Locomotor Experience Research Articles

Postural Stability and the Dynamics of Locomotor-Respiratory Coordination

1612 Much of the research on human locomotor-respiratory coordination has focused on synchronization or entrainment between these systems (Bramble & Carrier, 1983) with little agreement as to the extent to which entrainment occurs and what factors affect the level of entrainment. Using a nonlinear dynamics approach to the study of locomotorrespiratory coupling, we have recently shown that locomotor experience or running training does not change the synchronization or coupling strength of this coordination, but rather how these two systems adapt to changes in speed of locomotion (McDermott et al., 2003). Recent research on quiet stance also suggests that stabilizing the upper body may be an important coupling factor between the respiratory system and locomotory rhythms. The respiratory musculature not only regulates intrathoracic volume for respiration but also regulates intra-abdominal pressure for trunk stabilization (Hodges and Gandevia, 2000). Additionally, when respiratory drive is increased by induced hypercapnia, the respiratory musculature ceases to contribute to postural stabilization (Hodges et al., 2001). In this sense, increased respiratory drive acts to decouple the respiratory rhythm from the movement rhythm. This dual task has not been investigated as a coupling mechanism between locomotion and respiration, nor has the integration of locomotory and respiratory rhythms been considered in the study of gait stability. PURPOSE: To examine the integration of respiration and upper body stability control during walking in a group of healthy, young subjects by challenging both systems. METHODS: Four, 5-minute experimental conditions consisted of walking at preferred speed under: 1) normal postural and ventilation requirements, 2) challenged posture, normal ventilation, 3) normal posture, challenged ventilation, and 4) challenged posture, challenged ventilation. Posture was challenged by turning the trunk laterally to 45° using a laser and target. Ventilation was challenged by induced hypercapnia accomplished by increasing the dead space through which the subject breathed by 1150 ml. Results of how respiration and upper body control react individually and coordinatively will be reported. Implications of these results for locomotor-respiratory coordination and postural control during locomotion will be discussed in the context of aging.

Stability in young infants' discrimination of optic flow.

Although considerable progress has been made in understanding how adults perceive their direction of self-motion, or heading, from optic flow, little is known about how these perceptual processes develop in infants. In 3 experiments, the authors explored how well 3- to 6-month-old infants could discriminate between optic flow patterns that simulated changes in heading direction. The results suggest that (a) prior to the onset of locomotion, the majority of infants discriminate between optic flow displays that simulate only large (> 22 deg.) changes in heading, (b) there is minimal development in sensitivity between 3 and 6 months, and (c) optic flow alone is sufficient for infants to discriminate heading. These data suggest that spatial abilities associated with the dorsal visual stream undergo prolonged postnatal development and may depend on locomotor experience.

Posthatching locomotor experience alters locomotor development in chicks.

We have previously demonstrated that, even though chicks are very precocial and can locomote within hours of hatching, they require a period of time to develop a mature stable walk. As an example, 1- to 2-day-old animals move with disproportionately small stride lengths compared with 10- to 14-day-old animals. The purpose of this study was to determine whether the maturation of walking, including the development of a mature stride length, depends on locomotor experience. We also investigated the development and experience-dependence nature of head bobbing, an optokinetic behavior that occurs during walking in birds. Chicks were randomly assigned to one of three groups receiving either increased locomotor experience (i.e., treadmill exercise), decreased locomotor experience (i.e., decreased housing space), or no alteration in locomotor experience. To assess the dependence of locomotor maturation on N-methyl-D-aspartate (NMDA)-type glutamate receptors, animals in each group were either given an NMDA antagonist (MK-801, 1 mg/kg intramuscularly daily) or saline control. Locomotor characteristics (stride length, leg support durations, horizontal head excursions) were quantified from videotaped recordings of chicks walking overground unrestrained on posthatching days 1, 2, 4, 6, 8, and 10. Animals subject to exercise restriction for at least 6 days moved with shortened stride lengths compared with age-matched treadmill-exercised or control animals, a change that was maintained for the duration of the study. NMDA antagonism also resulted in shortened stride lengths. Head bobbing behavior matured during the same posthatching time period. The rate of this maturation was also decreased by exercise restriction. Thus locomotor experience is required for normal development of locomotor behavior, even in very precocial animals. These results are discussed in terms of the possible neuroanatomical and neurophysiological mechanisms underlying experience- and activity-dependent changes during motor development.

