Children with autism process auditory information differently.

The results of the work are published in the journal Brain Structure and Function. Autism Spectrum Disorders (ASD) are a group of pathological conditions caused by the developmental features of the brain that can affect communication skills and social behavior. Children with ASD often have accompanying speech disorders, which can range from speech deficits to a complete inability to speak.

The causes of speech disorders in ASD are still not well understood. Researchers believe that the neurobiological mechanisms underlying autism involve an imbalance between excitatory and inhibitory processes in the brain's cortex, which are determined by the oscillations of brain nerve cells. These oscillations produce weak but noticeable electromagnetic signals (for example, alpha, beta, and gamma rhythms) that can be recorded using magnetoencephalography (MEG).

An international team of researchers, including scientists from the Language and Brain Center at HSE University, studied alpha rhythm oscillations (markers of excitability) in children with autism. Alpha rhythms play a crucial role in processing sensory information and maintaining attention, such as when perceiving auditory information.

The scientists investigated how sound perception in children with ASD is related to speech disorders. To do this, they measured brain activity in 20 children with varying degrees of autism and 20 typical children using magnetoencephalography. All participants underwent clinical and behavioral speech assessments, tests for non-verbal intelligence (IQ), and evaluations of autistic traits. Speech skills were measured using the "Boat" test. During the MEG, participants were presented with auditory stimuli while their brain activity was monitored, with no special actions required from the subjects. The experimenters observed the fluctuations of alpha rhythms both at rest and during the processing of the presented auditory signals.

It turned out that children with autism exhibited disrupted levels of alpha rhythms both when perceiving auditory information and at rest. Normally, during sound processing, the auditory cortex experiences a significant decrease in alpha wave power, whereas during rest, it increases. In children with autism, the opposite pattern was observed.

“The weak decrease in alpha rhythm power during auditory information processing in children with autism indicates increased excitability of neural networks in the auditory cortex and confirms the presence of an imbalance between excitation and inhibition in the brain's cortex,” explains Vardan Arutyunyan, one of the study's authors and a research associate at the Seattle Children's Research Institute (USA).

The authors of the article also identified a connection between brain activity at rest in the left auditory cortex and the language abilities of children with ASD. The researchers transformed the complex and multidimensional MEG signal into a set of parameters, analyzed them, and determined that one of the components of the signal (offset), which reflects the average frequency of neural firings, is associated with speech skills. The higher this parameter (and, correspondingly, the greater the neural excitability at rest in the left auditory cortex), the poorer the speech skills of children with ASD.

“We analyzed all the data collected during the experiment: the MEG results, IQ tests, and assessments of the severity of autistic traits and speech skills. It turned out that children with more impaired neural processes in the left hemisphere exhibited poorer language abilities. We observed that in autism, impairments are present even at the early stages of information processing in the auditory cortex, which may reflect on higher-level processes such as speech,” says Olga Drago, director of the Language and Brain Center at HSE University.
The study's findings contribute to a better understanding of the causes of speech disorders in autism spectrum disorders and can help in developing methods for their correction in the future.