How aging affects visuomotor adaptation and retention in a precision walking paradigm.

Motor learning is a lifelong process. However, age-related changes to musculoskeletal and sensory systems alter the relationship (or mapping) between sensory input and motor output, and thus potentially affect motor learning. Here we asked whether age affects the ability to adapt to and retain a novel visuomotor mapping learned during overground walking. We divided participants into one of three groups (n = 12 each) based on chronological age: a younger-aged group (20-39 years old); a middle-aged group (40-59 years old); and an older-aged group (60-80 years old). Participants learned a new visuomotor mapping, induced by prism lenses, during a precision walking task. We assessed retention one-week later. We did not detect significant effects of age on measures of adaptation or savings (defined as faster relearning). However, we found that older adults demonstrated reduced initial recall of the mapping, reflected by greater foot-placement error during the first adaptation trial one-week later. Additionally, we found that increased age significantly associated with reduced initial recall. Overall, our results suggest that aging does not impair adaptation and that older adults can demonstrate visuomotor savings. However, older adults require some initial context during relearning to recall the appropriate mapping.

Mobility-Related Gaze Training in Individuals With Glaucoma: A Proof-of-Concept Study.

PURPOSE: Older adults with glaucoma show inappropriate gaze strategies during routine mobility tasks. Furthermore, glaucoma is a risk factor for falling and colliding with objects when walking. However, effective interventions to rectify these strategies and prevent these adverse events are scarce. We designed a gaze training program with the goal of providing proof-of-concept that we could modify mobility-related gaze behavior in this population. METHODS: A total of 13 individuals with moderate glaucoma participated in this study. We taught participants general and task-specific gaze strategies over two 1-hour sessions. To determine the efficacy of this gaze training program, participants performed walking tasks that required accurate foot placement onto targets and circumventing obstacles before and after training. We used a mobile eye tracker to quantify gaze and a motion-capture system to quantify body movement. RESULTS: After training, we found changes in the timing between gaze shifts away from targets relative to stepping on them (P < 0.05). In the obstacle negotiation task, we found a greater range of gaze shifts early in walking trials and changes in the timing between gaze shifts away from obstacles after training (P < 0.05), each suggesting better route planning. A posttraining reduction in foot-placement error and obstacle collisions accompanied these changes (P < 0.05). CONCLUSIONS: Our results demonstrated that it is possible to modify mobility-related gaze behavior and mobility performance in older adults with glaucoma. TRANSLATIONAL RELEVANCE: This study provides proof-of-concept for a gaze training program for glaucoma. A larger, randomized controlled trial is warranted.

Adaptive Gaze Strategies to Reduce Environmental Uncertainty During a Sequential Visuomotor Behaviour.

People must decide where, when, and for how long to allocate gaze to perform different motor behaviours. However, the factors guiding gaze during these ongoing, natural behaviours are poorly understood. Gaze shifts help acquire information, suggesting that people should direct gaze to locations where environmental details most relevant to the task are uncertain. To explore this, human subjects stepped on a series of targets as they walked. We used different levels of target uncertainty, and through instruction, altered the importance of (or subjective value assigned to) foot-placement accuracy. Gaze time on targets increased with greater target uncertainty when precise foot placement was more important, and these longer gaze times associated with reduced foot-placement error. Gaze times as well as the gaze shifts to and from targets relative to stepping differed depending on the target's position in the sequence and uncertainty level. Overall, we show that gaze is allocated to reduce uncertainty about target locations, and this depends on the value of this information gain for successful task performance. Furthermore, we show that the spatial-temporal pattern of gaze to resolve uncertainty changes with the evolution of the motor behaviour, indicating a flexible strategy to plan and control movement.

Short-Term Motor Learning and Retention During Visually Guided Walking in Persons With Multiple Sclerosis.

BACKGROUND: The ability to adapt, a form of short-term motor learning, and retain this adaptation, is essential for rehabilitation and for day-to-day living. Yet little research is available on this topic in persons with multiple sclerosis (PwMS), particularly in relation to complex walking tasks. OBJECTIVE: To determine the ability of PwMS to learn and retain a novel relationship between visual input and motor output-or visuomotor map-during visually guided walking. METHODS: Nineteen PwMS and 17 healthy controls performed a precision walking task while adapting to prism lenses that altered the normal visuomotor map on 1 day, and again after a 1-week delay. The task required individuals to walk and step onto 2 targets without stopping. To quantify motor performance, we determined foot placement error relative to the targets. RESULTS: PwMS with mild disability and healthy controls attenuated foot placement error over repeated trials when exposed to the novel mapping and demonstrated a similar rate and magnitude of adaptation in the first learning session. Both groups equally retained the adaptation 1 week later, reflected by reduced foot placement error and a faster rate of error reduction in that session. CONCLUSION: PwMS can learn and retain a novel visuomotor mapping during a precision-based walking task. This suggests that PwMS with mild disability have the capacity for short-term motor learning and retention, indicating that neural plasticity is preserved.