Eye-Mouth Associated Movement in the Human Newborn and Very Young Infant

Abstract

BackgroundThe aim of this study is to demonstrate that goal-directed eye-mouth associated movement exists in the newborn and very young infant. MethodsThe participants were 17 healthy term newborns or very young infants whose ages at the time of the first examination ranged from 1 to 24 days. The examiner held the tip of an index finger 20 to 30 cm in front of a participant's mouth, then suddenly moved it directly toward the mouth. Thirteen of the participants were also examined with the examiner's palm as the visual stimulus. The response was judged to be positive if clear mouth opening was elicited as the fingertip or palm was approaching the mouth. ResultsIn the examinations using a fingertip, the frequency of a positive response as to the total number of examinations in the different age groups within the first two months of life ranged between 43.9% and 48.8%, and precipitously decreased to 6.3% at two months of age. A positive response was not elicited from age three months. On the other hand, in the examinations using a palm, the frequency of a positive response was 5.0% in the newborns, and 6.7% in the infants aged between seven days and one month. A positive response was never obtained from two months of age. ConclusionThis study demonstrated that visually guided mouth opening toward an approaching target exists in the human newborn. The eye-mouth associated movement may be controlled through rudimentary but functional visuomotor circuits in the brain interconnecting different cortices.