Spatial Cognition in Young Children With Spinal Muscular Atrophy

Success in visuospatial tasks has often been demonstrated in teenagers with spinal muscular atrophy (SMA). However, what has been tested in these studies, with the Wechsler Intelligence Scale for Children-Revised (Wechsler, 1974) performance scale, does not deal with the spatial capacities that co-occur with the advent of self-produced locomotion. Indeed, various studies have shown that occurrence of locomotion in infancy is correlated with the development of visuospatial cognitive competencies, suggesting that locomotor experience might play a central role in spatial development, especially in the realm of manual search for hidden objects. It is thus of interest to assess spatial search skills in SMA young children suffering total deprivation of locomotor experience. Twelve Type-2 SMA children with a mean age of 30 months were compared with controls with respect to their spatial search skills in a memory-for-locations task. In this search task, hiding containers were rotated 180° before search was permitted. The performance obtained with the SMA group did not differ from that obtained in the healthy control group. SMA patients searched correctly for a hidden object in the 3-choice search task. Locomotor impairment does not appear to be a key risk factor for dramatic slowing down or deviation in the development of spatial search skills, as assumed by some authors. Further research is needed to identify the alternative pathways to normal spatial development that are used by SMA young children.

The flip side of perception–action coupling: Locomotor experience and the ontogeny of visual–postural coupling

The possible role of motor development on psychological function is once again a topic of great theoretical and practical importance. The revival of this issue has stemmed from a different approach to the topic, away from Gesell's interest in the long-term prediction of psychological functions from early motoric assessments, toward an attempt to understand how the acquisition of motor skills orchestrates psychological changes. This paper describes how the acquisition of one motor skill, prone locomotion, has been linked to developmental changes in an infant's ability to regulate posture based on information available in patterns of optic flow. It is argued that the onset of prone locomotion presses the infant to differentiate spatially delimited regions of optic flow to effectively and efficiently control the important subtasks nested within the larger task of locomotion, namely, steering, attending to the surface of support, and maintaining postural control. Following this argument, a research program is described that aims to determine if locomotor experience is causally linked to improvements in the ability to functionalize peripheral optic flow for postural control or whether locomotor experience is merely a maturational forecaster of such improvements. Finally, a hypothesis is put forward that links the emergence of wariness of heights to infants' ability to regulate posture on the basis of peripheral optic flow. The paper's overarching theoretical point is the principle of probabilistic epigenesis, which states that one developmental acquisition produces experiences that bring about a host of new developmental changes in the same and different domains.

Development of Lower Extremity Kinetics for Balance Control in Infants and Young Children

Developmental changes in the kinematics and kinetics underlying balance control were studied in 61 children, 9 months to 10 years of age. The children were classified according to developmental milestones as standers; new, intermediate, and advanced walkers; runners-jumpers; hoppers; gallopers; and skippers. The children experienced support-surface translations of varying size and speed. Children with greater locomotor experience withstood larger balance threats without collapsing or stepping. Analyses of scaled trials (perturbations normalized in size to foot length and center of gravity height) revealed that improvement in balance was not related to initial configuration parameters surrounding the task (degree of crouch or lean). Children with advanced locomotor skills had faster recovery times and relatively larger muscle torques than children with less experience. Relative torque-time histories of the more experienced children began to match the adult response to similar perturbations. With increased experience and changing muscle torque regulatory abilities, balance skills became more robust.

Travel Broadens the Mind.

