Motor asymmetries in the human newborn are state dependent, but independent of position in space.
Human newborns have a preference for turning and maintaining the head to one side of the body. Most studies confirm a right-sided preference in supine. Few have addressed the state dependency of this lateral bias, and even fewer have examined whether it is also expressed in the semi-upright position. We investigated whether it varies as a function of behavioural state and position in space. Kinematic recordings of head movements were made with the newborn secured on a platform in the supine or semi-upright position, which alleviated biomechanical and postural constraints imposed by gravity. Newborns differed as to whether they had a vertex, Caesarean or breech delivery. The majority of infants maintained a right-sided preference in both positions, but it was strongly mediated by state. Delivery type did not account for any lateral bias. These findings provide convincing evidence that a lateral bias in movement and positioning of the head are reflections of active neural processes rooted in the regulation of state.
Rönnqvist
L
L
Department of Psychology, Umeå University, Sweden. louise.ronnqvist@psy.umu.se
Hopkins
B
B
D001696:Biomechanical Phenomena; D036861:Delivery, Obstetric; D006257:Head / Q000502:physiology; D006801:Humans; D018730:Infant Behavior / Q000502:physiology*; D007231:Infant, Newborn; D009068:Movement / Q000502:physiology*; D010827:Physiology / Q000295:instrumentation; D011187:Posture / Q000502:physiology*