Autism: A Short Circuit in the Touch System?

when Temple Grandin was growing up, her skin seemed to be crawling beneath her clothes. “Scratchy petticoats felt like sandpaper ripping off my skin,” said Grandin, an autism-rights advocate and animal scientist at Colorado State University. “There is no way a child is going to function in a classroom if his or her underwear feels like it is full of sandpaper.”

Many other individuals with autism are also extremely sensitive to touch, and some of the earliest descriptions of the disorder mention that infants with autism might cry or arch their backs when held.

It’s no longer one of those hippie, ‘give me a cuddle’ things. There are nerve fibers underlying this.

But why? Some researchers suspect that the answer might lurk in a system of nerves known as C-tactile afferents. While the fast, thick nerves beneath our fingertips help us tell the difference between silk and cotton, and the slower, thinner nerves nearby transmit pain, C-tactile (CT) afferents, found under hairy regions of the skin, carry information about social interactions. They respond to slow, gentle strokes — the same soft caress you’d give a baby’s cheek or a lover’s arm.

Last week, Francis McGlone, a cognitive neuroscientist, and his colleagues at Liverpool John Moore University published a commentary in the journal Neuronoutlining current knowledge on CT afferents — including studies suggesting that they might play a role in autism and other developmental disorders. If so, then CT function could be assessed at birth or within days of birth to screen for these disorders, well before behavioral symptoms appear.

Although earlier studies have found that gentle stroking can lower stress and blood pressure levels, the neurobiological mechanisms have remained largely a mystery, until recently. “It’s no longer one of those hippie, ‘give me a cuddle’ things,” McGlone said. “There are nerve fibers underlying this.”

CT afferents were first described in a cat’s leg in 1939, and then in rats and monkeys. In the late 1980s and early ’90s, Swedish scientists Ake Vallbo and Karl-Erik Hagbarth discovered that they also existed in humans after they inserted a tiny electrode into volunteers’ skin to record the electrical activity of the underlying nerves. One group of nerves — the CT afferents — fired only when the skin was gently stroked. …..

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