Astronauts are subject to sensorimotor disturbances when they enter a new gravity environment, such as the lunar or Mars surface. These disturbances can disrupt their abilities to carry out mission tasks. Previous research has shown training will lead to faster adaptation to new environments.
Dr. Jacob Bloomberg and his colleagues are developing a comprehensive training program that will enhance astronauts' ability to "learn how to learn," leading to rapid adaptation to a new gravity environment. The team has designed and is testing a unique training system comprised of a treadmill placed on a motion base facing a virtual visual scene that provides a variety of sensory challenges that serve as training modalities to enhance sensorimotor adaptability. The researchers are determining how to optimize training to maximize efficacy, efficiency and retention of the training program.
Jacob J. Bloomberg, Ph.D.
NASA Johnson Space Center
During adaptation to novel gravitational environments, sensorimotor disturbances have the potential to disrupt the ability of astronauts to perform required mission tasks. The overall goal of this project is to gain the information necessary to develop a comprehensive sensorimotor adaptability (SA) training program to facilitate rapid adaptation to novel gravitational environments.
It has been previously shown that subjects trained to adapt to varied sensorimotor challenges can adapt faster to new sensory environments that they have never experienced before. This is a process known as adaptive generalization, and it enhances the ability to “learn how to learn” to adapt to novel environments. By applying these motor learning concepts for training astronauts, we can enhance their ability to rapidly adapt their behavioral responses following a gravitational transition.
To minimize cost and demands on crew time, we have integrated SA training with existing exercise activities, namely treadmill walking. The SA training program we are developing entails manipulating the sensory conditions of treadmill exercise to systematically challenge multiple sensorimotor systems while conducting nominal exercise activities. To provide SA training we have mounted a treadmill on a six degree-of-freedom motion base to produce variation in the support surface. In addition, there is variation in visual input during walking using both a projected virtual scene that produces variation in visual flow or through goggles that distort visuomotor information.
This project is in its second year. In our first study we aimed to determine whether SA skills learned during treadmill SA training could transfer to a novel discordant sensory environment and to quantify the extent to which any training effects would be retained. Twenty subjects (10 training, 10 control) completed three, 30-minute training sessions consisting of various congruent and incongruent combinations of support surface and visual scene manipulations. Control group participants walked on the treadmill but did not receive any visual or support surface alterations.
To determine the efficacy of training, all subjects performed the Transfer/Retention Test upon completion of training. For this test, subjects were exposed to novel visual flow and support surface movement, not previously experienced during training. The Transfer/Retention Test was performed 20 minutes after the final training session. Stride frequency, auditory reaction time and heart rate data were collected during this test as measures of postural stability, dual tasking ability and anxiety, respectively. Subjects who received SA training showed less alteration in all three performance metrics compared to controls.
We conclude that subjects who received SA training adapted faster than controls when presented with a novel discordant environment because they were able to apply adaptive skills that were learned during their earlier training sessions. Importantly, the training improved performance across a number of modalities including enhanced locomotor function, increased multi-tasking capability and reduced anxiety during adaptation to novel discordant sensory information.
The Transfer Retention Test was then re-administered to both groups one week, one month, three months and six months later to examine retention of training. Trained subjects maintained their level of performance over six months.
In a second study, we investigated whether performance in a novel discordant sensory environment can be predicted based on a subject’s inherent visual dependency. To test individual visual dependency, subjects (n=10) were presented with incongruent visual flow during treadmill walking. Visual dependency was assessed by measuring the magnitude of torso translation during scene motion using video motion capture techniques. Following the visual dependency assessment, subjects were exposed to a novel combination of support surface movement and visual flow.
Subjects with greater visual dependency had increased stride frequency, reaction times and heart rates indicating that these subjects had decreased postural stability, increased anxiety and decreased ability to dual task when negotiating novel sensory discordant conditions. These data indicate that visual dependency may be a “marker” for decreased ability to adapt to novel environments. Identifying pre-flight predictors of SA can be used to develop individualized training prescriptions that target the specific needs of each crew member, thus making the training process targeted and more efficient.
The goal of our third study (currently in progress) is to determine if SA training using treadmill walking transfers to other functional tasks including manual control. In this study, subjects (n=45) are assigned to one of three groups. Subjects in the treadmill training group walk on a treadmill while wearing a series of goggles that distort visual input while viewing a virtual hallway scene thereby producing a sensorimotor adaptive challenge during treadmill exercise. Subjects in the two other groups serve as controls.
Before experiencing the training, subjects perform two operationally-oriented manual control tests (Purdue Pegboard Test, Construction Activity Test). After completing the training, all subjects (regardless of group) perform both manual control tests while wearing goggles with unique visual distortions not previously experienced by the subjects to determine if SA training has transferred from the locomotor system to the manual control system. These data will help us determine if treadmill SA training can generalize beyond locomotion. If it does transfer to other functional tasks, we will need only one type of training modality to enhance other functional tasks including those comprised of complex manual control requirements.
Jacob J. Bloomberg, Ph.D.
NASA Johnson Space Center
Sensorimotor adaptability training programs have Earthbound application in rehabilitation of patients with balance disorders and for fall prevention training among seniors. The most important factors underlying morbidity in the older adult population are injurious falls and the restriction of activity due to falls. Approximately 25-35 percent of community-dwelling persons older than 65 years fall at least once a year, and approximately 40-50 percent of fallers experience two or more falls. The outcome is that 40 percent of all nursing home admissions are due to injuries from falls. Age-related sensory changes and deterioration in ability to compensate in older adults can contribute to increased incidence of falling.
We previously conducted a study to determine if balance training using variation in visual flow during treadmill exercise improves functional mobility in healthy older adults who were experiencing age-related postural instabilities (Buccello-Stout et al. 2008). The results showed that subjects who were exposed to varied visual flow during treadmill walking significantly improved their ability to negotiate an obstacle course after training compared to another elder group who only walked on a treadmill for the same amount of time. Importantly, the training benefit was retained when subjects were tested four weeks later. This study confirms that adaptability training developed for use by astronauts can also be used to improve balance and gait performance in elder subjects and points to the general applicability of this type of training in different clinical populations.