Children with Autism Process Auditory Information Differently
A team of scientists, including researchers from the HSE Centre for Language and Brain, examined specific aspects of auditory perception in children with autism. The scientists observed atypical alpha rhythm activity both during sound perception and at rest. This suggests that these children experience abnormalities in the early stages of sound processing in the brain's auditory cortex. Over time, these abnormalities can result in language difficulties. The study findings have been published in Brain Structure and Function.
Autism spectrum disorders (ASD) are a group of conditions caused by abnormalities in brain development that can affect communication skills and social behaviour. Children with ASD often experience co-occurring language impairments, ranging from mild language deficits to a complete inability to speak.
The causes of language impairment in ASD are not yet well understood. Researchers believe that the neurobiological mechanisms of autism stem from an imbalance between excitatory and inhibitory processes in the cerebral cortex, driven by oscillations of nerve cells in the brain. These oscillations produce weak but detectable electromagnetic signals, such as alpha, beta, and gamma rhythms, which can be measured using magnetoencephalography (MEG).
An international team of researchers, including scientists from the HSE Centre for Language and Brain, studied alpha rhythm oscillations (markers of excitability) in children with autism. Alpha rhythms play a key role in processing sensory information and maintaining attention, eg during auditory perception.
The scientists explored the relationship between sound perception and language impairment in children with ASD. To achieve this, they used magnetoencephalography to measure brain activity in 20 children with autism of varying severity and in 20 typically developing controls. All study participants underwent clinical and behavioural language assessments, as well as tests for nonverbal intelligence (IQ) and the severity of autistic traits. Their language skills were measured using RuCLAB (Russian Child Language Assessment Battery). During the MEG, participants were presented with sound stimuli while their brain activity was measured, requiring no special actions from them. The authors of the experiment monitored alpha oscillations both at rest and during the processing of presented audio signals.
It was found that children with autism exhibit impaired alpha rhythms both during auditory perception and at rest. Typically, when sounds are processed in the auditory cortex, the power of alpha waves decreases significantly, while it increases during rest. The opposite pattern was observed in children with autism.
'A slight decrease in alpha rhythm power during auditory information processing in children with autism indicates increased excitability of neural networks in the auditory cortex, confirming an imbalance between excitation and inhibition in the cerebral cortex,' explains Vardan Arutiunian, co-author of the study and research fellow at the Seattle Children's Research Institute, USA.
The authors of the paper also found a link between brain activity at rest in the left auditory cortex and the language abilities of children with ASD. The researchers converted the complex, multidimensional MEG signals into a set of parameters, analysed them, and discovered that one component of the signal (offset), which reflects the average frequency of neural discharges, is associated with language skills. The higher this parameter (and consequently, the greater the resting neural excitability in the left auditory cortex), the poorer the language skills of children with ASD.
Olga Dragoy
'We analysed all the data collected during the experiment, including the MEG results, IQ tests, and assessments of autistic traits and language skills. It was found that children with more impaired neural processes in the left hemisphere exhibited poorer language abilities. We observed that in autism, abnormalities are present at the early stages of information processing in the auditory cortex, which can impact higher-level processes such as language,' according to Olga Dragoy, Director of the HSE Centre for Language and Brain.
The study's findings can lead to a better understanding of the causes of language impairment in autism spectrum disorders and contribute to the development of corrective interventions.