Touching something with a hand triggers more than 12,500 tactile nerve fibers, informing a subject about the physical object in contact (texture, temperature, shape, size, motion across the skin, etc.). For years researchers have known how a single tactile fiber encodes tactile information. However, they do not know how the information retrieved by the populations of fibers is encoded.
To help understand this important gap, a team of neuroscientists at the University of Chicago Medical Center have developed a computer model to simulate the responses of all the tactile fibers of the whole hand when subjected to any stimulus applied to the skin. The team of researchers is led by Sliman Bensmaia, associate professor of organismal biology and anatomy at the University of Chicago, and principal investigator for the new research. The tool they developed simulates the responses of more than 12,500 nerve fibers with millisecond precision by first reconstructing the physical stresses experienced by mechanoreceptors when the skin is deformed, and then simulating the response produced in the nerve fiber by the receptor.
This model will allow the scientific community to understand how the population of nerve fibers responds to touch in order to build realistic sensations into bionic hands for amputees. "Almost everything we know about how the nerve responds to stimulation on the skin of the hand is built into this model," said professor Bensmaia. "Finally, you can see how all these nerve fibers work together to give rise to touch."
This development is significant because previous attempts to study this problem included costly and time-consuming experiments with animals and human subjects. Even then no researcher was able to record responses from more than one nerve at a time. In addition to the clear benefit of understanding how these skin sensations work, this computer model will serve as the foundation for restoring touch in bionic hands.
Professor Bensmaia and his team validated the model by comparing data collected by other research teams, and showed that the computer model matches the other researcher’s output with millisecond precision. "Using a model to reproduce a biological system precisely is challenging, and we have been working on this simulation for a very long time. But the final product, I think, is worth it," Bensmaia said. "It's a tool that will yield insights that were previously unattainable."
The deployment of the software will be open-source and made available as a free download.
The results of the research and the details of the model were published June 27 in the Proceedings of the National Academy of Sciences. An abstract can be found here: http://www.pnas.org/content/early/2017/06/27/1704856114.abstract