A new study has shed light on the complex interactions between the senses of taste and touch, explaining the science behind the tingling sensation caused by eating a popular Asian spice- Szechuan pepper.
The study could lead to a greater understanding of the causes of the tingling sensations experienced by many chronic pain patients.
The researchers University College London found that Szechuan pepper, which is widely used in Asian cooking, mimics the sense of touch in the brain.
It chemically activates light-touch fibres on the lips and tongue and sends the equivalent of 50 light taps to the brain per second.
Lead author of the study, Dr Nobuhiro Hagura, said that this is the first time that researchers have been able to show how chemicals activate touch fibres, inducing a measureable frequency.
While it is well known that natural products like chilli, mustard oil and menthol can activate the thermal and pain fibres in the skin, they wanted to find out why Szechuan pepper specifically works on the light-touch fibres, producing a conscious sensation of touch and that distinctive tingling feeling.
After Szechuan pepper was applied to the lips of volunteers, participants were asked to match the frequency of the resulting tingling sensation by adjusting a vibrating stimulus, either higher or lower, on their fingertips.
The team was able to show that an active ingredient in the peppers stimulates specific RA1 fibres in the lips and tongue.
"What we found was that a unique active ingredient in the pepper, called sanshool, activates these fibres, sending a highly specific signal to the brain. Szechuan peppers and physical touch sensations share this same pathway to the brain," Hagura said.
The study is published in the journal Proceedings of the Royal Society B.
