Julia receives NSF CAREER Award (“Adaptation and learning processes in human locomotion”).
The NSF CAREER program provides 5 year awards to tenure-track Assistant Professors to support outstanding research projects and career development activities, including education and outreach initiatives. Read the full abstract.
The lab enjoyed hosting 15 students as part of the Eureka! at UMass Amherst summer program.
Workshop Organizers:
Julia Choi, Assistant Professor of Kinesiology
Dan Gregory, Kinesiology PhD student
Gabriela Borin, Kinesiology PhD student
Jan Stenum, Kinesiology PhD student
Participants:
15 Eureka! 8th graders (Rookies)
Program:
The interactive workshop included four activities designed to show students some basic principles of human motor control. In one activity, students recorded electricity from their muscles while they squeezed a hand gripper as hard as they can for as long as they can. In another activity, they tried to convince another student that a rubber hand was his/her own by putting it on a table in front of them while stroking it in the same way as his/her real hand (known as the “rubber hand illusion”). In a third activity, students learned how our brains need to adapt, by trying to trace the diagram of a star while looking at his/her hand only as a reflection in the mirror. Finally, students experienced how the brain learns from recognizing mistakes, while throwing balls at a target with prime goggles.
Brian Kim (left), Lia Gizzi (center) and Lazar Jankovic (right) presenting an e-poster on “Retention of Locomotor Learning following Exposure to Sensorimotor Variability” at the Massachusetts Undergraduate Research Conference (April 2017).
Journal of Physiology (OI: 10.1113/JP271996
Error signals driving locomotor adaptation: Cutaneous feedback from the foot is used to adapt movement during perturbed walking
Julia T Choi 1,2, Peter Jensen 2, Jens Bo Nielsen 2 and Laurent J Bouyer3
1 Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
2 Neural Control of Movement Research Group, Department of Neuroscience and Pharmacology & Department of Nutrition, Exercise and Sport, University of Copenhagen, Denmark
3 Department of Rehabilitation, Université Laval & Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec City, Canada
Locomotor patterns must be adapted to external forces encountered during daily activities. The contribution of different sensory inputs to detecting perturbations and adapting movements during walking is unclear. Here we examined the role of cutaneous feedback in adapting walking patterns to force perturbations. Forces were applied to the ankle joint during the early swing phase using an electrohydraulic ankle-foot orthosis. Repetitive 80 Hz electrical stimulation was applied to disrupt cutaneous feedback from the superficial peroneal nerve (foot dorsum) and medial plantar nerve (foot sole) during walking (Choi et al. 2013). Sensory tests were performed to measure cutaneous touch threshold and perceptual threshold of force perturbations. Ankle movement were measured while subjects walked on the treadmill over three periods: baseline (1 min), adaptation (1 min) and post-adaptation (3 min). Subjects (n = 10) showed increased touch thresholds measured with Von Frey monofilaments and increased force perception thresholds with stimulation. Stimulation reduced the magnitude of walking adaptation to force perturbation. In addition, we compared the effects of interrupting cutaneous feedback using anaesthesia (n = 5) instead of repetitive nerve stimulation. Foot anaesthesia reduced ankle adaptation to external force perturbations during walking. Our results suggest that cutaneous input plays a role in force perception, and may contribute to the ‘error’ signal involved in driving walking adaptation when there is a mismatch between expected and actual force.
Locomotor sequence learning in visually guided walking
Julia T Choi 1,2, Peter Jensen 2 and Jens Bo Nielsen 2
1 Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts
2 Neural Control of Movement Research Group, Department of Neuroscience and Pharmacology & Department of Nutrition, Exercise and Sport, University of Copenhagen, Denmark
Voluntary limb modifications must be integrated with basic walking patterns during visually guided walking. Here we tested whether voluntary gait modifications can become more automatic with practice. We challenged walking control by presenting visual stepping targets that instructed subjects to modify step length from one trial to the next. Our sequence learning paradigm is derived from the serial reaction-time (SRT) task that has been used in upper limb studies. Both random and ordered sequences of step lengths were used to measure sequence-specific and sequence non-specific learning during walking. In addition, we determined how age (i.e., healthy young adults vs. children) and biomechanical factors (i.e., walking speed) affected the rate and magnitude of locomotor sequence learning. The results showed that healthy young adults (age 24 ± 5 years, N = 20) could learn a specific sequence of step lengths over 300 training steps. Younger children (age 6-10 years, N = 8) have lower baseline performance, but their magnitude and rate of sequence learning was the same compared to older children (11-16 years, N = 10) and healthy adults. In addition, learning capacity may be more limited at faster walking speeds. To our knowledge, this is the first study to demonstrate that spatial sequence learning can be integrated with a highly automatic task like walking. These findings suggest that adults and children use implicit knowledge about the sequence to plan and execute leg movement during visually guided walking.
