The Nobel prize in Physiology or Medicine has been awarded to John O'Keefe, and the couple May-Britt Moser and Edvard Moser. Below is some description given in the New York times. What does it have to do with multivariable calculus. Actually a lot. The mathematics of calculus on discrete networks is not much different than the calculus of Newton and Leibnitz. More related is actually the nitty-gritty work to get to the spacial data in the brain using inverse computations. These tomography methods rely on integration.

New York Times:

The three scientists' discoveries "have solved a problem that has occupied philosophers and scientists for centuries - how does the brain create a map of the space surrounding us and how can we navigate our way through a complex environment?" said the Karolinska Institute in Sweden, which chooses the laureates. The positioning system they discovered helps us know where we are, find our way from place to place and store the information for the next time, said Goran K. Hansson, secretary of the Karolinska's Nobel Committee. The researchers documented that certain cells are responsible for the higher cognitive function that steers the navigational system. (...) So many large and small questions remain unanswered. How is information encoded and transferred from cell to cell or from network to network of cells? Science found a genetic code but there is no brain-wide neural code; no electrical or chemical alphabet exists that can be recombined to say "red" or "fear" or "wink" or "run." And no one knows whether information is encoded differently in various parts of the brain. (...) The question now on his mind, and that of many neuroscientists, is how larger groups, thousands of neurons, work together - whether to produce an action, like reaching for a cup, or to perceive something, like a flower. There are ways to record the electrical activity of neurons in a brain, and those methods are improving fast. But, he said, "If I give you a picture of a thousand neurons firing, it's not going to tell you anything." Computer analysis helps to reduce and simplify such a picture but, he says, the goal is to discover the physiological mechanism in the data.