Borvendeg, K., & de Groot, L. (2000). The stepping response in early infancy. Neuropediatrics, 31(4), 180–185. https://doi.org/10.1055/s-2000-7459
Postnatally, the stepping response can be elicited right after birth, but soon diminishes and disappears by about 2-3 months of age. It is still not clear if the disappearance of the response is caused by gradual maturation of the central nervous system, environmental factors, or biomechanical factors such as added body weight and/or increased muscle mass of the legs. This clinical study assessed the stepping response in a group of healthy infants (n = 58) at the age of 6 weeks: 37 born preterm and corrected for gestational age. Quantitative measures of stepping response were obtained together with the qualitative measures of behavioural state and the distribution of active and passive muscle power of the legs. Mechanical factors were studied by dividing the infants according to their birth weight status, and calculating the ponderal index (PI), leg volume (LV), and weight gain of each group. Preterm infants show more stepping responses, more muscle power discrepancies, and different leg volumes than their full-term counterparts. In addition, our results reported significant relationship between gestational age and relative birth weight on the manifestation of stepping response. Within the preterm group the responses lingered longer in infants with shorter gestational ages and in those with lower birth weight status. Consequently, this study suggests that environmental experience and the time of birth of the infants play a more significant role than maturation and mechanical factors in the manifestation of the infantile stepping response.
de Klerk, C. C., Southgate, V., & Csibra, G. (2016). Predictive action tracking without motor experience in 8-month-old infants. Brain and cognition, 109, 131–139. https://doi.org/10.1016/j.bandc.2016.09.010
A popular idea in cognitive neuroscience is that to predict others' actions, observers need to map those actions onto their own motor repertoire. If this is true, infants with a relatively limited motor repertoire should be unable to predict actions with which they have no previous motor experience. We investigated this idea by presenting pre-walking infants with videos of upright and inverted stepping actions that were briefly occluded from view, followed by either a correct (time-coherent) or an incorrect (time-incoherent) continuation of the action (Experiment 1). Pre-walking infants looked significantly longer to the still frame after the incorrect compared to the correct continuations of the upright, but not the inverted stepping actions. This demonstrates that motor experience is not necessary for predictive tracking of action kinematics. In a follow-up study (Experiment 2), we investigated sensorimotor cortex activation as a neural indication of predictive action tracking in another group of pre-walking infants. Infants showed significantly more sensorimotor cortex activation during the occlusion of the upright stepping actions that the infants in Experiment 1 could predictively track, than during the occlusion of the inverted stepping actions that the infants in Experiment 1 could not predictively track. Taken together, these findings are inconsistent with the idea that motor experience is necessary for the predictive tracking of action kinematics, and suggest that infants may be able to use their extensive experience with observing others' actions to generate real-time action predictions.
Dominici, N., Ivanenko, Y. P., Cappellini, G., d'Avella, A., Mondì, V., Cicchese, M., Fabiano, A., Silei, T., Di Paolo, A., Giannini, C., Poppele, R. E., & Lacquaniti, F. (2011). Locomotor primitives in newborn babies and their development. Science (New York, N.Y.), 334(6058), 997–999. https://doi.org/10.1126/science.1210617
Størvold, G. V., Aarethun, K., & Bratberg, G. H. (2013). Age for onset of walking and prewalking strategies. Early human development, 89(9), 655–659. https://doi.org/10.1016/j.earlhumdev.2013.04.010
Background: Age for onset of independent walking (AOW) is frequently used as an indicator of the progress of motor development in early life. Yet there is considerable uncertainty in the research literature about the age we should expect children to walk independently, and also whether prewalking strategies are of importance for this milestone. In clinical practice we commonly experience that children start walking at later ages than the standards presented in the Alberta Infant Motor Scale (AIMS), the most frequently used standardized instrument of gross motor development in Norway.
Aims: To investigate the normal distribution of AOW among Norwegian children, which prewalking locomotor strategies (PLS) children used before AOW, and if children who crawled on hands and knees started to walk earlier than children with other strategies.
Design and methods: This cross-sectional study was based on parental self reports from two data sources, i.e. the Norwegian Mother and Child Cohort Study (MoBa, n = 47,515), and project specific regionally collected data (n = 636).
Results: Half of the Norwegian children had started to walk at 13 months (median). Twenty-five percent walked at 12 months and 75% of the children walked at 14 months. Mean AOW, claiming at least 5 independent steps, was 13.1 (1.91)months. Children who used crawling on hands and knees (84.5%) as PLS started to walk unaided 0.9 months earlier (95% CI = 0.32-1.49, p < 0.05) than bottom shufflers (7.1%).
Conclusion: Norwegian children start to walk considerably later than standards reported in AIMS. Crawling on hands and knees is associated with an earlier onset of walking.