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Layne, C. S.

Publications and source records attributed to Layne, C. S..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Efficacy of Stochastic Vestibular Stimulation to Improve Locomotor Performance in a Discordant Sensory Environment

Astronauts exposed to microgravity face sensorimotor challenges incurred when readapting to a gravitational environment. Sensorimotor Adaptability (SA) training has been proposed as a countermeasure to improve locomotor performance during re-adaptation, and it is suggested that the benefits of SA training may be further enhanced by improving detection of weak sensory signals via mechanisms such as stochastic resonance when a non-zero level of stochastic white noise based electrical stimulation is applied to the vestibular system (stochastic vestibular stimulation, SVS). The purpose of this study was to test the efficacy of using SVS to improve short-term adaptation in a sensory discordant environment during performance of a locomotor task.

Temple, D. R.↗
NASA NTRS2001

Effect of long-duration spaceflight on postural control during self-generated perturbations

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure (COP) motion associated with arm movement of eight subjects who experienced long-duration spaceflight (3--6 mo) aboard the Mir space station. Surface electromyography, arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions before and after spaceflight. Subjects generally displayed compromised postural control after flight, as evidenced by modified COP peak-to-peak anterior-posterior and mediolateral excursion, and pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e., when subjects were attempting to maintain upright posture in response to self-generated perturbations). These findings suggest that, although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long-duration spaceflight.

NASA Discipline Neuroscience↗
NASA NTRS1999

The Effects of Long-Duration Spaceflight on Postflight Terrestrial Locomotion

Locomotion is a complex task requiring the coordinated integration of multiple sensorimotor subsystems. This coordination is exemplified by the precise control of segmental kinematics that allows smooth progression of movement in the face of changing environmental constraints. Exposure to the microgravity environment encountered during space flight induces adaptive modification in the central processing of sensory input to produce motor responses appropriate for the prevailing environment. This inflight adaptive change in sensorimotor function is inappropriate for movement control in 1-g and leads to postflight disturbances in terrestrial locomotor function. We have previously explored the effects of short-duration (7-16 days) space flight on the control of locomotion. The goal of the present set of studies was to investigate the effects of long-duration spaceflight (3-6 months) on the control of locomotion with particular emphasis on understanding how the multiple interacting systems are adaptively modified by prolonged microgravity exposure.

Bloomberg, J. J.↗
NASA NTRS1999

Anticipatory Postural Activity During Long-Duration Space Flight

Somatosensory input has been used to modify motor output in many contexts. During space flight, the use of the lower limb musculature is much less than during activities in 1g. Consequently the neuromuscular activity of the legs is also reduced during space flight. This decrease in muscle activity contributes to muscle atrophy. Furthermore, adaptations to weightlessness contribute to posture and locomotion problems upon the return to Earth. Providing techniques to counter the negative effects of weightlessness on the neuromuscular system is an important goal, particularly during a long-duration mission. Previous work by our group has shown that lower limb neuromuscular activation that normally precedes arm movements in 1g is absent or greatly reduced during similar movements made while freefloating. However, preliminary evidence indicates that applying pressure to the feet results in enhanced neuromuscular activation during rapid arm movements performed while freefloating. This finding suggests that sensory input can be used to "drive" the motor system to increase neuromuscular functioning throughout a mission. The purpose of this investigation was to quantify the increase in neuromuscular activation resulting from the application of pressure to the feet.

Layne, C. S.↗
NASA NTRS1999

Head and Trunk Movement Control During Locomotion After Long-Duration Spaceflight

Exposure to the microgravity environment encountered during spaceflight induces adaptive alteration in sensorimotor function that leads to postflight disturbances in locomotor control. Head and trunk movement control plays a central role in maintaining gaze stability and in providing a stable reference system to permit spatial navigation in a complex and constantly varying environment. The goal of the present study was to investigate the effects of long-duration spaceflight (3-6 months) on head and trunk movement control during postflight terrestrial locomotion. Before and after spaceflight, subjects walked on a motorized treadmill while performing a challenging gaze stabilization task requiring number recognition. Head and trunk kinematic data were collected with a video-based motion analysis system. Analysis of roll, pitch and yaw head and trunk movements during treadmill walking revealed postflight alterations in head and trunk movement control in all three planes of motion. Subjects also experienced oscillopsia during postflight walking which led to impairment in performance of the number recognition task. These data indicate that exposure to long-duration space flight causes alteration in head and trunk movement control during postflight locomotion. These changes have implications for the control of gaze and maintenance of dynamic stability during walking after long-duration spaceflight.

Bloomberg, Jacob J.↗
NASA NTRS1998

Using factor analysis to identify neuromuscular synergies during treadmill walking

Neuroscientists are often interested in grouping variables to facilitate understanding of a particular phenomenon. Factor analysis is a powerful statistical technique that groups variables into conceptually meaningful clusters, but remains underutilized by neuroscience researchers presumably due to its complicated concepts and procedures. This paper illustrates an application of factor analysis to identify coordinated patterns of whole-body muscle activation during treadmill walking. Ten male subjects walked on a treadmill (6.4 km/h) for 20 s during which surface electromyographic (EMG) activity was obtained from the left side sternocleidomastoid, neck extensors, erector spinae, and right side biceps femoris, rectus femoris, tibialis anterior, and medial gastrocnemius. Factor analysis revealed 65% of the variance of seven muscles sampled aligned with two orthogonal factors, labeled 'transition control' and 'loading'. These two factors describe coordinated patterns of muscular activity across body segments that would not be evident by evaluating individual muscle patterns. The results show that factor analysis can be effectively used to explore relationships among muscle patterns across all body segments to increase understanding of the complex coordination necessary for smooth and efficient locomotion. We encourage neuroscientists to consider using factor analysis to identify coordinated patterns of neuromuscular activation that would be obscured using more traditional EMG analyses.

