Why Autists Have Difficulty Recognizing and Interpreting Faces
Autism is classified as a pervasive developmental disorder. A cure for the disorder, which has a strong genetic basis and first appears during infancy or childhood, has not yet been found. Boys are four times more likely than girls to have autism. (source: shutterstock).
Autists may be able to recite bus timetables and movie showtimes. However, they find it difficult to recognize feelings such as happiness or sadness in other people. JARA-BRAIN junior professor Prof. Dr. Thomas Nickl-Jockschat and a team of researchers recently discovered that an anomaly in the visual centre is partly responsible for this deficit.
Patients with an autism spectrum disorder have difficulty reading social and emotional signals, for example. Their reactions are therefore often regarded as inappropriate: they speak in a monotone voice, and rarely use gestures or facial expressions. The reasons responsible for this behaviour have not been extensively investigated. JARA-BRAIN scientists have now been able to show that the impaired processing of visual information in autists is due to changed networks in the brain that help us to recognize and interpret faces.
Reduced activity in left fusiform gyrus.
In their meta-analysis, Prof. Thomas Nickl-Jockschat and his colleagues evaluated the results of 14 functional imaging studies. In the individual studies, autists were asked to fulfil different tasks, all of different tasks, all of which were related to the processing of faces, such as recognizing and describing faces, as well as interpreting their emotional expressions. “We were interested in the question of whether we would be able to identify systematic differences in the brain activity patterns of autists and healthy controls across studies,” says the JARA-BRAIN scientist. The result: “In all studies, we found that in autists, the left fusiform gyrus was less active when they processed faces.”
Further investigations, for which the researchers used data sets from the NKI Rockland Sample of the National Institute of Health (NIH) and the BrainMap database in San Antonio, showed that this less active region in the fusiform gyrus is part of a network responsible for recognizing and interpreting faces. The JARA-BRAIN scientists established a connection between this result and their earlier findings regarding structural abnormalities of brain regions in patients with autism spectrum disorders. Thomas Nickl-Jockschat: “We checked whether any of the five brain regions that are known to be affected by growth abnormalities are located within this network. Interestingly enough, this was only true for the brain region V5 in the occipital lobe, which can be found in close vicinity to the primary visual cortex.”
The researchers also found that in functional imaging studies concerning networks that correspond to the network of mirror neurons in humans, the brain region V5 played an important role. Mirror neurons are neurons in the brain that show the same activity patterns both when a person acts and when they observe the same action performed by another. There is therefore a connection between this network and processes that are associated with empathy. “The analysis revealed that the structural lesion in V5 in autists has very serious consequences for the fusiform network and the mirror neuron network – and therefore for face processing,” summarizes Thomas Nickl-Jockschat. The findings were recently published in the journal Brain Structure & Function.