The aim of this semilongitudinal study was to investigate the development of central visual pathways in children born preterm but without major neurologic impairments and to establish their cognitive and behavioral profile at school age. Ten children born preterm were assessed at 6 months and at school age, using visual evoked potentials at both time points and cognitive and behavioral tests at school age. We also tested 10 age-matched children born full-term. At 6 months' corrected age, we found no significant differences between preterm and full-term groups for either amplitude or latency of N1 and P1 components. At school age, the preterm group manifested significantly higher N1 amplitudes and tended to show higher P1 amplitudes than the full-term group. We found no significant differences in cognitive and behavioral measures at school age. These results suggest that preterm birth affects visual pathways development, yet the children born preterm did not manifest cognitive problems.

ResumenLos nacimientos prematuros (≤ 37 semanas de gestación) se consideran una de las causas más importantes de mortalidad perinatal en las sociedades industrializadas. Hoy en día, gracias a la mejora de los cuidados pre-peri-y post-natales, es posible salvar a niños con edades y pesos gestacionales significativamente menores que anteriormente. Con el aumento de la tasa de supervivencia, cada vez más estudios se interesan por el impacto de la prematuridad en el neurodesarrollo de niños nacidos a las 37 semanas de gestación o incluso antes. En efecto, los estudios realizados hasta este momento indican que los niños prematuros tienen alto riesgo de presentar problemas de orden cognitivo, comportamental y de aprendizaje. Los mismos pueden mantenerse hasta la edad escolar e incluso hasta la adolescencia y la edad adulta. Esta revisión de la literatura tiene por objeto presentar los distintos problemas cognitivos, comportamentales y de aprendizaje documentados en estudios recientes interesados por las consecuencias de la prematuridad. Palabras clave: Prematuridad; cognición; comportamiento; problemas de aprendizaje. ResumoNascimentos pré-termo (≤ 37 gestational weeks) tem sido identificados como uma das causas mais importantes de mortalidade perinatal em sociedades industrializadas. Com a melhoria dos serviços pré-peri-e pós-natais, atualmente é possível salvar estas crianças com significativos baixos peso e idade gestacional. Frente às crescentes taxas de sobrevivência, cada vez mais estudos abordam o impacto da prematuridade no neurodesenvolvimento de crianças nascidas até 37 semanas de gestação. Pesquisas até então sugerem que crianças prematuras apresentam alto risco de dificuldades cognitivas, comportamentais e de aprendizagem, sendo que estas últimas podem se prolongar até a idade escolar, mantendo-se até mesmo na adolescência e/ou vida adulta. Esta revisão visou a identificar tais dificuldades em investigações recentes sobre as consequências da prematuridade. Palavras-chave: Prematuridade; cognição; comportamento; dificuldades de aprendizagem. AbstractPreterm births (≤ 37 gestational weeks) have been identified as one of the most important cause of perinatal mortality in industrialized societies. With improvement in pre-peri-and post-natal care, it is now possible to save these children at significantly lower weight and gestational age than previously. With increasing survival rates, more and more studies address the impact of prematurity on the neurodevelopmental outcomes of children born at or before 37 weeks of gestation. Studies to date indicate that children born prematurely are at high risk of experiencing cognitive, behavioural and learning problems, and that the latter can last up to school age and even into adolescence and/or adulthood. The aim of this review is to identify the various cognitive, behavioural and learning difficulties documented in recent studies investigating the consequences of prematurity.

Over the last two decades, the hypothesis of a magnocellular deficit in dyslexia has raised considerable interest and controversy. Using an electrophysiological procedure (visual evoked potentials, VEP), we compared magnocellular and parvocellular contrast and spatial frequency-response functions between phonological dyslexics (n = 16) and a typical reading group (n = 12) matched for age and socioeconomic background. No significant differences were found between the two groups in the amplitude of the VEP components associated with either magnocellular or parvocellular responses. However, topographic analyses revealed a group difference in the distribution of amplitude in the right frontal and left temporal regions, which appeared to be underactivated in dyslexics. These results suggest a deficit in the higher-level cortical regions involved in phonological and/or linguistic processing, and calls into question the notion of a magnocellular involvement in dyslexia.

To date, very little is known about the normal development trajectory of visual texture segregation, or how it is affected by preterm birth. The goal of this study was to characterize the development of visual texture segregation using texture segregation visual evoked potentials (tsVEPs) in children born full-term and children born preterm without major neurological impairment. Forty-five full-term and 43 preterm children were tested at either 12, 24 or 36 months of age (corrected age for prematurity at 12 and 24 months old). VEPs were obtained using two lower-level stimuli defined by orientation (oriVEP) and two higher-level stimuli defined by texture (texVEP). TsVEP was obtained by dividing by two the subtraction of oriVEP from texVEP. Results show a clear maturation of the processes underlying visual texture segregation in the full-term group, with a significant N2 latency reduction between 12 and 36 months of age for all conditions. Significant N2 amplitude reduction was observed for oriVEP between 12 and 24 months, as well as for texVEP between 12 and 24 months, and 12 and 36 months. Comparison between full-term and preterm children indicated significantly lower N2 amplitude for the preterm group at 12 months for oriVEP and texVEP. These differences were no longer apparent at 24 months of age, suggesting that children born preterm catch up with their full-term counterparts somewhere between 12 and 24 months of age. Our results appear to reflect a maturational delay in preterm children in both lower-level and higher-level visual processing during, at least, early childhood.

No abstract

No abstract