– What causes autism?
— Many theories have been put forward regarding the origin of autism. It was once thought that autism might be the result of a defect in a particular brain structure or connections between the hemispheres. However, it later became clear that this was not the case, because no single disorder was found in people with autism. The disorder may be the result of a number of disorders that cause similar symptoms. For this reason, it is now common to say “autism spectrum disorder” (ASD) rather than “autism”.
— So, could different children with ASD have different pathologies in brain development?
– Yes. ASD is a highly heterogeneous developmental disorder. This means that many completely different causes can lead to similar symptoms – disruption of social communication, communication and the emergence of repetitive behavior. For example, you have a fever, you don’t know why. This could be a virus, bacteria, stress, allergies or overheating in the sun. It has many causes but only one symptom. In people with ASD, this symptom is not fever, but behavioral disorder.
— It turns out that there is no specific difference between the brains of children with ASD and the brains of normally developing children.
— Let’s put it this way: If you send a child with autism to an MRI, the doctor will most likely find nothing there, no specific pathology. Of course, there are also types of autism where something is visible to the eye. But in most cases, MRI is useless because the disorder often does not lead to changes in the macrostructure of the brain. This may be a malfunction in connections not seen on MRI.
— So scientists don’t know at all what kinds of disorders in brain function lead to the development of ASD?
— Today, the main neurophysiological theory of autism is an imbalance in the functioning of certain types of nerve cells in the brain. There are excitatory neurons and inhibitory neurons in the brain that regulate their activity. This balance between the activity of excitatory and inhibitory neurons is crucial for brain development and normal functioning. If it is impaired, brain function is also impaired. However, the interesting thing is that each individual with autism differs from the norm in his or her own way. They are all different not only from us, but also from each other.
— What methods allow us to study the disruption of this balance?
“If we are dealing with animal models of autism, this balance can be assessed ‘invasively’, that is, using electrodes placed in the brain. This of course cannot be done to humans, other methods are needed.”
We studied children with ASD and neurotypical school-age children using magnetic encephalography (MEG). The only MEG device in the country is located at Moscow Psychological and Pedagogical University (MGPPU). Like the more common method of electroencephalography (EEG), MEG allows you to study brain activity “non-invasively”, that is, without entering the brain, and has a number of important advantages.
– Which ones?
“Especially with the help of MEG, it is possible to “localize” the sources of brain activity quite accurately. We looked at activity measurement, which is thought to reflect an imbalance of excitatory and inhibitory activity in children with ASD. Of course, with MEG, we do not see each brain cell one by one, but we can evaluate their total activity.
The results showed that a shift in balance towards arousal in autism was observed only in children with reduced intelligence. In fact, this is not surprising, because epilepsy (epilepsy occurs due to excessive nervous discharge in the cerebral cortex – socialbites.ca) is much more common in people with severe cases of autism, aggravated by mental disability.
— What does information tell us in which direction the change in the excitation-inhibition balance is directed in a child with ASD?
“This is a type of biomarker that can be used for diagnosis and selection of the necessary treatment. For example, if we test the effect of a drug, we will be able to measure this change before and after the start of treatment. This can help in the selection of individual drugs. But you need to be careful because you cannot draw conclusions based on a single study.
— What causes this balance to be disrupted? Genes?
– Basically yes. Autism is determined by genes at a rate of 70-90%. But there are hundreds of genes that have been associated with autism to some degree. Although they have different functions, their disorders somehow affect the functioning of certain functional brain networks important for social behavior and communication. Many of the genes associated with autism start working even before the child is born, during the first and second trimesters when the fetus is forming. They are associated with neurogenesis (the development of nerve cells in the brain).
—Scientists at Cold Spring Harbor Laboratory in New York I learnedIt turns out that children with autism inherit most of their genome from their fathers rather than their mothers. Does such a model really exist?
“According to the scientific literature, there is no clear pattern as to who autism-related genes are most frequently inherited from. For most forms of autism, this is a cumulative effect from both mother and father. But there are certain forms in which genes from one of the parents play a large role. Such a form is usually Fragile
— Could it be that the fetus has “autism genes” but they are not activated?
– Definitely. Many of us have genes associated with autism. ASD develops when a certain number of such genes accumulate or become “knocked out” in a certain combination.
However, since the contribution of genetic factors is not 100%, it is important to consider environmental factors as well. For example, prematurity, taking certain medications or an infectious disease during pregnancy. It can also have negative effects. If genetic load is added to these factors, the risk of developing ASD in the child increases.
