NIR spectroscopy could help to diagnose autism

Japanese researchers have added to the growing body of evidence suggesting that NIR spectroscopy can help to diagnose children with autism spectrum disorder (ASD), which is characterised by various problems with social interaction and communication.

Studies with neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have demonstrated impaired activity in certain areas of the brains of those with ASD. These areas include the medial prefrontal cortex (MPFC), which is known to be involved in attributing an independent mental state to self and others.

More recently, two research groups have shown that this impaired brain activity in ASD patients can also be detected by NIR spectroscopy, based on changes in the concentration of oxygenated haemoglobin, when performing specific tasks. Because NIR spectroscopy is simpler to conduct and requires less bulky equipment than fMRI or PET, this opens up the possibility of using it in the clinic for diagnosing ASD, even with children.

Confirming this potential, researchers from the Nagasaki University Graduate School of Biomedical Science in Japan have now used NIR spectroscopy to detect impaired activity in the MPFC of children with ASD when trying to infer the mental states of others. They attached 15 NIR probes to the temples of 32 children aged between eight and 14, half of whom had ASD, and then monitored the concentration of oxygenated haemoglobin in the MPFC as they performed two tasks.

In one task, the children were asked to describe the mental state of a person, whether angry, happy or neutral, from photos of their eyes. In the other task, they were shown photos of three objects (a truck, a flower and a church) and asked to describe their physical characteristics.

As the researchers report in Psychiatry and Clinical Neurosciences, the children with ASD were more likely than the other children to refer to non-emotional aspects of the images of a person's eyes, as has been found in other studies. What NIR spectroscopy also revealed was that this is associated with a lower level of activity in the MPFC of children with ASD compared with the other children. In contrast, there was a similar level of activity in both groups of children when looking at photos of the three objects.

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