Mild traumatic brain injury induces prolonged visual processing deficits in children.

PRIMARY OBJECTIVE: To compare the sensitivity to simple and complex visual stimuli of children who have sustained a mild traumatic brain injury (mTBI) to that of matched non-injured children and to determine the evolution of visuo-perceptual performance over time. RESEARCH DESIGN: A prospective design was used to assess 18 children with mTBI and 18 matched healthy controls (8-16 years of age). METHODS AND PROCEDURES: Sensitivity to static and dynamic forms of simple (first-order) and complex (second-order) stimuli were assessed at 1, 4 and 12 weeks post-injury and at equivalent times for controls. Orientation and direction identification thresholds were measured for all participants for static and dynamic conditions, respectively. In addition, sensitivity to radial optic flow (inward vs outward), a complex motion stimulus, was assessed. MAIN OUTCOMES AND RESULTS: Thresholds measured from all complex stimuli were significantly affected for the mTBI children over time whereas no difference in threshold between groups across all testing conditions was found for simple, first-order information. Sensitivity to all complex stimuli was still affected 12 weeks after the injury. CONCLUSION: These findings suggest that injured children present selective processing deficits for higher-order information and that this deficit persists over relatively long periods. Such measures could be useful to assess children who have sustained mTBI and possibly contribute to identifying potential risks of returning these children to demanding physical activities.

Infant sensitivity to radial optic flow fields during the first months of life.

Little is known about the development of the sensitivity for "optic flow," a large-scale pattern perceived during locomotion. The present study aimed to examine infants' coherence thresholds to radial optic flow motion during the first months of life. Using a forced-choice preferential looking technique, infants' sensitivities were measured with a moving radial stimulus varying in coherence on one side and a corresponding non-directional radial noise pattern on the other. Coherence thresholds for 11 infants from each of 2, 4, 6, 8, and 10 months of age groups were studied by a constant stimuli method. In the second experiment, seven infants were followed longitudinally (tested at 2, 4, 6, and 8 months) using the same stimuli. Results of both studies demonstrated significant improvement for the sensitivity of expanding radial motion during the first months of life. Finally, the 2 directions of radial motion were tested (expanding and contracting) for participants followed longitudinally (from 2 to 8 months). Data showed superior sensitivity for expansion versus contraction direction of motion. This dissociation may suggest that sensitivity to direction corresponding with forward locomotion (expansion) develops at a faster rate than the opposite direction encountered when moving backwards (contraction). The sensitivity improvement for expanding patterns likely reflects the maturation of cerebral areas subtending motion integration in infancy.

Maturation of the sensitivity for luminance and contrast modulated patterns during development of normal and pathological human children.

Any object may contain at least two spatio-temporal components referred to as first- and second-order, respectively, defined by spatial-temporal luminance modulation or by contrast, texture or depth modulation. This study investigates form sensitivity of infants, normals, premature or strabismic. A two-alternative forced-choice preferential looking procedure was used in monocular and binocular condition. Maturation profile for both stimuli was similar in the control group. Strabismic infants showed a vertical offset in maturation, which affected the second-order more severely. The pre-term group showed a lag of second-order sensitivity. Our results underline differences between first- and second-order processing.