Koji Abe

Publications (2)0 Total impact

• Article: A dynamical system analysis of the development of spontaneous lower extremity movements in newborn and young infants.

  Hirotaka Gima, Shohei Ohgi, Satoru Morita, Hiroshi Karasuno, Takayuki Fujiwara, Koji Abe
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  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.
  Journal of PHYSIOLOGICAL ANTHROPOLOGY 01/2011; 30(5):179-86.
• Article: [The developmental characteristics of spontaneous movement in healthy infants].

  Hirotaka Gima, Shohei Ohgi, Hiroshi Karasuno, Takayuki Fujiwara, Koji Abe
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  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.
  No to hattatsu. Brain and development 01/2011; 43(1):19-23.