Scientists from Western University (Canada), led by Matthew Kolisynik and Ryan Stevenson, have found that different types of sensory perception in autistic children correspond to different patterns of connectivity between brain regions. The work was published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
It is known that up to 87% of people with autism respond unusually to external stimuli: some sounds, smells or touches may seem too intense to them, while others may be almost imperceptible. Some actively seek out strong sensations, while others try to avoid everyday stimuli. In a previous large study, scientists identified five sensory profiles (stable types of reactions) in autistic youth: adaptive (minimal differences from neurotypical peers), generalized sensory differences (severe reactions in almost all areas), as well as three narrower profiles - with selective sensitivity to taste and smell, with reduced reactivity combined with sensation seeking, and with motor difficulties and low energy.
The new work involved 146 autistic children and adolescents. Their caregivers completed standard questionnaires about everyday sensory reactions, after which each child was assigned to one of the five profiles. The participants then underwent resting-state functional magnetic resonance imaging (fMRI). This method tracks blood oxygen levels and makes it possible to see which brain areas activate synchronously, that is, how they are connected to each other. The researchers divided the brain into 200 cortical and 32 subcortical regions and, using a mathematical framework - graph theory - assessed how strongly these regions are connected to each other and how efficiently they transmit information. Graph theory here is a way of describing a network of connections as a set of numerical indicators.
The data obtained were fed into a machine learning algorithm that looked for patterns between brain connectivity and sensory profile. The algorithm was able to distinguish seven of the ten possible pairs of profiles. It performed best with the two extreme groups - adaptive and generalized sensory differences.
Children in the adaptive group had stronger global connectivity in the prefrontal cortex (responsible for decision-making and planning) and in the orbitofrontal cortex (which helps link sensations with emotions). Children with generalized differences, by contrast, had strengthened local connectivity within the somatomotor network, which processes touch and movement, but weakened connectivity of these areas with the prefrontal cortex. In the group with sensitivity to taste and smell, nodes in the posterior parietal cortex (involved in spatial thinking and attention) worked differently. Subcortical structures such as the thalamus and nucleus accumbens also helped distinguish some profiles.
The authors caution that this is a correlation, that is, a statistical association that by itself does not prove that features of brain connectivity cause sensory differences. In addition, for three pairs of profiles the algorithm did not produce statistically significant differences. The sensory behavior data relied on caregiver reports, which introduces subjectivity. The analysis did not include autism symptom severity, intelligence level or co-occurring conditions. Finally, head movements during scanning could have distorted the measurements, although the researchers discarded some data and applied corrections. Further testing in other groups will show how universal these patterns are.