title: A dynamical system analysis of the development of spontaneous lower extremity movements in newborn and young infants.
abstract: This study's aim was to evaluate the characteristics of newborn and young infants' spontaneous lower extremity movements by using dynamical systems analysis. Participants were 8 healthy full-term newborn infants (3 boys, 5 girls, mean birth weight and gestational age were 3070.6 g and 39 weeks). A tri-axial accelerometer measured limb movement acceleration in 3-dimensional space. Movement acceleration signals were recorded during 200 s from just below the ankle when the infant was in an active alert state and lying supine (sampling rate 200 Hz). Data were analyzed linearly and nonlinearly. As a result, the optimal embedding dimension showed more than 5 at all times. Time dependent changes started at 6 or 7, and over the next four months decreased to 5 and from 6 months old, increased. The maximal Lyapnov exponent was positive for all segments. The mutual information is at its greatest range at 0 months. Between 3 and 4 months the range in results is narrowest and lowest in value. The mean coefficient of correlation for the x-axis component was negative and y-axis component changed to a positive value between 1 month old and 4 months old. Nonlinear time series analysis suggested that newborn and young infants' spontaneous lower extremity movements are characterized by a nonlinear chaotic dynamics with 5 to 7 embedding dimensions. Developmental changes of an optimal embedding dimension showed a U-shaped phenomenon. In addition, the maximal Lyapnov exponents were positive for all segments (0.79-2.99). Infants' spontaneous movement involves chaotic dynamic systems that are capable of generating voluntary skill movements.
authors.affiliation: School of Physical Therapy, Koriyama Institute of Health Sciences, Fukushima, Japan. h-gima@k-tohto.ac.jp
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Gima
authors.forename: Shohei
authors.initials: S
authors.lastname: Ohgi
authors.forename: Satoru
authors.initials: S
authors.lastname: Morita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Karasuno
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Koji
authors.initials: K
authors.lastname: Abe
mesh_terms: D000054:Acceleration; D000465:Algorithms; D002657:Child Development / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*