Autism not just a disease of the brain: Study

Autism, which significantly impairs an individual's ability to communicate as well as interact socially, has also been found to impact their senses, says a new study.

The findings showed that at least some aspects of autism spectrum disorder (ASD) -- including how touch is perceived, anxiety and social abnormalities -- are linked to defects in another area of the nervous system -- the peripheral nerves found throughout the limbs and other parts of the body that communicate sensory information to the brain.

"An underlying assumption has been that ASD is solely a disease of the brain, but we've found that may not always be the case," said David Ginty, Professor at Harvard Medical School.

For the study, the researchers genetically engineered mice that have gene mutations only in their peripheral sensory neurons, which has the potential to detect light touch stimuli acting on the skin. 

The researches measured how the mice reacted to touch stimuli, such as a light puff of air on their backs and tested whether they could discriminate between objects with different textures.

The results revealed that mice with ASD gene mutations in only their sensory neurons exhibited heightened sensitivity to touch stimuli and were unable to discriminate between textures. 

The transmission of neural impulses between the touch-sensitive neurons in the skin and the spinal cord neurons that relay touch signals to the brain were also found abnormal in them.

Together, these results, published in the journal Cell, showed that mice with ASD-associated gene mutations have deficits in tactile perception.

"Advances in mouse genetics have made it possible for us to study genes linked to ASD by altering them only in certain types of nerve cells and studying the effects," added Ginty, who is also, Investigator at Howard Hughes Medical Institute, in the US.

They next examined anxiety and social interactions in the mice using established tests looking at how much mice avoided being out in the open and how much they interacted with mice they'd never seen before. 

Surprisingly, the animals with ASD gene mutations only in peripheral sensory neurons showed heightened anxiety and interacted less with other mice. 

"A key aspect of this work is that we've shown that a tactile, somatosensory dysfunction contributes to behavioural deficits, something that hasn't been seen before," Ginty says. "In this case, that deficit is anxiety and problems with social interactions."