A comparison of the developmental characteristics of spontaneous upper extremity movements between healthy full-term infants and premature infants with brain injuries

　This study’s aim was to evaluate the characteristics of spontaneous upper extremity movements of premature infants with brain injuries by using dynamical systems analysis. Participants were 4 infants with brain injuries (3 boys and 1 girl, median birth weight and gestational age were 1367.5 g and 30.0 weeks) and 7 healthy full-term newborn infants (3 boys and 4 girls, median birth weight and gestational age were 2990.7 g and 39.0 weeks). We measured limb movement acceleration in 3-dimentional space using a tri-axial accelerometer. Movement acceleration signals were recorded during 200 s from the right wrist when the infant was in an active alert state and lying supine (sampling rate 200 Hz). Data were analyzed nonlinearly. The optimal embedding dimension (OED) values for infants with brain injuries at 3 months were significantly higher than healthy full-term infants, and the OED and MLE values in infants with brain injuries displayed uncorrelated change profiles. Uncorrelated change profiles of the OED and MLE values revealed that incoordination of the number of motor system component and complexity of appeared spontaneous movements. It suggests that infants with brain injuries have difficulties with self-organization processes. Our results suggest that this method makes it possible to detect early developmental disorders such as cerebral palsy.