There is a reason that a puzzle piece is the symbol of autism spectrum disorder (ASD). Despite all the research, despite the advances, ASD continues to be an enigma. What causes it? Can it be diagnosed earlier? What are the differences between an autistic and a neurotypical brain?
One field of research – the role of the sense of smell – is producing surprising results that could lead to means of early diagnosis and intervention, as well as shed light on the misreading of social cues that is so common in autism.
Prof. Noam Sobel, who heads the Weizmann Institute’s Department of Neurobiology, studies the olfactory system. The sense of smell is our earliest and most ancient one, and his work has shown that it’s involved in a surprising number of subconscious responses and tells us a great deal about how our brains have evolved. And now, he’s found that children with ASD respond to smells differently than neurotypical ones – a breakthrough that could lead to a way to diagnose the condition early.
The children in the study – a mix of kids with autism and neurotypical ones – were exposed to a range of smells, both pleasant and unpleasant. Neurotypical persons breathe in deeply in response to a pleasant odor and, likewise, breathe shallowly when something smells bad. Sobel lab member Liron Rozenkrantz said that “this activity is controlled, in part, by the cerebellum, which also plays a role in autism.”
But, notably, the children with autism had a different response: they did not modify their breathing. The more severe the autism, the more atypical the sniffing response, showing up as a longer inhale in response to an unpleasant odor. This variance allowed the researchers to ascertain with 81% accuracy whether a child was autistic.
Because the test does not require either the use of language or particularly high cognitive skills, the scientists hope that in the future it may be used to assist in the diagnosis of autism at an earlier age than is possible today.
In another line of research, Prof. Sobel and his team set out to test whether, like other forms of social communication, emotional response to odor is disrupted in the case of autism. It has long been known that certain emotions – including happiness and aggression – are associated with specific smells produced by the body, and that people respond to such odors, even if they are not consciously aware of the smell.
Working with two groups – high-functioning autistic people and a control group without ASD – the scientists exposed their subjects to the smell of fear. (As The Independent reports, the “smell of fear” was sweat taken from skydivers.)
The results: the non-autistic group responded as you’d expect – the fear-induced sweat lead to a fearful response. The ASD group, on the other hand, responded in the opposite manner: fear-induced sweat lowered their fear responses. In fact, in a parallel test, the odor of “calm sweat” actually raised their anxiety levels.
Further studies using mannequins also showed opposite responses: ASD participants placed more trust in a mannequin that had a fear smell, and were more wary of one with a calm smell.
These results provide a biological basis for a trait often seen in autistic persons: misreading of social cues. Prof. Sobel, quoted in Scientific American, said that “I think this could be a meaningful aspect of impaired social interaction … Humans constantly engage in social chemo-signaling; we do this all the time, and it shapes our interactions. And somehow these mechanisms work differently in autism.”