— You are currently working on auditory speech disorders in autism. Why do they occur, and in which brain structure is the work disrupted?
— Speech delay is one of the first nonspecific symptoms of autism. Speech development in most children with ASD develops after age three, and this is still not very accurate, and disorders can affect several levels: phonology, syntax, semantics, and pragmatics. Approximately 30% of children with ASD speak little or not at all.
There are two main hypotheses here, which are not mutually exclusive. Firstly, speech disorders are a consequence of social problems, decreased interest in communication and contact with people. Second, it suggests that speech impairment, at least in some children with ASD, may be related to impaired processing of complex auditory signals.
—What specific sound processing disorders are seen in children with ASD?
– From the cochlea, sound information passes through many intermediate stations in the brainstem and thalamus and enters the cerebral cortex. Speech perception impairment may be associated with signal processing impairment at one or more stages of this pathway. A child’s hearing may be normal based on routine audiometric testing, but he or she may have difficulty extracting information from what they hear. This is especially noticeable in noisy environments.
This auditory processing disorder puts the child at a disadvantage relative to their peers and creates additional difficulties in learning and communication. Examining auditory processing disorders is important because they can be corrected. For example, we are currently investigating how the brains of children with ASD process vowels.
— Why are you studying vowel sounds?
— Vowels are the first sounds that the child begins to pronounce. They are even more important than consonants for understanding speech. During the experiment, children watch silent cartoons while sounds (vowels, modified vowels, and control sound) are played through headphones. We compared how children’s brains process vowels and control sounds. The brains of neurotypical children quickly distinguish vowels from noise, but children with autism have reduced response to vowels. Moreover, interestingly, this decline is also linked to the results of behavioral tests. However, these are preliminary results.
— What is its relationship with behavior?
“The less the brains of children with ASD respond to vowels, the worse their perception of speech in noise becomes. In general, many people with ASD experience a sharp impairment in the perception of speech in the background of noise. This is the so-called “cocktail party” syndrome. So you come to a noisy place and you can hear your interlocutor well despite the surrounding noise. It is difficult for a person with ASD to follow a conversation in this state because it is difficult for him to separate speech from noise.
At our center, we conducted a purely behavioral study in which we allowed children to listen to words against a background of noise. It turns out that children with autism have much more difficulty hearing noisy speech, regardless of their level of mental development. Children with ASD frequently repeated word fragments but were unable to put them together into a single whole.
– Why is this happening?
“We’re not sure, but one of the reasons may be poor performance of the attention-switching system.” A few years ago we conducted a study that confirmed this hypothesis. We showed the child a cartoon and made a few loud clicks from time to time. It turns out that in children with ASD, the response to the first unexpected click is reduced, especially in the right hemisphere, which is known to be important for shifting attention.
The structures within the “right hemisphere” system that enable attention shifting are also important in terms of social communication. This relay system comes into play when we communicate because we need to quickly monitor and react to the other person’s behavior. We hypothesize that impairments in this system may be associated with impairments in social skills in ASD. However, more research is needed; It is difficult to draw definitive conclusions.
— You said that these auditory-speech disorders can be corrected. How?
— There are two main groups of methods. The first is listening training, as in learning a foreign language. Various game programs are used here. A second highly effective method that can help children suffering from auditory processing disorders is the remote microphone system. The microphone is placed near the speaker’s mouth (for example, attached to the teacher’s or parent’s clothing), and the child wears a signal amplification device that is either built into an “open-type” hearing aid or connected to headphones. This signal amplification improves speech understanding.
Research has shown that such systems with remote microphones are also beneficial for children with dyslexia, who often also suffer from auditory processing disorders. Moreover, it has been shown that long-term use of such a device leads to sustainable plastic changes in the brain. So, we see positive dynamics not only while the child is using this assistive device, but also after it is finished.
— Is this technique used in Russia?
— Unfortunately, this method is not yet used in Russia. At the Federal Resource Center of the Moscow State University of Psychology and Education, where children with ASD study, a study on the effectiveness of home systems with external microphones is being conducted. We also study the mechanisms of auditory-speech disorders in children with autism at the MEG center of the Moscow State University of Psychology and Education.
We hope that these studies will provide practical benefits. Therefore, we invite all interested parents of boys between the ages of 7 and 12 to come to us and participate in the studies. We hope that our research will help improve the quality of life of children with ASD.