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Dravet syndrome (DS) is an epilepsy of infantile onset, usually related to a mutation in gene sodium channel alpha 1 subunit, that leads to different typological seizures before the first year of life. Although most research has focused on the clinical description of the syndrome, some recent studies have focused on its impact on cognitive development, identifying both motor disorders and visual-processing deficits as basic factors affected in adults and children with DS. In this article, we designed a cross-sectional study to examine the cognitive phenotype of children affected by DS from a neurodevelopmental perspective. We report measures for both basic (auditory perception, visual and phonological processing, motor coordination) and higher order cognitive processes (verbal production, categorization, and executive function) in two age groups of DS children (M = 8.8 and M = 14.1) and control children of the same chronological age. Results showed an important cognitive delay in DS children with respect to controls in both basic and higher order cognitive abilities, with a better general outcome in tasks that required processing visual material (visual memory and categorization) than in tasks involving verbal material. In addition, performance of DS children in certain basic tasks (visual memory) correlated with performance on complex ones (categorization). These findings encourage promoting an early identification of not only clinical but also cognitive features in DS children from very early stages of development in order to optimize their neurodevelopmental outcome.

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Words and morphemes are understood very quickly, but there are few techniques available to study the brain's response to them at the time-scale at which they occur. The left anterior negativity (LAN) has been reported as the primary ERP signature of morphosyntactic processing, but recent reports have questioned whether the LAN effect, in fact, exists, suggesting that it might result from component overlap during ERP averaging. Given that the LAN is relevant in sentence comprehension models, and that averaging procedure is widely used in ERP analysis, it becomes important to model the variability of this ERP effect. The present project examined whether the LAN effect, observed in the grand average response to local agreement violations in Spanish, is the result of the overlap between two different ERP effects (N400 and P600) at the level of subjects (n=80), items (n=120), or trials (n=6160).By-subject, by-item, and by-trial analyses of the gender violation effect between 300 ms and 500 ms showed a clear left-anterior negativity for 55% of the participants, 46% of the items, and 49% of the trials. Further analyses showed many examples of the biphasic LAN-P600 response. Mixed-linear models showed that the LAN effect size was not reduced after accounting for subject variability. The present results suggest that there are cases where the grand average LAN effect represents the brain responses of individual participants, items, and trials.