The onset of locomotion heralds one of the major life transitions in early development and involves a pervasive set of changes in perception, spatial cognition, and social and emotional development. Through a synthesis of published and hitherto unpublished findings, gathered from a number of converging research designs and methods, this article provides a comprehensive review and reanalysis of the consequences of self-produced locomotor experience. Specifically, we focus on the role of locomotor experience in changes in social and emotional development, referential gestural communication, wariness of heights, the perception of self-motion, distance perception, spatial search, and spatial coding strategies. Our analysis reveals new insights into the specific processes by which locomotor experience brings about psychological changes. We elaborate these processes and provide new predictions about previously unsuspected links between locomotor experience and psychological function. The research we describe is relevant to our broad understanding of the developmental process, particularly as it pertains to developmental transitions. Although acknowledging the role of genetically mediated developmental changes, our viewpoint is a transactional one in which a single acquisition, in this case the onset of locomotion, sets in motion a family of experiences and processes that in turn mobilize both broad-based and context-specific psychological reorganizations. We conclude that, in infancy, the onset of locomotor experience brings about widespread consequences, and after infancy, can be responsible for an enduring role in development by maintaining and updating existing skills.

Walking skill versus walking experience as a predictor of barrier crossing in toddlers

The aim of this study was to examine the roles of body size parameters, walking skill, and locomotor experience in determining the abilities of 14-, 18-, 24-, and 30-month-old toddlers to cross a barrier varying in height. Thresholds for barrier crossing were measured using a modified psychophysical staircase procedure, walking skill was assessed using a footprint analysis of gait, and locomotor experience via parental report. Overall, older children surpassed younger children in measures of body size, walking skill, locomotor experience, and crossing thresholds. Analyses relating the various body size, skill, and experiential parameters to crossing thresholds revealed that, replicating earlier findings, barrier crossing was most strongly related to walking experience. These findings are discussed in terms of the limitations of different forms of skill assessment as predictors of visually guided locomotor ability.

Locomotion improves children's spatial search: a meta-analytic review.

This meta-analysis quantitatively summarized the developmental influence and the effects of locomotor experience as well as the benefits of locomotor practice, locomotor assistance, and active searching patterns on children's search performance. Based on specific criteria, a search of a database and reference lists identified 19 studies, including 1,029 children (510 boys and 519 girls) from 4 to 144 months of age. Outcome measures of spatial performance were converted to 83 effect sizes that reflected the effects of specific experimental characteristics. Analyses of variance indicated that with older children, locomotor activities are more important to their spatial searching. Locomotor status, searching patterns, locomotor assistance, test conditions, and test reliability were identified as moderator variables. In addition, locomotor training significantly improved children's spatial search. The results supported the hypothesis that children's development of spatial search skills is influenced by locomotor experience.

Individual differences in object permanence performance at 8 months: Locomotor experience and brain electrical activity

This work was designed to investigate individual differences in hands-and-knees crawling and frontal brain electrical activity with respect to object permanence performance in 76 eight-month-old infants. Four groups of infants (one prelocomotor and 3 with varying lengths of hands-and-knees crawling experience) were tested on an object permanence scale in a research design similar to that used by Kermoian and Campos (1988). In addition, baseline EEG was recorded and used as an indicator of brain development, as in the Bell and Fox (1992) longitudinal study. Individual differences in frontal and occipital EEG power and in locomotor experience were associated with performance on the object permanence task. Infants successful at A-not-B exhibited greater frontal EEG power and greater occipital EEG power than unsuccessful infants. In contrast to Kermoian and Campos (1988), who noted that long-term crawling experience was associated with higher performance on an object permanence scale, infants in this study with any amount of hands and knees crawling experience performed at a higher level on the object permanence scale than prelocomotor infants. There was no interaction among brain electrical activity, locomotor experience, and object permanence performance. These data highlight the value of electrophysiological research and the need for a brain-behavior model of object permanence performance that incorporates both electrophysiological and behavioral factors.

