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Maryse Lassonde, Emmanuel Tremblay, Franco Lepore, Marie-Sylvie Roy, Nicole Fallaha, Michelle McKerral; Delayed early primary visual pathway development in premature infants: high density electrophysiological evidence . Journal of Vision 2010;10(7):461. doi: 10.1167/10.7.461.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of the present study was to investigate the effects of premature birth on visual system development in the first six months of life. Early and late visual evoked potential (VEP) components and their topographical distribution related to preferential or combined activation of the magnocellular (M) and parvocellular (P) visual systems were obtained in 21 preterm and 32 fullterm infants. Participants were infants of extremely low birth weight (ELBW), weighing between 688-1360g (mean gestational age: 26.3 wks) and low birth weight (LBW), with a weight between 983-1603g (corrected mean gestational age: 29.8 wks). The fullterm group birth weights ranged from 2700-4439g (mean gestational age: 39.2 wks). Three stimulus conditions, a low spatial frequency (0.5 cpd) presented at either of two Michelson contrast levels (10% and 95%), and a high spatial frequency (2.5 cpd) at 95% contrast, were used in order to preferentially activate the M system, the P system, or both. Results indicate impaired function overall in preterm infants compared to fullterm babies. Furthermore, the severity of this impairment was directly related to the degree of prematurity. The cortical topography showed, by its diffuse nature, that both M and P systems (P1 and N1 components, respectively) remained immature until 6 months of corrected age, after which it normalized. However, at 3 months of age, under the optimal condition (Low95%) that stimulated both pathways simultaneously, the N2 component (generally associated with motion perception) obtained in premature infants was of larger amplitude than in fullterm ones, likely reflecting predominant activation of the M system in this group by the apparent motion inherent in the stimulation procedure. Furthermore, a reduced motion adaptation (expressed in the P2 component) at 6 months of age, in combination with the immature topography, indicate a slowed development of associative visual cortical areas in premature infants.
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