A new article (published in New Journal of Physics), called “The Tongue as an Excitable Medium”, posits an explanation for a condition known as “geographic tongue” by treating the tongue as an excitable medium and conducting a mathematical analysis of pattern formation on it.
Here is the abstract:
Geographic tongue (GT) is a medical condition affecting approximately 2% of the population, whereby the papillae covering the upper part of the tongue are lost due to a slowly expanding inflammation. The resultant dynamical appearance of the tongue has striking similarities with well known out-of-equilibrium phenomena observed in excitable media, such as forest fires, cardiac dynamics, chemically driven reaction-diffusion systems and morphogenesis in multicellular organisms. Here we identify GT as a novel example of excitable media dynamics and explore the evolution of the condition from a dynamical systems perspective. We focus on two characteristic aspects of GT in particular: anisotropic expansion of lesions and re-entry of the inflammation into recovering regions. Our investigation sheds light on the evolution of the inflammation and suggests a practical way to classify the severity of the condition, based on the characteristic patterns observed in GT patients.
I have to compliment the authors on their choice of title, because I bet that pattern formation and the theory of dynamical systems are not what you were thinking when you saw the title of this entry. One of the authors, Gabriel Seiden of the Weizmann Institute of Science, has written about his paper in IFLS. (The picture I have used, which was also used in the IFLS, includes a pattern that is rather canonical of excitable media, though not all geographic tongues have a pattern that is this clearly reminiscent of such systems.)