The development of mature patterns of head-eye coordination in the human infant.

Four experiments examined the initiation of coordinated head and eye movement and the vestibulo-ocular reflex (VOR). Experiment 1 examined the initiation of head and eye movement to stationary, peripheral, visual targets. In adults we would expect to see an eye movement followed by a head movement. The VOR would maintain field-holding while the head rotated. Three-month-olds produced the same pattern of coordinated movement as seen in adults, 2-mth-olds produced only eye movements, i.e., no apparent head movement. Experiment 2 examined the gain of the VOR in darkness in 2- and 3-mth-olds and an adult. The VOR at all ages was qualitatively and quantitatively the same. Experiment 3 examined the gain of the VOR during visual fixation. The gain in 3-mth-olds shoed a significant increase as compared to gain in darkness. The same increment was seen in the adult. Two-month-olds showed no facilitation of gain. Experiment 4 examined tonic suppression of the VOR during visual fixation. While total suppression was seen in adult and the 3-mth-olds, no suppression was apparent in 2-mth-olds. Overall, the data indicate the communication between the visual, vestibular, head movement, and eye movement systems shows a marked shift between the second and third month of life.