Compensatory eye movements during head and body rotation in infants

Head and eyes: Looking behavior in 12- to 24-month-old infants

This study demonstrates evidence for a foundational process underlying active vision in older infants during object play. Using head-mounted eye-tracking and motion capture, looks to an object are shown to be tightly linked to and synchronous with a stilled head, regardless of the duration of gaze, for infants 12 to 24 months of age. Despite being a developmental period of rapid and marked changes in motor abilities, the dynamic coordination of head stabilization and sustained gaze to a visual target is developmentally invariant during the examined age range. The findings indicate that looking with an aligned head and eyes is a fundamental property of human vision and highlights the importance of studying looking behavior in freely moving perceivers in everyday contexts, opening new questions about the role of body movement in both typical and atypical development of visual attention.

Cervico-ocular Reflex Is Increased in People With Nonspecific Neck Pain

BACKGROUND

Neck pain is a widespread complaint. People experiencing neck pain often present an altered timing in contraction of cervical muscles. This altered afferent information elicits the cervico-ocular reflex (COR), which stabilizes the eye in response to trunk-to-head movements. The vestibulo-ocular reflex (VOR) elicited by the vestibulum is thought to be unaffected by afferent information from the cervical spine.

OBJECTIVE

The aim of the study was to measure the COR and VOR in people with nonspecific neck pain.

DESIGN

This study utilized a cross-sectional design in accordance with the STROBE statement.

METHODS

An infrared eye-tracking device was used to record the COR and the VOR while the participant was sitting on a rotating chair in darkness. Eye velocity was calculated by taking the derivative of the horizontal eye position. Parametric statistics were performed.

RESULTS

The mean COR gain in the control group (n=30) was 0.26 (SD=0.15) compared with 0.38 (SD=0.16) in the nonspecific neck pain group (n=37). Analyses of covariance were performed to analyze differences in COR and VOR gains, with age and sex as covariates. Analyses of covariance showed a significantly increased COR in participants with neck pain. The VOR between the control group, with a mean VOR of 0.67 (SD=0.17), and the nonspecific neck pain group, with a mean VOR of 0.66 (SD=0.22), was not significantly different.

LIMITATIONS

Measuring eye movements while the participant is sitting on a rotating chair in complete darkness is technically complicated.

CONCLUSIONS

This study suggests that people with nonspecific neck pain have an increased COR. The COR is an objective, nonvoluntary eye reflex and an unaltered VOR. This study shows that an increased COR is not restricted to patients with traumatic neck pain.

Proprioceptive influence on the optokinetic nystagmus

The influence of neck and leg proprioceptive inputs on optokinetic-induced quick phases was studied in humans. Ten subjects received unidirectional horizontal optokinetic stimulation (10-20%/s) during sinusoidal neck, leg and combined neck + leg proprioceptive stimulation. The optokinetic reflex was measured by electro-oculography. Neck stimulation induced a shift in the nystagmus beating field in the opposite direction to body movement (gain 0.3 0.4, phase 140-180 degrees). The beating field shift resulted totally from the amplitude and frequency modulation of optokinetic quick phases, as slow phases were not affected. Leg proprioceptive stimulation induced a similar effect, but the phase of the response lagged by approximately 90 degrees compared with that of neck response. With combined neck + leg stimulation, the amplitude of the effect was a sum of the separate effects, but the phase coincided with that of the leg response. This suggests that neck and leg proprioceptive signals do not add linearly and that the leg signal determines the time of the response.

Peripheral stimulus localization by infants with eye and head movements during visual attention

The effect of attention to a focal stimulus on 14, 20 and 26-week-old infant's peripheral stimulus localization with eye and head movements was examined in this study. Fixation was engaged on a stimulus in the central visual field and a stimulus was presented in the periphery immediately or after a delay. Peripheral stimulus localization occurred less frequently near the beginning of fixation and when a significant heart rate deceleration had occurred (sustained attention), compared with when no focal stimulus was present or after heart rate had returned to prestimulus level (attention termination). Localization was accompanied by head movements on more than two-thirds of the trials, and the likelihood of head movements was positively associated with stimulus eccentricity. The saccades to localize the peripheral stimulus had unusually high velocities in the attention conditions for the two older aged groups relative to their saccades in inattentive conditions. There were unusual "localizing head movements" in the attention conditions in the absence of localizing saccades or changes in fixation for the two older age groups. Infant attention modulates eye movement characteristics of infants. These data also support the hypothesis that eye and head movement systems are relatively independent in the infant, and that eye-head relations during infant attention may be different from during inattention.

Development of high frequency vestibulo-ocular responses to active head shaking

Computer aided active head shaking test has several advantages because it can be used clinical at frequencies higher than 2 Hz. In this study, VOR gain and phase were examined over age. For this experiment, we designed an original measurement system composed of EOG, an angular velocity sensor and a microcomputer. VOR gain was expressed by transfer function. Forty normal subjects ranging from 10 to 75 were examined for high frequency VOR responses to active head shaking. VOR gain at frequencies higher than 2 Hz attained the same value as that seen in children below the age of 10 years. The VOR gain was nearly 1 within 2 Hz, decreasing with frequencies above 4 Hz. The effect of aging was shown at frequencies of more than 4 Hz, and appeared in patients above 50 years of age. No obvious phase lag was observed within 5 Hz.

Infant eye movements: quantification of the vestibulo-ocular reflex and visual-vestibular interactions

The gain of the infant vestibulo-ocular reflex (VOR) was determined when infants were rotated either in total darkness or while they viewed visual targets consisting of a stationary spot or a full field of black and white stripes. The average VOR gain in the dark was 1.03 +/- 0.014 for 1-4-month-old infants and 0.59 +/- 0.03 for adult subjects tested with appropriate controls for psychological "set". Longitudinal studies showed no significant change in gain over the first 4 months of life. Although the presence of the spot or full-field striped background increased adult compensatory gains from 0.59 to 1.0, the same visual targets had no effect on infant gains. Thus, an infant's VOR gain of nearly 1.0 apparently reduces reliance on the poorly developed smooth pursuit and optokinetic systems that, in adults, help the VOR provide perfect ocular stabilization.