Impact of Macrocephaly, as an Isolated Trait, on EEG Signal as Measured by Spectral Power and Multiscale Entropy during the First Year of Life.

Macrocephaly has been associated with neurodevelopmental disorders; however, it has been mainly studied in the context of pathological or high-risk populations and little is known about its impact, as an isolated trait, on brain development in general population. Electroencephalographic (EEG) power spectral density (PSD) and signal complexity have shown to be sensitive to neurodevelopment and its alterations. We aimed to investigate the impact of macrocephaly, as an isolated trait, on EEG signal as measured by PSD and multiscale entropy during the first year of life. We recorded high-density EEG resting-state activity of 74 healthy full-term infants, 50 control (26 girls), and 24 macrocephalic (12 girls) aged between 3 and 11 months. We used linear regression models to assess group and age effects on EEG PSD and signal complexity. Sex and brain volume measures, obtained via a 3D transfontanellar ultrasound, were also included into the models to evaluate their contribution. Our results showed lower PSD of the low alpha (8-10 Hz) frequency band and lower complexity in the macrocephalic group compared to the control group. In addition, we found an increase in low alpha (8.5-10 Hz) PSD and in the complexity index with age. These findings suggest that macrocephaly as an isolated trait has a significant impact on brain activity during the first year of life.

Developmental course of the repetition effect and change detection responses from infancy through childhood: a longitudinal study.

Neuronal repetition effect (repetition suppression and repetition enhancement) and change detection responses are fundamental brain responses that have implications in learning and cognitive development in infants and children. Studies have shown altered neuronal repetition and change detection responses in various clinical populations. However, the developmental course of these neuronal responses from infancy through childhood is still unknown. Using an electroencephalography oddball task, we investigate the developmental peculiarities of repetition effect and change detection responses in 43 children that we followed longitudinally from 3 months to 4 years of age. Analyses were conducted on theta (3-5 Hz), alpha (5-10 Hz), and beta (10-30 Hz) time-frequency windows. Results indicated that in the theta time-frequency window, in frontocentral and frontal regions of the brain, repetition and change detection responses followed a U-shaped pattern from 3 months to 4 years of age. Moreover, the change detection response was stronger in young infants compared to older children in frontocentral regions, regardless of the time-frequency window. Our findings add to the evidence of top-down modulation of perceptual systems in infants and children.

Infant repetition effects and change detection: Are they related to adaptive skills?

Repetition effects and change detection response have been proposed as neuro-electrophysiological correlates of fundamental learning processes. As such, they could be a good predictor of brain maturation and cognitive development. We recorded high density EEG in 71 healthy infants (32 females) aged between 3 and 9 months, while they listened to vowel sequences (standard /a/a/a/i/ [80%] and deviant /a/a/a/a/ [20%]). Adaptive skills, a surrogate of cognitive development, were measured via the parent form of the Adaptive Behavior Assessment System Second Edition (ABAS-II). Cortical auditory-evoked potentials (CAEPs) analyses, time-frequency analyses and a statistical approach using linear mixed models (LMMs) and linear regression models were performed. Age and adaptive skills were tested as predictors. Age modulation of repetition effects and change detection response was observed in theta (3-5 Hz), alpha (5-10 Hz) and high gamma (80-90 Hz) oscillations and in all CAEPs. Moreover, adaptive skills modulation of repetition effects was evidenced in theta (3-5 Hz), high gamma oscillations (80-90 Hz), N250/P350 peak-to-peak amplitude and P350 latency. Finally, adaptive skills modulation of change detection response was observed in the N250/P350 peak-to-peak amplitude. Our results confirm that repetition effects and change detection response evolve with age. Moreover, our results suggest that repetition effects and change detection response vary according to adaptive skills displayed by infants during the first year of life, demonstrating their predictive value for neurodevelopment.

Febrile seizures and increased stress sensitivity in children: How it relates to seizure characteristics.

