Prelocomotor Infants Research Articles

Locomotion training contributes to 6-month-old infants' mental rotation ability.

This study investigated whether a locomotion training contributes to mental rotation performance in infants. Thirty 6-month-old pre-locomotor infants were randomly assigned to either a locomotion training or a control group which received no training. The general status of motor and cognitive development measured with the Bayley Scales did not differ between the 2 groups. Mental rotation was compared before and after the trainings using a mental rotation task in which infants were habituated to a rotating object and then tested with the same habituation object presented in a previously unseen angle and the corresponding mirror object. Results revealed that only infants in the locomotion training group showed a significant change in their looking durations at the test objects (habituation vs. mirror) in the mental rotation task. This suggests that self-produced locomotion experience can affect infants' mental rotation.

Development of motion speed perception from infancy to early adulthood: a high-density EEG study of simulated forward motion through optic flow

This study investigated evoked and oscillatory brain activity in response to forward visual motion at three different ecologically valid speeds, simulated through an optic flow pattern consisting of a virtual road with moving poles at either side of it. Participants were prelocomotor infants at 4–5 months, crawling infants at 9–11 months, primary school children at 6 years, adolescents at 12 years, and young adults. N2 latencies for motion decreased significantly with age from around 400 ms in prelocomotor infants to 325 ms in crawling infants, and from 300 and 275 ms in 6- and 12-year-olds, respectively, to 250 ms in adults. Infants at 4–5 months displayed the longest latencies and appeared unable to differentiate between motion speeds. In contrast, crawling infants at 9–11 months and 6-year-old children differentiated between low, medium and high speeds, with shortest latency for low speed. Adolescents and adults displayed similar short latencies for the three motion speeds, indicating that they perceived them as equally easy to detect. Time–frequency analyses indicated that with increasing age, participants showed a progression from low- to high-frequency desynchronized oscillatory brain activity in response to visual motion. The developmental differences in motion speed perception are interpreted in terms of a combination of neurobiological development and increased experience with self-produced locomotion. Our findings suggest that motion speed perception is not fully developed until adolescence, which has implications for children’s road traffic safety.

A high-density EEG study of differentiation between two speeds and directions of simulated optic flow in adults and infants.

A high-density EEG study was carried out to investigate cortical activity in response to forward and backward visual motion at two different driving speeds, simulated through optic flow. Participants were prelocomotor infants at the age of 4-5months and infants with at least 3weeks of crawling experience at the age of 8-11months, and adults. Adults displayed shorter N2 latencies in response to forward as opposed to backward visual motion and differentiated significantly between low and high speeds, with shorter latencies for low speeds. Only infants at 8-11months displayed similar latency differences between motion directions, and exclusively in response to low speed. The developmental differences in latency between infant groups are interpreted in terms of a combination of increased experience with self-produced locomotion and neurobiological development. Analyses of temporal spectral evolution (TSE, time-dependent amplitude changes) were also performed to investigate nonphase-locked changes at lower frequencies in underlying neuronal networks. TSE showed event-related desynchronization activity in response to visual motion for infants compared to adults. The poorer responses in infants are probably related to immaturity of the dorsal visual stream specialized in the processing of visual motion and could explain the observed problems in infants with differentiating high speeds of up to 50km/h.

Crawling Experience Relates to Postural and Emotional Reactions to Optic Flow in a Virtual Moving Room

Infants show a dramatic shift in postural and emotional responsiveness to peripheral lamellar optic flow (PLOF) following crawling onset. The present study used a novel virtual moving room to assess postural compensation of the shoulders backward and upward and heart rate acceleration to PLOF specifying a sudden horizontal forward translation and a sudden descent down a steep slope in an infinitely long virtual tunnel. No motion control conditions were also included. Participants were 53 8.5-month-old infants: 25 prelocomotors and 28 hands-and-knees crawlers. The primary findings were that crawling infants showed directionally appropriate postural compensation in the two tunnel motion conditions, whereas prelocomotor infants were minimally responsive in both conditions. Similarly, prelocomotor infants showed nonsignificant changes in heart rate acceleration in the tunnel motion conditions, whereas crawling infants showed significantly higher heart rate acceleration in the descent condition than in the descent control condition, and in the descent condition than in the horizontal translation condition. These findings highlight the important role played by locomotor experience in the development of the visual control of posture and in emotional reactions to a sudden optically specified drop. The virtual moving room is a promising paradigm for exploring the development of perception–action coupling.

Infant visual attention and step responsiveness to optic flow during treadmill stepping

This study examined infant treadmill stepping in two groups of pre-locomotor infants in response to terrestrial optic flow. The optic flow was provided via the treadmill belt for flow translation that was directionally consistent with the forward stepping of the infants. Twelve 2–5-month-old and twelve 7–10-month-old infants participated. Visual attention (duration and direction) and step responsiveness (frequency and step types) were coded from digital video, and visuomotor coupling was examined by temporally juxtaposing the visual attention and step data. Longer durations of visual attention to the patterned belt with increased step frequencies during periods of visual attention were observed, suggesting that the visuotactile calibration afforded by the patterned treadmill belt, increased visuomotor coupling and enhanced the frequency and complexity of stepping in prelocomotor infants. The findings are discussed with regard to sensorimotor experiences that enhance treadmill stepping in infants and that may have application to clinical populations.

Locomotor experience affects self and emotion.

