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Karen Dobkins, Rain Bosworth, Joseph McCleery; Teasing apart contributions of visual experience and biological maturation on the development of contrast sensitivity. Journal of Vision 2007;7(9):545. doi: 10.1167/7.9.545.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the extent to which early visual development is governed by visual experience vs. biological maturation, we asked whether contrast sensitivity (CS) for luminance and chromatic stimuli is better predicted by postnatal age (PNA) or biological age (BA, time since conception), the latter calculated as the sum of PN and gestational period (GP).
Methods: Using FPL, we measured CS in full-term 2-month-olds (n=44) and 6-month-olds (n=130) to chromatic (isoluminant, red/green) and luminance gratings (0.27 cpd, 4.2 Hz). GP was calculated by comparing subjects' irthdates with due dates, accounting for the known error in ultrasound dating (Sladkevicius et al 2005). To tease apart factors contributing to CS, we employed a multiple regression analysis to determine percent variance (r-squared) in CS accounted for by PNA and GP jointly vs. each factor alone.
Results: GP was not a significant predictor of either chromatic or luminance CS (0%; p=NS) in 6 month olds, while in 2-month-olds, it predicted 5% of the variance in both chromatic and luminance CS (p∼0.09). PNA predicted a similar amount of variance, 7% and 9% (both p<'0.002) for chromatic and luminance CS, respectively, in 6 month olds, while in 2-month-olds, it predicted 18% of the variance in chromatic CS (p=0.003), but only 1% in luminance CS (p=NS). Jointly, GP and PNA (which reflect BA), in 2-month-olds, predicted 24% of the variance in chromatic CS, which was greater than either GP or PNA alone. This was not the case in 6-month-olds, since GP did not account for any variance.
Conclusions: Early in development, chromatic CS is influenced by visual experience, while luminance CS is dominated by biological maturation. At older ages, only visual experience influences, and roughly equally so, chromatic and luminance CS. This suggests that, with age, effects of biological maturation decrease and effects of visual experience increase.
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