NASA Center JSC↗
NASA NTRS1998

The use of in-flight foot pressure as a countermeasure to neuromuscular degradation

The purpose of this study was to determine whether applying foot pressure to unrestrained subjects during space flight could enhance the neuromuscular activation associated with rapid arm movements. Four men performed unilateral arm raises while wearing--or not wearing--specially designed boots during a 81- or 115-day space flight. Arm acceleration and surface EMG were obtained from selected lower limb and trunk muscles. Pearson r coefficients were used to evaluate similarity in phasic patterns between the two in-flight conditions. In-flight data also were magnitude normalized to the mean voltage value of the muscle activation waveforms obtained during the no-foot-pressure condition to facilitate comparison of activation amplitude between the two in-flight conditions. Foot pressure enhanced neuromuscular activation and somewhat modified the phasic features of the neuromuscular activation during the arm raises.

Mir Project↗
NASA NTRS1997

Physical examination during space flight

OBJECTIVE: To develop techniques for conducting a physical examination in microgravity and to describe and document the physiologic changes noted with use of a modified basic physical examination. DESIGN: On the basis of data gathered from physical examinations on KC-135 flights, three physical variables were assessed serially in astronauts during two shuttle missions (of 8- and 10-day duration, respectively). Preflight, in-flight, and postflight examinations were conducted by trained physician-astronauts or flight surgeons, who used this modified examination. MATERIAL AND METHODS: Five male and two female crewmembers participated in the "hands-on" physical examination of all physiologic systems except the genitourinary system. Level of edema, intensity of bowel sounds, and peripheral reflexes were assessed and graded. RESULTS: This investigation identified unique elements of a physical examination performed during space flight that will assist in the development of standard methods for conducting examinations of astronauts in weightlessness. In addition, demonstrable changes induced by microgravity were noted in most physiologic systems examined. CONCLUSION: The data support the hypothesis that the microgravity examination differs from that conducted on earth or in a 1g environment. In addition, alterations in the physiologic response can be detected with use of hands-on technique. These data are invaluable in the development of optimal medical care for humans in space.

STS Shuttle Project↗
NASA NTRS1997

A review of adaptive change in musculoskeletal impedance during space flight and associated implications for postflight head movement control

We present a review of converging sources of evidence which suggest that the differences between loading histories experienced in 1-g and weightlessness are sufficient to stimulate adaptation in mechanical impedance of the musculoskeletal system. As a consequence of this adaptive change we argue that we should observe changes in the ability to attenuate force transmission through the musculoskeletal system both during and after space flight. By focusing attention on the relation between human sensorimotor activity and support surfaces, the importance of controlling mechanical energy flow through the musculoskeletal system is demonstrated. The implications of such control are discussed in light of visual-vestibular function in the specific context of head and gaze control during postflight locomotion. Evidence from locomotory biomechanics, visual-vestibular function, ergonomic evaluations of human vibration, and specific investigations of locomotion and head and gaze control after space flight, is considered.

Review, Tutorial↗
NASA NTRS1997

Neuromuscular activation patterns during treadmill walking after space flight

Astronauts adopt a variety of neuromuscular control strategies during space flight that are appropriate for locomoting in that unique environment, but are less than optimal upon return to Earth. We report here the first systematic investigation of potential adaptations in neuromuscular activity patterns associated with postflight locomotion. Astronaut-subjects were tasked with walking on a treadmill at 6.4 km/h while fixating a visual target 30 cm away from their eyes after space flights of 8-15 days. Surface electromyography was collected from selected lower limb muscles and normalized with regard to mean amplitude and temporal relation to heel strike. In general, high correlations (more than 0.80) were found between preflight and postflight activation waveforms for each muscle and each subject: however relative activation amplitude around heel strike and toe off was changed as a result of flight. The level of muscle cocontraction and activation variability, and the relationship between the phasic characteristics of the ankle musculature in preparation for toe off also were altered by space flight. Subjects also reported oscillopsia during treadmill walking after flight. These findings indicate that, after space flight, the sensory-motor system can generate neuromuscular-activation strategies that permit treadmill walking, but subtle changes in lower-limb neuromuscular activation are present that may contribute to increased lower limb kinematic variability and oscillopsia also present during postflight walking.

Flight Experiment↗
NASA NTRS1996

Lower limb kinematics during treadmill walking after space flight: implications for gaze stabilization

We examined the lower limb joint kinematics observed during pre- and postflight treadmill walking performed by seven subjects from three Space Shuttle flights flown between March 1992 and February 1994. Basic temporal characteristics of the gait patterns, such as stride time and duty cycle, showed no significant changes after flight. Evaluation of phaseplane variability across the gait cycle suggests that postflight treadmill walking is more variable than preflight, but the response throughout the course of a cycle is joint dependent and, furthermore, the changes are subject dependent. However, analysis of the phaseplane variability at the specific locomotor events of heel strike and toe off indicated statistically significant postflight increases in knee variability at the moment of heel strike and significantly higher postflight hip joint variability at the moment of toe off. Nevertheless, the observation of component-specific variability was not sufficient to cause a change in the overall lower limb joint system stability, since there was no significant change in an index used to evaluate this at both toe off and heel strike. The implications of the observed lower limb kinematics for head and gaze control during locomotion are discussed in light of a hypothesized change in the energy attenuation capacity of the musculoskeletal system in adapting to weightlessness.

NASA Discipline Number 16-10↗