Two studies investigated the role of locomotor experience on visual proprioception in 8-month-old infants. Visual proprioception refers to the sense of self-motion induced in a static person by patterns of optic flow. A moving room apparatus permitted displacement of an entire enclosure (except for the floor) or the side walls and ceiling. In Study 1, creeping infants and prelocomotor/walker infants showed significantly greater postural compensation and emotional responses to side wall movement than did same-age prelocomotor infants. Study 2 used true random assignment of prelocomotor infants to locomotor-training (via a powered-mobility device) and no-training conditions. Experimental infants showed powerful effects of locomotor training. These results imply that locomotor experience is playing a causal role in the ontogeny of visual proprioception.

The relation between infants' perception of catchableness and the control of catching.

The authors studied how infants come to perceive and act adaptively by presenting 35 three- to nine-month-olds with balls that approached at various speeds according to a staircase procedure. They determined whether infants attempted to reach for the ball and whether they were successful (i.e., contacted the ball). In addition, the time and distance of the ball at the onset of the catching movements were measured for the successful interceptions. The authors found that not only catching skill but also the perceptual judgments of the catchableness improved with age; infants started to take their catching ability into account when judging whether a ball was catchable. Moreover, the authors observed that infants who made imprecise perceptual judgments were more likely to use a distance control strategy, whereas infants who made accurate perceptual judgments were more likely to use the more adaptive time strategy to control the catching movements. They conclude that the present study supports the proposal that, even in prelocomotor infants, the development of perception is intricately linked to or constrained by development in the visual control of action.

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.

Crawling experience is related to changes in cortical organization during infancy: evidence from EEG coherence.

Greenough's model of experience-expectant plasticity was used to examine EEG coherence among four groups of 8-month-old infants that varied in hands-and-knees crawling experience. Groups included prelocomotor infants, novice crawlers with 1-4 weeks experience, infants with 5-8 weeks, and long-term crawlers with 9+ weeks experience. Resting EEG was recorded from frontal, parietal, and occipital sites of both hemispheres. EEG coherence between intrahemispheric sites was computed. Novice crawlers (1-4 weeks) displayed greater coherence than either prelocomotor infants or experienced crawlers. These data suggest that the anticipation and onset of locomotion was related to an overproduction of cortico-cortical connections. Pruning of these overabundant connections may be a source of the decrease in coherence as crawling becomes more routine.

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.

Hidden Skills: A Dynamic Systems Analysis of Treadmill Stepping during the First Year

When prelocomotor infants are supported on a motorized treadmill, they perform well-coordinated, alternating stepping movements that are kinematically similar to upright bipedal locomotion. This behavior appeared to be a component of independent walking that could not be recognized without the facilitating context of the treadmill. To understand the ontogenetic origins of treadmill stepping and its relation to later locomotion, we conducted a longitudinal study using an experimental strategy explicitly derived from dynamic systems theory. Dynamic systems theory postulates that new forms in behavior emerge from the cooperative interactions of multiple components within a task context. This approach focuses on the transitions, often nonlinear, where one preferred mode of behavior is replaced by a new form. Specific predictions about these transitions help uncover the processes by which development proceeds. Chapters II, III, and IV introduce dynamic principles of pattern formation and their application to development. In our application of these principles, we tested nine normal infants twice each month beginning from month 1 in a task where the treadmill speed was gradually scaled up and in an additional condition where each leg was driven by the treadmill at a different speed. Kinematic variables were derived from computerized movement analysis equipment and videotaped records. We also collected a number of anthropometric measurements, Bayley motor scores, and a behavioral mood scale for each month. Several infants stepped on the treadmill in their first month, but in all infants performance showed a rapidly rising slope from month 3 to month 6. Infants also showed corresponding improvement in adjustments to speed and relative coordination between the legs. In dynamic terminology, we found evidence that alternating stepping on the treadmill became an increasingly stable attractor during the middle months of the first year. Dynamic predictions that transitions would be characterized by increased variability and sensitivity to perturbation were borne out. Identifying the transitions enabled us to suggest a control parameter or variable moving the system into the stable response to the treadmill. This appeared to be the waning of flexor dominance in the legs during posture and movement that allowed the leg to be stretched back on the treadmill and so elicited the bilaterally alternating response. Further studies are needed to test this hypothesis. This dynamic analysis confirmed earlier suggestions that skill in general, and locomotion in particular, develops from the confluence of many participating elements and showed how emergent forms may result from changes in nonspecific components. A dynamic approach may be useful for understanding ontogenetic processes in other domains as well.

A reexamination of fear and its determinants on the visual cliff.

ABSTRACTRichards and Rader (1983) argue in their recent Psychophysiology paper that crawling experience plays no significant role in the development of visual cliff performance, and also that “fear” is not related to the development of the avoidance of heights. It is our contention that these conclusions rest upon oversimplified assumptions about the nature of fear and its determinants on the visual cliff. A very different set of inferences emerge from an alternative conceptualization of the problem. In contrast to Richards and Rader, we argue that heart rate cannot be simply equated with fear but rather represents one of many loosely correlated indices. Evidence is presented to show that behavioral and cardiac responses converge to demonstrate fear of heights by locomotor infants. It is further argued that the role of crawling experience is not given an adequate test by Richards and Rader. The theoretically important test involves a comparison between locomotor and prelocomotor infants. Data from such comparisons are reviewed and found to support self‐produced locomotion as an important predictor of visual cliff performance.

Cardiac responses on the visual cliff in prelocomotor human infants.

Human infants younger than crawling age yielded reliable cardiac decelerations when placed directly atop the deep side of a visual cliff and generally nonsignificant changes when atop the shallow side. Distress was elicited less frequently on the deep side than on the shallow at these ages, in contrast to the behavior of older infants and other species. Prelocomotor infants thus can discriminate the two sides of the cliff, but not by means of distress at loss of optical support.