Locomotor sequence learning in visually guided walking

Abstract

Choi JT, Jensen P, Nielsen JB. Locomotor sequence learning in visually guided walking. J Neurophysiol 115: 2014 -2020, 2016. First published February 10, 2016 doi:10.1152/jn.00938.2015.-Voluntary limb modifications must be integrated with basic walking patterns during visually guided walking. In this study 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-nonspecific 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 Ϯ 5 yr, n ϭ 20) could learn a specific sequence of step lengths over 300 training steps. Younger children (age 6 -10 yr, n ϭ 8) had lower baseline performance, but their magnitude and rate of sequence learning were the same compared with those of older children (11-16 yr, n ϭ 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 such as walking. These findings suggest that adults and children use implicit knowledge about the sequence to plan and execute leg movement during visually guided walking.human; learning; locomotion; vision; walking THE AUTOMATIC CONTROL OF WALKING is critical to our daily activities. We normally do not consciously think about walking unless we encounter novel situations where we have to make voluntary gait modifications (e.g., hiking across stepping stones). On the other hand, voluntary control of stepping patterns can become more automatic with practice (e.g., line dancing). Locomotor skills can be learned via visual cues from the environment or proprioceptive cues from the limbs during obstacle avoidance tasks (Erni and Dietz 2001;Lajoie et al. 2012). Moreover, there is some evidence that visual cue training could improve gait patterns that transfer to walking without cues in people with Parkinson's disease (Spaulding et al. 2013).The classic serial reaction-time (SRT) task, first introduced by Nissen and Bullemer (1987), may be used to assess to what an extent a motor task has become automatic. The SRT task requires subjects to rapidly respond to different spatial cues by pressing corresponding buttons as fast and accurately as possible. With practice, subjects demonstrate learning by performing faster on the repeating sequence than on random sequences. This difference can only be accounted for by sequence-specific learning, which can occur with or without explicit knowledge (Coh...

Different neural substrates for precision stepping and fast online step adjustments in youth

“…Our results imply that the ability to perform goal-directed movements with the lower limbs is mature around the age of 8 years. Similarly, Choi et al ( 2016 ) revealed stable, adult-like step accuracy on step targets in children aged 11–16 years (comparable to our sample of 9–18 years). These authors did, however, show decreasing step accuracy in younger children aged 6–10 years.…”

“…Studies illustrate an ongoing refinement of complex gait strategies after the age of 8 years during complex gait tasks such as obstacle avoidance, precision stepping, and dual-task walking. This refinement is reflected by improving gait speed and obstacle clearance (Pryde et al 1997 ; Michel et al 2010 ), the presence of adult-like muscle activations (McFadyen et al 2001 ), and more efficient foot placements (Berard and Vallis 2006 ; Choi et al 2016 ; Corporaal et al 2016 ). It has been suggested, but not established, that this extended refinement relates to ongoing neural maturation of cognitive processes underlying the control of complex gait (e.g., Pryde et al 1997 ; Choi et al 2016 ; Corporaal et al 2016 ).…”

Seeing the Errors You Feel Enhances Locomotor Performance but Not Learning

“…Indeed, other work has shown that visual feedback can drive locomotor learning mechanisms that do not require adaptation or prediction error, such as sequence learning [28]. In our study, visual feedback drove voluntary correction and not adaptation because the split-belt perturbation is mechanical (i.e., the belts move at different speeds) and the prediction error is detected through proprioception.…”

Increased central common drive to ankle plantar flexor and dorsiflexor muscles during visually guided gait

“…The treadmill speed was then determined by multiplying the subject's step length with 3.9 in order to match the cadence of 80 steps per minute between subjects (see Choi et al. ()). Prior to the visually guided walking, subjects were carefully introduced to the task.…”

“…The step length was defined as 2/3 of the leg length measured from the left greater trochanter to the left lateral malleolus. The treadmill speed was then determined by multiplying the subject's step length with 3.9 in order to match the cadence of 80 steps per minute between subjects (see Choi et al (2016)). Prior to the visually guided walking, subjects were carefully introduced to the task.…”