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Decreased Neural Response to Touch As a Marker of Autism Risk Across the First Year of Life
Touch is an important means of social communication between parents and infants and facilitates social interactions throughout the lifespan. Neuroimaging studies have revealed that slow (affective) touch selectively activates areas of the brain also involved in social perception of visual stimuli (e.g., posterior superior temporal sulcus, medial prefrontal cortex); the level of activation in these areas negatively correlates with levels of autistic traits in typical adults. Additionally, individuals with autism spectrum disorder (ASD) and infants at risk for ASD show diminished responses in these brain regions during visual social perception tasks. It is not clear whether similar deficits are apparent in the neural responses to tactile social perception tasks in infants who are at elevated risk for ASD.
Objectives:
To investigate neural responses to affective (slow) versus non-affective (fast) touch using functional near infrared spectroscopy (fNIRS) in infants at high- and normal-risk for ASD across the first year of life.
Methods:
Participants were 40 infants at high-risk (n=17) or normal-risk (n=23) for ASD. High-risk children had at least one older sibling with ASD, while normal-risk children had no known family history of the disorder. Infants visited the laboratory with their parent at approximately 3 (n=13), 6 (n=9), 9 (n=8) or 12 (n=10) months of age. Prior to the experimental procedures, infants were outfitted with the fNIRS optode headgear and were seated on their parent’s lap. The tactile perception task consisted of 8 periods each of slower (0.5 Hz) and faster-paced (2.5 Hz) brushing to the skin of the infant’s leg, which alternated with periods of no tactile contact. Both oxygenated and deoxygenated hemoglobin responses were recorded with a Hitachi ETG4000 fNIRS transcranial optical topography system.
Results:
Epochs of fNIRS data were extracted from each optode around the stimulus presentation (-1 sec – 7 sec) and averaged by brushing type (fast, slow) for each participant. At optode sites over left superior temporal cortex, high-risk infants, in comparison to normal-risk infants, showed decreased responses to fast brushing 1-5 seconds after the beginning of the stimulation. This response was seen in infants at 3, 6, and 12 months of age. No consistent differences were seen in response to slow brushing across the first year of life.
Conclusions:
This is the first known study to examine neural responses to a tactile social perception task in infants at-risk for ASD across the first year of life. We found that infants at high- and normal-risk of developing ASD have differential sensitivity to tactile stimuli. Our results suggest that (1) areas of the temporal cortex (superior temporal cortex), which is known to respond to visual social cues, also play a role in the processing of tactile social information. (2) Differences in response to tactile stimulation evident in the first year of life are a potential biomarker for elevated risk of ASD.