Individual differences in object permanence performance at 8 months: Locomotor experience and brain electrical activity

Individual differences in object permanence performance at 8 months: Locomotor experience and brain electrical activity

Learning in the Development of Infant Locomotion

Infants master crawling and walking in an environment filled with varied and unfamiliar surfaces. At the same time, infants' bodies and skills continually change. The changing demands of everyday locomotion require infants to adapt locomotion to the properties of the terrain and to their own physical abilities. This Monograph examines how infants acquire adaptive locomotion in a novel task--going up and down slopes. Infants were tested longitudinally from their first week of crawling until several weeks after they began walking. Everyday locomotor experience played a central role in adaptive responding. Over weeks of crawling, infants' judgments became increasingly accurate, and exploration became increasingly efficient. There was no transfer over the transition from crawling to walking. Instead, infants learned, all over again, how to cope with slopes from an upright position. Findings indicate that learning generalized from everyday experience traveling over flat surfaces at home but that learning was specific to infants' typical method of locomotion and vantage point. Moreover, learning was not the result of simple associations between a particular locomotor response and a particular slope. Rather, infants learned to gauge their abilities on-line as they encountered each hill at the start of the trial. Change in locomotor responses and exploratory movements revealed a process of differentiation and selection spurred by changes in infants' everyday experience, body dimensions, and locomotor proficiency on flat ground.

Effects of limitations on the use of some visual and kinaesthetic information in spatial mapping during exploration in the rat.

The purpose of this experiment was to study the effects of limiting visual and/or locomotor access to a part of the environment in the building up of a spatial representation of the whole space. During five sessions, rats were allowed to explore separately and successively the two halves (subspaces) of a circular open field containing four objects. During exploration of each half, continuous or discontinuous locomotor and/or visual access to the other half was provided by using opaque or transparent partitions, with or without doors. Once habituation was complete, the partition was removed for some subjects but remained for others. The locomotor and exploratory reactions to this removal were recorded. Whatever their locomotor experience (continuous or discontinuous), rats that had a discontinuous visual experience between the subspaces displayed a renewal of exploratory activity, whereas the rats that had received a continuous visual experience did not re-explore the objects. This result suggests that continuous visual access to the whole space is necessary for the construction of an overall representation. Furthermore, continuous locomotor activity does not seem to compensate for the discontinuity of visual information.

The relation between locomotor experience and object search skills at 8.5 months of age

The relation between locomotor experience and object search skills at 8.5 months of age

Predicting object permanence performance at 8 months of age: The contributions of frontal EEG and locomotor experience

Previous literature suggests that attention processes such as sustained attention would constitute a developmental foundation for the self-regulatory functions executive functioning and effortful control (e.g., Garon et al., 2008, Rothbart et al., 1994). Our main aim was to test this hypothesis by studying whether sustained attention at age 1 year can predict individual differences in self-regulatory functions at age 2 years. Longitudinal data from 66 infants and their parents were included in the study. Sustained attention was assessed during free play at age 1 year; executive functioning, measured using an eye-tracking version of the A-not-B task, and effortful control, measured using parental ratings, were assessed at both age 1 and age 2 years. The results did support a longitudinal prediction of individual differences in 2-year-olds’ self-regulatory functions as a function of sustained attention at age 1 year. We also found significant improvement in both executive functioning and effortful control over time, and the two self-regulatory constructs were related in toddlerhood but not in infancy. The study helps increase our understanding of the early development of self-regulatory functions necessary for identifying developmental risks and, in the future, for developing new interventions.

Effect of self-produced locomotion on infant postural compensation to optic flow.

