Biomedical subjects

Marie-Sylvie Roy

Publications and source records attributed to Marie-Sylvie Roy.

4 recordsLinked to original sources

PubMed2007

Developmental delay and magnocellular visual pathway function in very-low-birthweight preterm infants.

This study investigated the effect of very preterm birth (gestation < or =30wks) and very low birth weight (< or =1500g) on the development of magnocellular and parvocellular visual processing streams. Participants were preterm infants (n=55: 31 females, 24 males) born between 24 and 30 weeks'gestation (mean 27.4wks [SD 1.3]), weighing between 720 and 1470g (mean 1015g [SD 215]) and term infants (n=52: 27 females, 25 males) born between 38 and 42 weeks'gestation (mean 39.4wks [SD 0.9]), weighing between 2670 and 4405g (mean 3549g [SD 440]). Visual-evoked potentials to phase-reversing sine-wave gratings, varying in spatial frequency and contrast, were used to elicit magnocellular and parvocellular specific responses. Previous studies found that the N1 component reflects the parvocellular response, while P1 reflects the magnocellular response in adults and infants. Findings from the current study indicate significantly lower P1 amplitudes in preterm compared with term infants under most conditions. No difference was found for the amplitude of the N1 waveform. Results indicate that, for the age-range tested, preterm birth has little effect on the development of parvocellular function, while it appears to disrupt the development of magnocelluar function.

Contrast Sensitivity↗

PubMed2006

Alterations of visual evoked potentials in preschool Inuit children exposed to methylmercury and polychlorinated biphenyls from a marine diet.

The aim of the present study was to assess the impact of chronic exposure to polychlorinated biphenyls (PCBs) and methylmercury on visual brain processing in Inuit children from Nunavik (Northern Québec, Canada). Concentrations of total mercury in blood and PCB 153 in plasma had been measured at birth and they were again measured at the time of testing in 102 preschool aged children. Relationships between contaminants and pattern-reversal visual evoked potentials (VEPs) were assessed by multivariate regression analyses, taking into account several potential confounding variables. The possible protective effects of selenium and omega-3 polyunsaturated fatty acids against methylmercury and PCB toxicity were also investigated. Results indicate that exposure to methylmercury and PCBs resulting from fish and sea mammal consumption were associated with alterations of VEP responses, especially for the latency of the N75 and of the P100 components. In contrast, the concomitant intake of omega-3 polyunsaturated fatty acids was associated with a shorter latency of the P100. However, no significant interactions between nutrients and contaminants were found, contradicting the notion that these nutrients could afford protection against environmental neurotoxicants. Interestingly, significant associations were found with concentrations of neurotoxicants in blood samples collected at the time of testing, i.e. at the preschool age. Our findings suggest that VEP can be used as a valuable tool to assess the developmental neurotoxicity of environmental contaminants in fish-eating populations.

Animals↗

PubMed2004

Influence of the state of alertness on the pattern visual evoked potentials (PVEP) in very young infant.

The aim of the study was to evaluate the pattern visual evoked potentials (PVEP) combined with an optimal state of vigilance, called liberated state (LS), in order to improve testing in very young infants. Transient PVEP were recorded in response to a checkerboard pattern of 120, 60 and 30 min of arc. in 56 fullterm newborns and 79 preterm infants from birth to 4 months of age. In the fullterms, 28 infants in each group were tested in LS or spontaneous alertness (SA) while in the preterms, 48 infants in each group were tested in LS or SA. No significant difference was found in the amplitude and/or peak time of the PVEP responses between subjects tested in LS compared to SA groups. However, the LS condition improved by approximately 25% the feasibility of prolonged PVEP testing in preterms aged less than 2 months (corrected age). This suggest that the LS condition enhances the clinical feasibility of PVEP testing in very young infants and should be used to optimize the evaluation of visual development in high risk infants in this age group.

Adult↗

PubMed2003

Magnocellular and parvocellular developmental course in infants during the first year of life.

The visual system undergoes major modifications during the first year of life. We wanted to examine whether the magnocellular (M) and parvocellular (P) pathways mature at the same rate or if they follow a different developmental course. A previous study carried out in our laboratory had shown that the N1 and P1 components of pattern visual evoked potentials (PVEPs) were preferentially related to the activity of P and M pathways, respectively. In the present study, PVEPs were recorded at Oz in 33 infants aged between 0 and 52 weeks, in response to two spatial frequencies (0.5 and 2.5 c deg(-1)) presented at four contrast levels (4, 12, 28 and 95%). Results indicate that the P1 component appeared before the N1 component in the periods tested and was unambiguously present at birth. The P1 component showed a rapid gain in amplitude in the following months, to reach a ceiling around 4-6 months. Conversely, the N1 component always appeared later and then gained in amplitude until the end of the first year without reaching a plateau. Latencies were also computed but no developmental dissociation was revealed. Results obtained on amplitude are interpreted as demonstrating a developmental dissociation between the underlying M and P pathways, suggesting that the former is functional earlier and matures faster than the latter during the first year of life.

Contrast Sensitivity↗