Tuesday, March 27, 2012

"Higher Perceptual Capacity" or Malfunctioning Senses?

In light of the bit of nonsense I talked about a few days back, I thought I would point out this new study on sensory input in people with autism.  This new study demonstrates yet again that people with autism can have actual physical differences in how they respond to sensory stimuli.

So far from a "they experience everything" model, this paper takes us back to accepted - and somewhat proven - idea that people with autism experience sensory stimuli differently than a "typical" person does and these differences might account for some of the disabling symptoms of autism.

The abstract is below ( I added line breaks to make it more readable) -
Perceptual and Neural Response to Affective Tactile Texture Stimulation in Adults with Autism Spectrum Disorders.
Autism spectrum disorders (ASD) are associated with differences in sensory sensitivity and affective response to sensory stimuli, the neural basis of which is still largely unknown. We used psychophysics and functional magnetic resonance imaging (fMRI) to investigate responses to somatosensory stimulation with three textured surfaces that spanned a range of roughness and pleasantness in a sample of adults with ASD and a control group. 
While psychophysical ratings of roughness and pleasantness were largely similar across the two groups, the ASD group gave pleasant and unpleasant textures more extreme average ratings than did controls. In addition, their ratings for a neutral texture were more variable than controls, indicating they are less consistent in evaluating a stimulus that is affectively ambiguous. 
Changes in brain blood oxygenation level-dependent (BOLD) signal in response to stimulation with these textures differed substantially between the groups, with the ASD group exhibiting diminished responses compared to the control group, particularly for pleasant and neutral textures. For the most unpleasant texture, the ASD group exhibited greater BOLD response than controls in affective somatosensory processing areas such as the posterior cingulate cortex and the insula. The amplitude of response in the insula in response to the unpleasant texture was positively correlated with social impairment as measured by the Autism Diagnostic Interview-Revised (ADI-R). 
These results suggest that people with ASD tend to show diminished response to pleasant and neutral stimuli, and exaggerated limbic responses to unpleasant stimuli, which may contribute to diminished social reward associated with touch, perpetuating social withdrawal, and aberrant social development.

Reference :

Cascio CJ, Moana-Filho EJ, Guest S, Nebel MB, Weisner J, Baranek GT, Essick GK. Perceptual and Neural Response to Affective Tactile Texture Stimulation in Adults with Autism Spectrum Disorders. Autism Res. 2012 Mar 23. doi: 10.1002/aur.1224. [Epub ahead of print] PubMed PMID: 22447729.


  1. There was a much greater emphasis on atypical sensory response when my son was younger (late 90's). I'm glad to see this.

  2. Still at a loss as to why increased sensitivity and higher perceptual capacity aren't the synonyms they appear to be.

    1. I'm not sure I am following what you are saying.

      The point is that attempting to rebrand the sensory issues in autism as some sort of higher processing capacity is not supported by the available evidence.

      As in there is no real evidence that sensory issues are caused by too much processing capacity while there is plenty of evidence, such as the study in the post, that there are filtering, processing, and abnormal response issues.

    2. I don't think "caused by" makes much sense. If you have sensory issues you'll have perceptual issues - it's just a different way of looking at it depending on the model you're using. For example, if you want to talk about autistics finding certain textures painful refer to senses, but if you want to talk about fluid intelligence then refer to perception.

  3. That only pain registers would account for why my son doesn't want to be touched unless he knows it is coming: he can prepare for it. You don't know if it will be the type of touch that registers as a "zap" or not.

    How could we go so long without realizing when autistics said it was painful to be touched....This is a ridiculous comparison, but perhaps the skin registers a short circuit to the brain, a sensorial epilepsy.