Many studies have focused on the sensory processing symptoms of autism spectrum disorder (ASD), but relatively few have investigated how people with ASD experience pain. In one of the first studies to research the experience of pain in ASD, researchers from Vanderbilt University found that people with ASD have abnormal neurological responses to pain. The findings could help families and healthcare practitioners understand how people with ASD perceive pain.
The researchers observed the brain activity of 17 adults with ASD and 16 adults without ASD using magnetic resonance imaging (MRI). The participants laid in an MRI scanner with a piece of metal attached to one calf. Over three seconds, the metal heated to 120 degrees Fahrenheit, which is hot enough to hurt, but not hot enough to burn. The metal remained hot for 12 seconds before cooling to room temperature. Participants went through 12 cycles of pain and relief, during which the researchers measured activity in pain-related brain regions. The researchers asked participants to rate their pain on a 10-point scale after the MRI was complete.
The brain goes through three phases in response to pain: early, intermediate, and late. Participants with ASD and participants in the control group demonstrated similar brain activity in pain-related brain regions, like the somatosensory cortex, during the early phase (the warm up and the first seven seconds of heat). In the intermediate and late phases, the control group continued to exhibit brain activity in these regions. However, the participants with ASD showed no activation in the brain’s pain network during these phases. This difference in brain activity persisted for 10 seconds after the painful stimulus stopped. Despite this difference in activity, people with ASD and the control group rated their pain similarly—for most, a seven or eight.
These findings indicate that people with ASD may struggle to process pain and communicate its severity to others. “They’re rating their pain exactly the same, even though their brains respond totally differently. Our study suggests brain imaging might help us clarify pain in individuals who have difficulty communicating their experience verbally,” explains Michelle Failla, the postdoctoral researcher who presented the findings. “If we could combine brain imaging with other ways of determining pain experience, like facial expressions, we might be able to provide even more clarification.”
This research was presented at the 2015 Society for Neuroscience annual meeting.
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