BACKGROUND: Studies suggest that the relationship between seizures and stress starts early in life. However, evidence of long-term altered stress reactivity following early-life seizures is lacking. Our objectives were to assess alterations in stress hormone reactivity in children with past febrile seizures (FS) and investigate how these alterations relate to clinical characteristics. METHOD: This case-control study compared a convenience sample of children with simple FS (n = 24), complex FS (n = 18), and matched healthy controls (n = 42). Stress was induced by electrode placement for an electroencephalography (EEG) exam. Salivary cortisol to stress, using three samples collected before and after the stressor, was compared between groups and sex. The relationship between stress reactivity and clinical characteristics (i.e., FS duration, age at first FS, time since the last FS) was investigated. RESULTS: Cortisol reactivity to stress was significantly different depending on study groups, F(1, 78) = 6.415, p = 0.003, η2p = 0.141, but not sex nor was there a significant interaction between group and sex (p ≥ 0.581). Participants with simple FS showed higher cortisol reactivity to stress (M = 14.936, Standard deviation (SD) = 26.852) compared with those with complex FS (M = -4.663, SD = 18.649, p = 0.015) and controls (M = -3.817, SD = 18.907, p = 0.003). There was no significant difference between participants with complex FS and controls (p > 0.999). Stress reactivity was not linked to clinical characteristics. CONCLUSIONS: Children with past simple FS showed greater changes in salivary cortisol following stress, suggesting enhanced stress sensitivity. As similar results were not found in a population with complex FS, our study shows that stress alterations are not caused by seizure severity. Future studies are needed to investigate whether stress sensitivity may be premorbid to simple FS and may contribute to simple FS incidence.

EEG repetition and change detection responses in infancy predict adaptive functioning in preschool age: a longitudinal study.

Neurodevelopmental disorders (NDDs) are mostly diagnosed around the age of 4-5 years, which is too late considering that the brain is most susceptive to interventions during the first two years of life. Currently, diagnosis of NDDs is based on observed behaviors and symptoms, but identification of objective biomarkers would allow for earlier screening. In this longitudinal study, we investigated the relationship between repetition and change detection responses measured using an EEG oddball task during the first year of life and at two years of age, and cognitive abilities and adaptive functioning during preschool years (4 years old). Identification of early biomarkers is challenging given that there is a lot of variability in developmental courses among young infants. Therefore, the second aim of this study is to assess whether brain growth is a factor of interindividual variability that influences repetition and change detection responses. To obtain variability in brain growth beyond the normative range, infants with macrocephaly were included in our sample. Thus, 43 normocephalic children and 20 macrocephalic children were tested. Cognitive abilities at preschool age were assessed with the WPPSI-IV and adaptive functioning was measured with the ABAS-II. Time-frequency analyses were conducted on the EEG data. Results indicated that repetition and change detection responses in the first year of life predict adaptive functioning at 4 years of age, independently of head circumference. Moreover, our findings suggested that brain growth explains variability in neural responses mostly in the first years of life, so that macrocephalic children did not display repetition suppression responses, while normocephalic children did. This longitudinal study demonstrates that the first year of life is an important period for the early screening of children at risk of developing NDDs.

Impact of brain overgrowth on sensorial learning processing during the first year of life.

Macrocephaly is present in about 2-5% of the general population. It can be found as an isolated benign trait or as part of a syndromic condition. Brain overgrowth has been associated with neurodevelopmental disorders such as autism during the first year of life, however, evidence remains inconclusive. Furthermore, most of the studies have involved pathological or high-risk populations, but little is known about the effects of brain overgrowth on neurodevelopment in otherwise neurotypical infants. We investigated the impact of brain overgrowth on basic perceptual learning processes (repetition effects and change detection response) during the first year of life. We recorded high density electroencephalograms (EEG) in 116 full-term healthy infants aged between 3 and 11 months, 35 macrocephalic (14 girls) and 81 normocephalic (39 girls) classified according to the WHO head circumference norms. We used an adapted oddball paradigm, time-frequency analyses, and auditory event-related brain potentials (ERPs) to investigate differences between groups. We show that brain overgrowth has a significant impact on repetition effects and change detection response in the 10-20 Hz frequency band, and in N450 latency, suggesting that these correlates of sensorial learning processes are sensitive to brain overgrowth during the first year of life.

Effects of eight neuropsychiatric copy number variants on human brain structure.