This research demonstrates that experiences associated with early self-produced locomotion facilitate a developmental shift in the visual control of posture. Results showed greater use of optic flow for postural control (as measured in a moving room) after self-produced locomotor experience. Infants with endogenous (creeping) or artificial (walker) self-produced locomotor experience responded to portions of the optic flow field, whereas prelocomotor infants did not. Taken together, these findings suggest that self-produced locomotion facilitates differential use of smaller portions of the optic flow field. Findings will be discussed in terms of how perceptual experiences associated with moving the selfin space bring about important changes in visual proprioception.

Crawling versus Walking Infants' Perception of Affordances for Locomotion over Sloping Surfaces

14-month-old toddlers vs. 8.5-month-old crawling infants were encouraged to ascend and descend a sloping walkway (10 degrees, 20 degrees, 30 degrees, and 40 degrees). Infants in both locomotor groups overestimated their ability to ascend slopes. However, on descending trials where falling was more aversive, most toddlers switched from walking to sliding positions for safe descent, but crawlers plunged down head first and many fell at each increment. Toddlers touched and hesitated most before descending 10 degrees and 20 degrees slopes, and they explored alternative means for descent by testing out different sliding positions before leaving the starting platform. In contrast, crawlers touched and hesitated most before descending 30 degrees and 40 degrees slopes, and they never explored alternative sliding positions. In addition, we analyzed measures of locomotor skill and experience in relation to children's ability to perceive affordances. Findings indicate that children must learn to perceive affordances for locomotion over slopes and that learning may begin by fine-tuning of exploratory activity.

Locomotor Status and the Development of Spatial Search Skills

The principal objective of this experiment was to investigate whether previous reports of a relation between locomotor status and stage 4 object permanence performance generalized to performance on a different object localization task. A secondary objective was to evaluate the contribution of visual tracking as a mediating variable in the relation between locomotor experience and search performance. Precrawling (n = 20), crawling (n = 10), and creeping (n = 18) infants (M = 33 weeks old) were tested using a search task in which either they or the hiding containers were rotated 180 degrees before search was permitted. The results revealed that locomotor status was related to search performance following a displacement of the infant, but not following a displacement of the containers. Moreover, visual tracking of the correct container was not related to locomotor status, even though it was related to search performance. These findings suggest that the effects of locomotor experience on infants' search performance are quite specific and are mediated by a variety of factors that do not necessarily generalize across search tasks.

Early Experience and Emotional Development: The Emergence of Wariness of Heights

Because of its biological adaptive value, wariness of heights is widely believed to be innate or under maturational control. In this report, we present evidence contrary to this hypothesis, and show the importance of locomotor experience for emotional development. Four studies bearing on this conclusion have shown that (1) when age is held constant, locomotor experience accounts for wariness of heights; (2) “artificial” experience locomoting in a walker generates evidence of wariness of heights; (3) an orthopedically handicapped infant tested longitudinally did not show wariness of heights so long as he had no locomotor experience; and (4) regardless of the age when infants begin to crawl, it is the duration of locomotor experience and not age that predicts avoidance of heights. These findings suggest that when infants begin to crawl, experiences generated by locomotion make possible the development of wariness of heights.

Locomotor Experience

2 studies were designed to test the prediction that spatial search strategies (i.e., permanence) may be influenced by locomotor experience. Infants were assigned to 3 groups based on locomotor history: prelocomotor, prelocomotor with walker-assisted experience, and hands-and-knees creeping. Infants in all groups were 8.5 months of age. Results showed that hands-and-knees and walker-assisted locomotor experience facilitated spatial search performance. The longer that infants had been moving, the higher their scores. Furthermore, there were no differences between the hands-and-knees and prelocomotor/walker-assisted groups, suggesting that the relation between locomotor experience and spatial search performance was not merely a function of the maturation of prone progression. A third study found that the quality of locomotion affected object permanence performance: Belly crawlers performed differently than infants with hands-and-knees or walker experience, insofar as they performed at prelocomotor levels regardless of weeks of locomotor experience. Taken together, the pattern of findings suggests that infants with more efficient modes of locomotion are more likely to profit from the experiences generated by locomotion.