Lesion location and volume were measured on T1-weighted magnetic resonance scans. Results T-EX significantly improved gait and fitness, with gains in 10-m walk tests ranging between +113% and −25% and peak VO2 between −12% and 88%. Baseline walking impairments or fitness deficits were not predictive of therapy response; 10-m walk velocity improved more in those with subcortical rather than cortical lesions and in patients with smaller lesions. Improvements in 6-minute walk velocity were greater in those with more recent strokes and left-sided lesions. No variable other than training intensity, which was different between trials, predicted fitness gains. Conclusions Despite proving overall effectiveness, the response to T-EX varies markedly between individuals. Whereas intensity of aerobic training seems to be an important predictor of gains in cardiovascular fitness, lesion size and location as well as interval between stroke onset and therapy delivery likely affect therapy response. These findings may be used to guide the timing of training and identify subgroups of patients for whom training modalities could be optimized.