Math and biology meet in the cerebellum.

The ability to perceive your surroundings depends on rapid eye movements, known as saccades, that direct your gaze to objects, people, landmarks, and so forth. When all goes well, each saccade moves your eyes exactly to your intended target. This accuracy relies on constant finetuning by neurons within the cerebellum, which contains roughly half of the neurons in the human brain. Because saccades are fast and must move in a precise direction, fine-tuning must be precise in time and direction. A paradox is that the output neurons of the cerebellar cortex, Purkinje cells, have activity that is neither temporally nor spatially precise. How can seemingly imprecise responses fine-tune saccades? On page 869 of this issue, Fakharian et al. (1) report how they address this paradox. In doing so, their study grounds seemingly abstract mathematical concepts in the detailed biology of this remarkable brain area. [ABSTRACT FROM AUTHOR]