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Autism Results in Impaired Aversion Response to Offensive Odors


Here is the abstract to a new piece of research that has revolutionary implications, if it can be confirmed.

“Internal action models (IAMs) are brain templates for sensory-motor coordination underlying diverse behaviors [ 1 ]. An emerging theory suggests that impaired IAMs are a common theme in autism spectrum disorder (ASD) [ 2–4 ]. However, whether impaired IAMs occur across sensory systems and how they relate to the major phenotype of ASD, namely impaired social communication [ 5 ], remains unclear. Olfaction relies on an IAM known as the sniff response, where sniff magnitude is automatically modulated to account for odor valence [ 6–12 ]. To test the failed IAM theory in olfaction, we precisely measured the non-verbal non-task-dependent sniff response concurrent with pleasant and unpleasant odors in 36 children—18 with ASD and 18 matched typically developing (TD) controls. We found that whereas TD children generated a typical adult-like sniff response within 305 ms of odor onset, ASD children had a profoundly altered sniff response, sniffing equally regardless of odor valance. This difference persisted despite equal reported odor perception and allowed for 81% correct ASD classification based on the sniff response alone (binomial, p < 0.001). Moreover, increasingly aberrant sniffing was associated with increasingly severe ASD (r = −0.75, p < 0.001), specifically with social (r = −0.72, p < 0.001), but not motor (r < −0.38, p > 0.18), impairment. These results uncover a novel ASD marker implying a mechanistic link between the underpinnings of olfaction and ASD and directly linking an impaired IAM with impaired social abilities.”

From Current Biology:

The research appears to show that autistic children do not respond to offensive odors normally.  Usually, a child who senses an unpleasant odor will stop sniffing.  Autistic children appear to continue to sniff for the same length of time, regardless of how pleasant or unpleasant the smell is; the persistence of sniffing appears to correlate with the severity of the autism, specifically social abnormalities.  This is a small study, only eighteen children and eighteen controls, but despite that, it shows a very strong correlation between autism and continued sniffing of unpleasant odors.  There should be no difficulty repeating this experiment, both formally and informally, with many more subjects, as it is a simple test which takes inexpensive equipment and only a couple of hours for each subject, with little likelihood of disturbing the experimental subjects; thus, experimental ethics review committees should have no qualms about allowing almost any subject to participate.

The dramatic findings and the need for a good test for autism that is nonverbal and requires no voluntary responses (that is, the subject merely watches a cartoon while spontaneously inhaling odors through a plastic nasal cannula that simultaneously measures depth and duration of inspiration) make it imperative and highly likely that this experiment will be replicated soon.  Informal replication could take only a few weeks in almost any child development laboratory.

If it works, this test will revolutionize the diagnosis of autism and pave the way for further advances in treatment and understanding of this serious and growing threat to child development.

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