🧠 What brain waves reveal about the language of autistic children

Language development in autistic children is far from uniform: some progress without notable difficulty, while others show marked delays or barely speak. To better understand what is happening in their brains from an early age, scientists at the University of Geneva (UNIGE) analyzed the brain activity of autistic children and typically developing children aged 18 months to 6 years.

Their results, published in the journal Translational Psychiatry, show that the activity of certain brain waves evolves differently depending on the children's language abilities. This difference could serve as an early marker of language trajectories and enable early intervention.


Autism affects about 1 in 36 children, and language difficulties are among its most heterogeneous manifestations. "Understanding what differentiates the brain activity of an autistic child likely to develop fluent language from that of a child who will remain minimally verbal is a fundamental question both for research and for psychiatrists who follow these children and their families," explains Marie Schaer, professor in the Department of Psychiatry at the UNIGE Faculty of Medicine and lead investigator of this work.

Differences in gamma waves

To understand how language acquisition unfolds, the scientists followed 122 participants aged 18 months to 6 years from the Geneva cohort of autistic children — unique for the richness and precision of its clinical data — and 66 typically developing children. Using electroencephalograms — a non-invasive technique particularly well-suited for very young children — the scientists measured the brain's oscillatory activity in five frequency bands. During the recording, the children watched a cartoon of their choice to make the experience more comfortable.

Children with the greatest language difficulties showed the highest and most persistent gamma levels.

"Compared to typically developing children, autistic children showed increased brain activity in low frequencies—delta and theta waves—and in high frequencies—beta and gamma waves," details Kenza Latrèche, first author of the study and doctoral candidate in the Department of Psychiatry at the UNIGE Faculty of Medicine.

"But it is the gamma band, involved in information and language processing, that reveals the most significant differences: children with the greatest language difficulties showed the highest and most persistent gamma levels throughout development."

First sentences, a key milestone

A crucial moment in language development is the emergence, usually around 18 months, of the first word combinations, such as "open door." Gamma activity gradually increases before this stage, reaches a peak around the onset of first sentences, and then decreases.

"This phenomenon of decreasing brain excitation suggests that acquiring the ability to combine words reflects an important stage of brain development, after which information processing becomes more efficient and requires fewer resources," says Marie Schaer. "But in children with the greatest language difficulties, gamma activity remained high throughout development, without us observing this inflection point."

These results suggest that the brain implements dynamic mechanisms to support the emergence of language in young autistic children, with varying degrees of success depending on the case. Better understanding these brain trajectories could make it possible to identify children's specific needs earlier and offer personalized therapies at an age when they will be most effective.

This innovative work stems from multidisciplinary collaborations: the cohort of autistic children is constituted by teams from the Synapsy Center for research in psychiatric neurosciences for mental health, while the analyses on language development benefited from the expertise of the National Center of Competence in Research (NCCR) Evolving Language, notably through a collaboration with Valentina Borghesani, professor at the Faculty of Psychology and Educational Sciences at UNIGE.