Quantitative assessment of the development of reaching in healthy full term and preterm infants at 7, 9, and 12 months
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Abstract
The purpose of this study was to developmentally analyze the visual-motor control of reaching movements in healthy full term and preterm infants at 7, 9, and 12 months of age.
There were a series of two parallel longitudinal studies of infants tested at the above ages. Study 1 had 8 term infant subjects and Study 2 had 11 preterm infant subjects. Preterm infants were tested at adjusted ages for prematurity (AA) as well as at 12 months chronological age (CA). Infants repeatedly reached for a stationary object. Positional data were recorded using WATsmart (camera/computer) technology and analyzed for straightness and duration of reach, number of movement units (MUs) and duration of the first MU. Visual fixation was behaviorally evaluated from a video recording of the session. Results were analyzed using statistical significance and the effect size, the degree to which means change in the hypothesized direction.
In Study 1 reach of term infants between 7 and 12 months became straighter, smoother, had a greater relative duration of the first MU, but did not become faster. In Study 2 reach of preterm infants between 7 and 12 months AA became straighter, smoother, but did not attain a greater relative duration of the first MU nor become faster. At 12 months CA, preterm infants were more immature than at 12 months AA in duration of reach and relative duration of the first MU. In both studies, infants constantly visually fixated on the reaching task at all ages.
Trajectory aspects of reach in both studies changed in the direction of adult-like reach although neither infant group attained a mature level of reach. Changes in reach were not due to differences in looking at the task but may have occurred because of developmental changes in fine and gross motor, cognitive, and perceptual performance. Although changes in healthy preterm infant reaching movements paralleled those of term infant reaching, heal thy preterm infants even at 12 months may still have subtle differences in information processing and visual-motor strategies which may influence the control of reaching movements.
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Dissertation (Sc.D.)--Boston University
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