The cerebral cortex is the largest part of the mammalian brain and plays roles in most flexible behaviors. Discovering the principles that organize cortical circuits and how they process information and guide behavior are major frontiers in brain research. We focus on the neural circuits that underlie whisker-dependent somatosensation. Mice and other rodents use their whiskers to recognize and localize objects. Quantitative behavioral methods allow us to infer algorithms mice might use for object localization. During behavior we record from and manipulate specific neuronal populations to discover relationships between neural activity and behavior. I will present data on how neurons in the somatosensory and motor cortex code for object location. I will also highlight light-based tools, which are playing an increasingly prominent role in recording and manipulating activity in mapped neural circuits.