Factors Influencing the Asymetrical Tonic Neck Reflex in Normal Infants

The purpose of this study was to evaluate the effect of the following factors on achievement of head position and incidence, strength, and duration of the asymmetrical tonic neck reflex: 1) method of eliciting the reflex, 2) extent of head turning, and 3) direction of head turning. Subjects included 20 - 4 to 10 week old infants. Supine infants were videotaped during eight trials representing all combinations of the three factors. Head turning was elicited actively by having the infant follow a rattle or, passively, by having the examiner turn the infant's head; the head was turned to approximately 70 degrees (full turn) or 30 degrees (partial turn) from vertical; and the head was turned to the left or right. Passively turning the head fully to the side was most effective in achieving the intended head position. Full head turns were most effective in eliciting the reflex, and the reflex was stronger and lasted longer during full head turns. No difference in the three measures of the reflex occurred as a r...