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R. G. Bosworth, B. Hinga, S. L. Robbins, K. R. Dobkins; Longitudinal study of chromatic and luminance contrast sensitivity in full-term and pre-term infants. Journal of Vision 2006;6(6):287. doi: 10.1167/6.6.287.
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Purpose: Previous VEP studies have investigated the development of chromatic (Chr) and luminance (Lum) contrast sensitivity. Here, we used a psychophysical technique to longitudinally track the development of Chr and Lum sensitivity between 2–7 months. In addition, we tested pre-term infants to determine whether Chr and Lum sensitivity are differentially affected by extra-uterine visual exposure.
Methods: Using forced-choice preferential looking (FPL), contrast thresholds were obtained for chromatic (Chr, red/green isoluminant) and luminance (Lum, black/yellow) sinusoidal gratings (15 by 15 deg; 0.27 cpd; 4 Hz; mean luminance = 12 cd/m2). The Chr stimuli were set to isoluminance using the mean isoluminant point from 24 adults using a minimal motion technique. Cone contrasts of the stimuli were: Lum = 2–46%, Chr = 2–24%. Weibull functions were fit to the data to obtain a threshold, and then sensitivity, for each infant. Log Lum:Chr sensitivity ratios were calculated for each infant.
Results: Data from 25 full-term infants show that, consistent with previous results, Lum sensitivity is greater than Chr sensitivity at 2 and 3 months of age. By around 4 or 5 months, there is a reversal in the Lum:Chr ratio, such that Chr sensitivity is greater. Preterm infants show a similar change in Lum:Chr ratio with age, however, more subjects will be needed to determine whether their Lum:Chr ratios are dictated by adjusted age or postnatal age.
Conclusions: Infants become relatively more sensitive to chromatic stimuli with increasing age, which suggests differential rates of magnocellular vs. parvocellular pathway development.
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