Many copy number variants (CNVs) confer risk for the same range of neurodevelopmental symptoms and psychiatric conditions including autism and schizophrenia. Yet, to date neuroimaging studies have typically been carried out one mutation at a time, showing that CNVs have large effects on brain anatomy. Here, we aimed to characterize and quantify the distinct brain morphometry effects and latent dimensions across 8 neuropsychiatric CNVs. We analyzed T1-weighted MRI data from clinically and non-clinically ascertained CNV carriers (deletion/duplication) at the 1q21.1 (n = 39/28), 16p11.2 (n = 87/78), 22q11.2 (n = 75/30), and 15q11.2 (n = 72/76) loci as well as 1296 non-carriers (controls). Case-control contrasts of all examined genomic loci demonstrated effects on brain anatomy, with deletions and duplications showing mirror effects at the global and regional levels. Although CNVs mainly showed distinct brain patterns, principal component analysis (PCA) loaded subsets of CNVs on two latent brain dimensions, which explained 32 and 29% of the variance of the 8 Cohen's d maps. The cingulate gyrus, insula, supplementary motor cortex, and cerebellum were identified by PCA and multi-view pattern learning as top regions contributing to latent dimension shared across subsets of CNVs. The large proportion of distinct CNV effects on brain morphology may explain the small neuroimaging effect sizes reported in polygenic psychiatric conditions. Nevertheless, latent gene brain morphology dimensions will help subgroup the rapidly expanding landscape of neuropsychiatric variants and dissect the heterogeneity of idiopathic conditions.

Prolonged and unprolonged complex febrile seizures differently affect frontal theta brain activity.

OBJECTIVE: Studies have identified mild but persistent cognitive and functional deficits, which could be linked to each other, in children with complex febrile seizures (FS). Our aim was to investigate differences in brain activity in children with a history of complex FS, through a study paradigm notably associated with the development of learning capacities and using electroencephalographic (EEG) signal. To further increase our understanding of these differences, complex FS were studied separately depending on their type. METHOD: EEG was recorded in 43 children with past FS. Brain activity associated with auditory learning was investigated using a habituation paradigm, in which repetition suppression (RS) is typically found following stimulus repetition. Auditory stimuli were repeated three times, and each presentation were analysed separately in the time-frequency (TF) domain. A mixed-analysis of variance was used to assess differences in spectral power between stimulus repetition and FS type (simple vs complex prolonged; CP vs complex unprolonged; CUP). RESULTS: Repetition effects were found in the 3-6 Hz during 150-600 ms time window after stimulus onset at frontal sites (F(2, 40) = 5.645, p = 0.007, η2p = 0.220). Moreover, an interaction effect between stimulus repetition and FS type (F(4, 80) = 2.607, p = 0.042, η2p = 0.115) was found. Children with CP FS showed greater increase in spectral power in response to the first stimulus presentation, while children with CUP FS failed to show a RS pattern. SIGNIFICANCE: Our results show distinct abnormalities in brain activity to a habituation paradigm. We argue that these changes suggest children with CP FS may be hyperexcitable, while children with CUP FS show impaired habituation processes. Still, these differences may be associated with other clinical features linked to complex FS as well. Hence, the role of these differences in complex FS incidence and prognosis should be the subject of future studies.

The relationship between acute stress and EEG repetition suppression in infants.

Over activation of the hypothalamo-pituitary-adrenal (HPA) axis in stress situations is known to influence learning and memory. In adults, an inverted-U shape relationship between acute stress, and learning and memory has been demonstrated. Whether this model fits learning performances in infants is unknown. In this study, we used EEG repetition suppression as physiological measure of learning and salivary cortisol in response to a stressor to investigate the relationship between acute stress and learning in infants. We hypothesized that EEG repetition suppression would be modulated by acute stress following an inverted-U shape relationship. Saliva samples were collected during an EEG experiment before, during and after EEG net installation in 37 healthy infants (18 males) aged between 6 and 26 months. The effect of variation in stress hormones on repetition suppression were modeled using a linear mixed model, with cortisol, age and sex as predictors. Results indicated that in healthy infants, elevations in stress hormones within the normal range are associated with a higher repetition suppression response and an increased response to the first presentation of the stimulus. The later increase could be related to vigilance. Considering that early childhood is a critical period of development, future studies should keep investigating the influence of stress on learning processes in infants.