Altered visual evoked potentials associated with verbal and nonverbal skills in Fragile X syndrome.

BackgroundUnderstanding the neurobiology behind Fragile X syndrome (FXS) is critical in identifying effective therapeutics and improving care for affected individuals. Electroencephalography (EEG) provides an opportunity to investigate the biological foundations of this disorder. We aimed to characterize the visual evoked potential (VEP) in young children with FXS, and to understand how measures of the VEP are associated with verbal and nonverbal development within FXS. MethodsVEPs were collected in children between 2-7 years old with FXS (n = 9) as well as corresponding age-(n = 10) and cognitive-matched (n = 9) typically developing children. Additionally, the Mullen Scales of Early Learning and Preschool Language Scales were administered to collect measures of verbal and nonverbal development. Differences in component amplitudes and latencies of the VEP were assessed using ANCOVAs, and associations of VEP measures and verbal and nonverbal development were evaluated using linear regression with age as a covariate. ResultsNo differences between groups were observed in N1, P1, or N2 VEP components. However, a consistent and prominent P2 component (latency = 177ms {+/-} 13.7), was observed in children with FXS. The P2 amplitude was significantly increased in FXS children compared to the cognitive-matched group (p = 0.004). For children with FXS, the amplitude of several VEP components were associated with verbal and nonverbal development; larger N1 amplitude and smaller P1 and P2 amplitudes were all associated with better receptive language (all p<0.05) and larger N1 amplitude was also associated with better fine motor skills (p<0.05). ConclusionsThe observed increase in P2 amplitude and its negative association with language development within the FXS group supports the P2 component as a potential biomarker for FXS as a disorder, as well as a pathophysiological marker of verbal impairment that could be used in clinical trials.