A study published in the Cell Press journalCurrent Biology finds that people with autism spectrum disorder (ASD) do not make adjustments to their breaths (deep or short) based on good or bad smells.
It has previously been established that ASD is characterized by diminished sensory-motor coordination. The templates for sensory-motor coordination, called “Internal Action Models” or IAMs, are reported to be impaired in individuals with ASD. One of the IAMs for smell detection is sniff response. The research reported here works on the premise that sniff response requires fine adjustment of a motor function for an environmental cue and sets out to investigate whether this skill is somehow altered in ASD.
The researchers engaged 18 autistic and 18 control (normally developing) children for the study (17 boys and one girl in each group). The sniff response in children was measured using a computer-aided olfactometer that was able to deliver odors and measure airflow in the children’s noses. The children, whose average age was 7, were requested to sniff pleasant odors like shampoo or rose, as well as unpleasant odors like rotten fish or sour milk.
Analyses of results from the study showed:
- The sniff response was greatly altered in children with ASD.
- Whereas normally developing children were able to adjust their breathing within 305 milliseconds of smelling an odor, autistic children did not show this alteration in breathing.
- The more severe the autism disorder more pronounced the altered sniff response was.
- The aberrant sniff response in autistic children was based on social and not motor shortcomings.
- The test accuracy for diagnosis was 81% in children with or without a diagnosis of ASD.
The results are very significant since they give doctors a tool for diagnosing ASD in children fairly accurately, even in very young children.
Indeed, the senior author, Dr. Sobel, tells the American Association for Advancement of Science Public Release, "We can identify autism and its severity with meaningful accuracy within less than 10 minutes using a test that is completely non-verbal and entails no task to follow. This raises the hope that these findings could form the base for the development of a diagnostic tool that can be applied very early on, such as in toddlers only a few months old. Such early diagnosis would allow for more effective intervention."
Interestingly, soldiers with traumatic brain injury (TBI) were found to perform poorly in the smell test, owing to damage to the central nervous system. The damage was detected in the frontal and temporal lobes (involved in neurodegenerative disorders, Alzheimer’s disease, multiple sclerosis, and dementia) of the soldiers’ brains. These data, taken in combination with the current study, may indicate a crucial role for the human sense of smell as indicators of potential health issues.
Written by Mangala Sarkar, Ph.D.
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