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Compensatory eye movements during head and body rotation in infants
1Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis 55455.
Insights
Infant eye movements show a developing vestibulo-ocular reflex (VOR) and a strong cervico-ocular reflex (COR). These reflexes, crucial for balance and vision, adapt with age and visual input.
Area of Science:
- Vestibular Neuroscience
- Developmental Neuroscience
- Ophthalmology
Background:
- The vestibulo-ocular reflex (VOR) stabilizes gaze during head movements.
- The cervico-ocular reflex (COR) also contributes to gaze stabilization, particularly in response to neck rotation.
- Understanding these reflexes in infants is crucial for assessing visual and vestibular development.
Purpose of the Study:
- To measure infant eye movements during rotation to assess the VOR and COR.
- To investigate the age- and frequency-dependency of these reflexes in early development.
- To examine the effect of visual fixation on VOR and COR gain in infants.
Main Methods:
- Infant eye movements were recorded in 2- and 4-month-olds during sinusoidal rotation (0.1-0.5 Hz) in light and dark.
- A specialized infant seat was used to control rotational stimuli.
- VOR and COR responses were analyzed for phase and gain.
Main Results:
- Infant VOR phase was compensatory, with gains between 0.4-1.4, similar to adults.
- COR gains in infants were 4-6 times larger than in adults and showed frequency- and age-dependency.
- Visual fixation increased VOR and combined VOR+COR gains significantly in infants.
Conclusions:
- Infant COR is prominent and developmentally dynamic, suggesting ongoing maturation of the infant nervous system.
- The interaction of VOR and COR contributes to gaze stability in infants.
- Visual input significantly modulates infant gaze stabilization reflexes, potentially exceeding adult capabilities under specific conditions.
Abstract:
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.