Abstract
The aim of this study was to evaluate the characteristics of development of spontaneous movements in infants using dynamical systems analysis. The participants were 7 healthy, full-term, newborn infants. A tri-axial accelerometer was used to measure limb acceleration in three-dimensional space. Acceleration signals were recorded on the right wrist, when the infant was in an active alert state, lying in supine. Measurement was carried out every fourth week after birth between the ages of 1 and 5 months old. The recording time was 200 seconds, based on recommendations for this accelerometer. The time-series data was analyzed by non-linear methods using a package (TISEAN) provided with the machine, provided some evidence of non-linear deterministic structure (dimension, maximal Lyapunov exponent). The developmental change in infants' spontaneous movements was shown as “U-shaped”, with the base between 2-3 months, and recovering at 4-5 months (4 of 8 infants in dimension, 6 of 8 infants in maximal Lyapunov exponent). Approximately 4-5 months after birth, infants develop voluntary movement, such as reaching for objects.
