neural connections in children with autism

Reduced interest in social interactions, a hallmark of autism, is shown to be related to decreased neural connections in children with autism.

Autism spectrum disorder (ASD) is a developmental disorder that affects a significant portion of the population.  As much as one child in 59 is affected by this disorder, which causes difficulties in social interactions with others, repetitive behaviours, speech issues, and difficulties in understanding non-verbal cues.  Autism is often diagnosed when children are at or near school age, rather than when the symptoms start to develop, which reduces the chances of early intervention to help compensate for any issues caused by ASD.

While the behaviours associated with autism are well known and can be diagnosed with appropriate neuropsychological testing, the causes of the behaviours are still only vaguely known.  There is only a small portion of autism cases that have been shown to be caused by specific genetic changes in DNA.  The rest seem to involve complex interactions between multiple genetic factors as well as the way the brain develops in the baby.  Changes seem to start even before the baby is born and affect how neurons (brain cells) connect with each other.

A neuron, the cell in our brains which allows us to sense, move, and think, has many branch-like structures that reach out and connect with other neurons within the brain.  It is these connections that generate our brain’s amazing abilities to talk, walk, feel, and think – much in the same way the connections on a computer chip allow a computer to do math, create graphics, and analyze data.

If a neuron’s ability to connect with others is affected, it might cause the neuron to over-connect (hyperconnectivity) or under-connect (hypoconnectivity) with other brain cells.  Since nerve cells communicate with each other through these connections, it means that parts of the brain that need to talk to each other are affected by these unusual connection patterns.  Such effects can cause many different observable brain disorders, including ASD.

The visual parts of the brain

One of the most recognizable symptoms of ASD is the lack of social awareness, where individuals with ASD cannot easily recognize emotions and non-verbal cues from another person. This makes it very hard for them to interact appropriately with others in social situations, making them seem awkward or disconnected from people.  It is most often associated with a lack of eye contact when interacting with other people.

Functional magnetic resonance imaging (fMRI) studies in adults have shown that there can be below-average connectivity between areas relevant to social interest and areas of the brain that control and interpret visual signals.  This can go a long way to explaining the social awkwardness associated with ASD.

However, there has been limited work done with very young children in this area, especially since it is harder to diagnose ASD in young children.  Some tests, which involve tracking eye movements and interests of toddlers and non-verbal babies, have shown some promise in helping to diagnose young children with ASD early on in their development.  Yet, there is very little information available about how the brains develop in very young children with ASD.

This is why a study recently published in the eLIFE journal has greatly improved our knowledge of this development by studying the neural connections in children with autism and without.  By looking at toddlers with a specific sub-type of ASD, they were able to find brain connectivity issues that correspond to levels of social difficulties experienced by the children.

Researchers used computer-assisted eye-tracking technology that monitors where a child is looking on a video screen.  They then played a split-screen video where one half showed various children playing, doing yoga, and interacting socially.  The other half of the screen showed moving geometric patterns.

One sub-type of ASD where children prefer looking at the geometric patterns rather than at the videos of children playing is called GeoPref ASD and affects about 20% of children with ASD.  When studying the brains of the GeoPref  ASD toddlers using fMRI as they were sleeping, researchers found that there were less signals between parts of the brain that involve social interest and parts of the brain that control and analyze vision than in typically developing children and even other children with ASD who don’t have GeoPref.

This drop in signals showed that there is a hypoconnectivity, or lack of connections, between these two centres, which could explain why GeoPref children tend to have worse scores on social interaction tests, and tend to have more difficulties interacting with their peers than even other children with non-GeoPref ASD.

Since there is a clear lack of connection between the social and visual brain centres, it also means that it may be possible to predict which children will develop GeoPref ASD symptoms by doing a simple, non-invasive brain imaging test.  This would allow for earlier diagnosing of ASD by analyzing the neural networks of children with autism symptoms.  That would then allow medical professionals to prepare an early intervention plan.   Such plans could include tailored help to try and improve connectivity between these brain centres that have difficulties communicating with each other.  And the earlier we can intervene with children with ASD, the more we can reduce the symptoms that affect them as they grow.

This new research has exciting possibilities, and the researchers are already working on collaborations for clinical testing, which means that this new method to help diagnose ASD by looking at the neural connections in children with autism, even in those as young as toddlers, may be just around the corner.

 

Written by Nancy Lemieux

 

References:

Lombardo, M., & et al. (2019). Default mode-visual network hypoconnectivity in an autism subtype with pronounced social visual engagement difficulties. Retrieved 20 December 2019, from https://elifesciences.org/articles/47427

In some children with autism, ‘social’ and ‘visual’ neural circuits don’t quite connect. (2019). Retrieved 20 December 2019, from https://www.eurekalert.org/pub_releases/2019-12/uoc–isc121719.php

What Is Autism? | Autism Speaks. (2019). Retrieved 20 December 2019, from https://www.autismspeaks.org/what-autism

Image by Colin Behrens from Pixabay

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