39th Annual Meeting of the American Society of Biomechanics (August 2015)
Walk-run transitions are dependent on interlimb coupling
Jan Stenum and Julia T. Choi
Department of Kinesiology, University of Massachusetts, Amherst MA
Walk-run transition in adult humans has been studied during forward gaits. However, it is unknown how contralateral leg movement affects walk-run transitions. We examined walk-run transitions on a split-belt treadmill where the speed and direction of each belt can be controlled independently. We hypothesize that walk-run transitions are dependent on contralateral leg movements. A split-belt treadmill was used to test 4 different gait conditions: forward, split-belt (i.e., constant speed difference of 0.5 m/s between belts), hybrid (i.e., left leg moved backward and right leg moved forward) and backwards. Here we define preferred walk-run transition speed as the speed where a subject is equally likely to choose walk and run. We found that walk-run transition occurred at different speeds across four conditions. On average, subjects transitioned at 2.00 ± 0.20 m/s in the forward condition. When one leg moved faster than the other in the split condition, the transition speed on the fast leg increased to 2.36 ± 0.20 m/s. The transition speed was 1.47 ± 0.15 m/s in the backward condition. When one leg walked forward, and one backward in the hybrid condition, both legs transitioned to running together at a lower speed. The average walk-to-run transition speed in hybrid locomotion was 1.17 ± 0.16 m/s. We did not observe walking on one leg, and running on the other leg during hybrid locomotion for the tested speed combinations. In sum, walk-run transition speed is dependent on interlimb speed and direction differences. To our knowledge, this is the first study to investigate the effects of interlimb coupling on human walk-run transitions.
Cerebral Cortex 2015 Jul;25(7):1981-6.
Disruption of Locomotor Adaptation with Repetitive Transcranial Magnetic Stimulation Over the Motor Cortex
Julia T. Choi1,3, Laurent J. Bouyer2 and Jens Bo Nielsen3
1University of Copenhagen, Denmark, 2Université Laval and Center for Interdisciplinary Research in Rehabilitation and Social Integration, Québec City, Canada, and 3 University of Massachusetts Amherst, Amherst, MA, USA
Locomotor patterns are adapted on a trial-and-error basis to account for predictable dynamics. Once a walking pattern is adapted, the new calibration is stored and must be actively de-adapted. Here, we tested the hypothesis that storage of newly acquired ankle adaptation in walking is dependent on corticospinal mechanisms. Subjects were exposed to an elastic force that resisted ankle dorsiflexion during treadmill walking. Ankle movement was adapted in <30 strides, leading to after-effects on removal of the force. We used a crossover design to study the effects of repetitive transcranial magnetic stimulation (TMS) over the primary motor cortex (M1), compared with normal adaptation without TMS. In addition, we tested the effects of TMS over the primary sensory cortex (S1) and premotor cortex (PMC) during adaptation. We found that M1 TMS, but not S1 TMS and PMC TMS, reduced the size of ankle dorsiflexion after-effects. The results suggest that suprathreshold M1 TMS disrupted the initial processes underlying locomotor adaptation. These results are consistent with the hypothesis that corticospinal mechanisms underlie storage of ankle adaptation in walking.
Annual Massachusetts Statewide Undergraduate Research Conference (April 2015)
Gait Adaptation on a Portable and Passive Split-Belt Treadmill
Brian J. Young1, Frank Sup1,2 and Julia T. Choi1
Departments of 1Kinesiology and 2Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA
Walking requires precise coordination of movement between two legs. Interlimb coordination is often disrupted after damage to the central nervous system (e.g., stroke), resulting in walking patterns that are slowed, asymmetric and inefficient. Previous studies have shown that training with powered split-belt treadmills can lead to a more symmetric walking pattern post-adaptation in stroke subjects. The focus of this study is to test a novel gait training platform (1st generation passive split-belt treadmill) that could drive adaptation of walking symmetry. We examined healthy adults (18-40 yrs old) walking on a passive split-belt treadmill (no motors to drive the belt). The adaptation phase on the passive split-belt treadmill lasted for 5 minutes. To evaluate the presence of after-effects, participants walked over-ground before and after the adaptation phase on the passive split- belt treadmill. Motion capture, electromyography, and force platform data were recorded in all trials. Adaptation was measured by changes in spatial and temporal gait parameters (e.g., step length, stance time, swing time), joint kinematics (e.g., hip, knee, ankle angle) and leg muscle activations (e.g., EMG). The results will inform about the potential for using the passive split-belt treadmill as a rehabilitation tool. The passive split-belt would be a more affordable option compared to a powered split-belt treadmill. Having access to rehabilitation in the home is important and would allow patients to continue training for longer periods of time and maximize gait improvements.
Baby split-belt treadmill was born December 4, 2014. 60 lbs. 5 ft.
Many thanks to the delivery team (Erin Carey, Jeffrey Florek, Nicholas Lake, Eric Murray, Subhash Gandhi Vallala) and Prof. Frank Sup.
