Abstracts

Rationale: Although Febrile Seizures (FS) are considered benign, they have been associated with mild cognitive alterations. Studies suggest that longer FS duration may affect mechanisms underlying memory. As learning and memory are closely related, the aim of our study was to examine the link between FS duration and learning in infants. Repetition suppression (RS), the diminution of neuronal activity following stimuli repetition, can be used to study perceptual learning in infants. It has been little studied in FS, and a novel aspect of our study is the use of time-frequency (TF) analyses on EEG recordings in this population. It provides information on the activity for each frequency band, notably slow ones (i.e. Delta, Theta) which are predominant in infants. We hypothesize that FS duration will be negatively associated with learning as reflected through RS. Methods: EEG was recorded in 47 infants aged 11-26 months with a history of FS. Auditory RS was evaluated through a task composed of audio-visual stimuli of a woman or a man repeating the vowel “a” three times. Timeframes for each “a” were analyzed separately in the TF domain (Morlet decomposition). RS should lead to an increase in power following the presentation of the first “a” (a1) and a diminution in power following the second “a” (a2). Thus, RS was measured through the difference between a1 and a2 at the Cz region of interest (i.e. Electrodes 7, 31, 55, 80, and 108) for each frequency band of interest (i.e. Delta, Theta, Alpha 1 and 2, Beta 1 and 2, Gamma 1 and 2). Pearson bivariate correlations were conducted on FS duration and RS measures. Supplementary analyses were conducted to assess age as a potential confounding variable. Infants with insufficient epochs or missing FS duration values were excluded prior to analyses (n = 5). Results: The final sample was composed of 42 infants (18 males) with a mean age of 17.77 months at testing (SD = 4.26). TF maps for the Cz region of interest showed a positive activity following “a1”, whereas negative activity followed “a2”. All correlations between FS duration and frequency bands were negative. Correlation between RS and FS duration in the theta frequency band was found significant [r = -0.319, p = 0.040]. Conclusions: We showed that longer FS duration is associated with less RS following stimulus repetition, suggesting mechanisms underlying learning to be affected. Importantly, TF analyses revealed this relationship in slow frequencies, which have been associated with learning. Our results add to a body of literature showing longer FS duration to be associated with mild cognitive alterations. Future studies should focus on how these functional alterations may have an impact at the behavioral level. Funding: This work was supported by grants (Natural Sciences and Engineering Research Council of Canada, Fonds de Recherche du Québec Santé; FRQS) and a donation (Jean-Pierre Hogue Foundation) to Lippé, and scholarships to Thébault-Dagher from the Canadian Institutes of Health Research and the FRQS.