Compensatory eye movements during head and body rotation in infants

Eye movements were measured in 2- and 4-month-old infants during rotation in the light and in the dark using a specially constructed infant seat that was rotated sinusoidally at 0.1, 0.25 and 0.5 Hz. As in adults, the phase of the vestibulo-ocular reflex (VOR) was nearly compensatory with respect to head position, and the gain values were generally in the range between 0.4 and 1.4. There were two types of phases for the cervico-ocular (COR) responses: compensatory and anticompensatory. The gain of the COR was 4-6 times larger than that reported for adults. In addition, it was both frequency- and age-dependent. These characteristics of the COR may reflect developmental processes in the infant nervous system. The interaction of the two reflexes (VOR + COR) gave responses similar to when the VOR was elicited alone. The subjects use of a fixation light raised the gain of the VOR and VOR + COR to about 1.67 and 1.44, respectively. These values were higher than most gains reported for adults. However, they were close to what was predicted (1.53) for the experimental conditions wherein fixation was on a target 25 cm in front of the eyes.