How do sensory signals in different parts of the brain get combined to form a single unified perception that we experience? Despite amassing a wealth of detail in the past century about the cellular components of the brain, this fundamental question as to how their activities are coordinated or integrated, remains largely unanswered. The experiments proposed here would begin to uncover how neurons in the rat's touch sensory system combine signals from long whiskers on the two sides of its face when it judges the width of a tunnel opening in the dark. The approach is to record the electrical activity of sensory neurons while trained rats report whether they sense a wide or a narrow opening with their facial whiskers. Selectively turning off neurons on one side of the brain or the other (using a drug) will quantify how much the signals from the two sides of the face are being mixed in different task conditions. Thus these experiments will begin to explain the remarkable ability of neurons to change the mix of sensory inputs in order to adapt and optimize their processing for changing circumstances. Using the rat as a model system makes it feasible to probe fundamental cellular mechanisms by which assemblies of neurons communicate. Principles of flexible neural communication gleaned from the rat model will likely shed light on analogous neural organization in evolutionarily higher organisms including humans. At the same time, the next generation of undergraduate women will be trained in quantitative analysis and cutting-edge behavioral neurophysiology techniques.