We studied how subjects learned to make movements against unpredictable perturbations. Twelve healthy human made goal-directed reaching in the horizontal plane while holding handle of a two-joint robotic manipulator. The robot generated viscous force fields that perturbed limb perpendicular desired direction movement. amplitude (but not direction) field varied randomly from trial trial. Systems identification techniques were employed characterize adapted these random Subject performance was...

We studied the stability of changes in motor performance associated with adaptation to a novel dynamic environment during goal-directed movements dominant arm. Eleven normal, human subjects made targeted reaching horizontal plane while holding handle two-joint robotic manipulator. This robot was programmed generate viscous force field that perturbed limb perpendicular desired direction movement. Following this field, we sought determine relative role kinematic errors and criteria promoting...

People tend to make straight and smooth hand movements when reaching for an object. These trajectory features are resistant perturbation, both proprioceptive as well visual feedback may guide the adaptive updating of motor commands enforcing this regularity. How is information from two senses combined generate a coherent internal representation how arm moves? Here we show that eliminating hand-path deviations straight-line reach (constraining motion within virtual, "visual channel") prevents...

We investigated the effects of trial-to-trial, random variation in environmental forces on motor adaptation human subjects during reaching. Novel sequences dynamic environments were applied to subjects' hands by a robot. Subjects reached first “mean field” having constant gain relating force and velocity, then “noise field,” that varied randomly between reaches according normal distribution with mean identical field. The unpredictable nature noise field did not degrade as quantified final...

We examined control of the hand's trajectory (direction and shape) final equilibrium position in horizontal planar arm movements by quantifying transfer learned visuomotor rotations between two tasks that required aiming hand to same spatial targets. In a trajectory-reversal task ("slicing"), reversed direction within target returned origin. positioning ("reaching"), subjects moved held it there; cursor feedback was provided only after movement ended isolate learning from direction. asked...

The issue of how the Euclidean properties space are represented in nervous system is a main focus study visual perception, but equally relevant to motor learning. goal our experiments was investigate guide remapping coordination. Subjects wore an instrumented data glove that recorded finger motions. Signals generated by operated remotely controlled endpoint: cursor on computer monitor. subjects were instructed execute movements this endpoint with motions fingers. This required inverting...

We characterized how hemiparetic stroke survivors and neurologically intact individuals adapt reaching movements to compensate for unpredictable environmental perturbations. tested the hypotheses that like unimpaired subjects, using sensory information obtained during only most recent reliability of target acquisition decreases as degree sensorimotor impairment increases. Subjects held handle a two-joint robotic arm applied forces hand while between targets in horizontal plane. The robot...

We studied reach adaptation to a 30° visuomotor rotation determine whether augmented error feedback can promote faster and more complete motor learning. Four groups of healthy adults reached with their unseen arm visual targets surrounding central starting point. A manipulandum tracked hand motion projected cursor onto display immediately above the horizontal plane movement. For one group, deviations from ideal movement were amplified gain 2 whereas another group experienced 3.1. The third...

We developed a real-time controller for 2 degree-of-freedom robotic system using xPC Target. This was used to investigate how different methods of performance error feedback can lead faster and more complete motor learning in individuals asked compensate novel visuo-motor transformation (a 30 degree rotation). Four groups normal human subjects were reach with their unseen arm visual targets surrounding central starting location. A cursor tracking hand motion provided during each reach. For...

We previously reported that the kinematics of reaching movements reflect superimposition two separate control mechanisms specifying hand's spatial trajectory and its final equilibrium position. now asked whether brain maintains representations goals for planning hand One group subjects learned a 30 degrees visuomotor rotation about starting point while performing movement reversal task ("slicing") in which they reversed direction at one target terminated another. This required accuracy...

Prior learning of a motor skill creates memories that can facilitate or interfere with new, but related, skills. One hypothesis posits for sensorimotor task redundant degrees freedom, the nervous system learns geometric structure and improves performance by selectively operating within space. We tested this examining if transfer between two tasks depends on shared dimensionality their respective spaces. Human participants wore data glove learned to manipulate computer cursor moving fingers....

Although upper limb impairment is one of the most common deficits post-stroke and contributes substantially to diminished functional independence, many survivors receive low dosages task training in inpatient setting. This study evaluates feasibility user experience a progressive-challenge cued activity program, delivered via wearable technology, promote an rehabilitation facility (IRF) post-stroke. Participants (n=30) wore our system Souvenir, which provided vibrotactile cues prompt...

Although upper limb impairment is one of the most common deficits post-stroke and contributes substantially to diminished functional independence, many survivors receive low dosages task training in inpatient setting. This study evaluates feasibility user experience a progressive-challenge cued activity program, delivered via wearable technology, promote an rehabilitation facility (IRF) post-stroke. Participants (N = 30) wore our system Souvenir, which provided vibrotactile cues prompt...

We examined how people organize redundant kinematic control variables (finger joint configurations) while learning to make goal-directed movements of a virtual object (a cursor) within low-dimensional task space computer screen). Subjects participated in three experiments performed on separate days. Learning progressed rapidly day 1, resulting reduced target capture error and increased cursor trajectory linearity. On days 2 3, one group subjects adapted rotation the nominal map, imposed...

Background. Impaired motor control of the upper extremity after stroke may be related to lost sensory, motor, and integrative functions brain. Artificial activation sensory afferents might improve movement by adding excitatory drive sensorimotor structures. The authors evaluated effect wrist tendon vibration (TV) on paretic upper-arm stability during point-to-point planar movements. Methods. TV (70 Hz) was applied forearm musculature 10 hemiparetic patients as they made center-out arm...

Proprioception plays important roles in planning and control of limb posture movement. The impact proprioceptive deficits on motor function post-stroke has been difficult to elucidate due limitations current tests arm proprioception. Common clinical only provide ordinal assessment integrity (eg. intact, impaired or absent). We introduce a standardized, quantitative method for evaluating proprioception within the continuous, ratio scale. demonstrate approach, which is based signal detection...

Electroencephalogram coherence was measured in children with autism spectrum disorders ( ASD ) and control at baseline while watching videos of a familiar unfamiliar person reading story. Coherence between the left right hemispheres frontal, parietal, temporal‐parietal lobes (interhemispheric) frontal parietal each hemisphere (intrahemispheric). A data‐reduction technique employed to identify frequency (alpha) that yielded significant differences video conditions. Children displayed reduced...

Deficits of kinesthesia (limb position and movement sensation) commonly limit sensorimotor function its recovery after neuromotor injury. Sensory substitution technologies providing synthetic kinesthetic feedback might re-establish or enhance closed-loop control goal-directed behaviors in people with impaired kinesthesia. As a first step toward this goal, we evaluated the ability unimpaired to use vibrotactile sensory stabilization reaching tasks. Through two experiments, compared objective...

The goal of this study was to evaluate the influence wrist tendon vibration on a multijoint elbow/shoulder tracking task. We hypothesized that applied at musculature would improve upper arm performance in chronic stroke survivors through increased, Ia-afferent feedback central nervous system (CNS). To test hypothesis, 10 and 5 neurologically intact subjects grasped handle planar robot as they tracked target horizontal figure-8 pattern. A total 36 trials were completed by each subject. During...

Body–machine interfaces (BMIs) provide a non-invasive way to control devices. Vibrotactile stimulation has been used by BMIs performance feedback the user, thereby reducing visual demands. To advance goal of developing compact, multivariate vibrotactile display for BMIs, we performed two psychophysical experiments determine acuity perception across arm. The first experiment assessed vibration intensity discrimination sequentially presented stimuli within four dermatomes arm (C5, C7, C8, and...

In identical experiments in and out of a MR scanner, we recorded functional magnetic resonance imaging electromyographic correlates wrist stabilization against constant time-varying mechanical perturbations. Positioning errors were greatest while stabilizing random torques. Wrist muscle activity lagged changes joint angular velocity at latencies suggesting trans-cortical reflex action. Drift stabilized hand positions gave rise to frequent, accurately directed, corrective movements, that the...