The cerebral cortex is the largest part of the mammalian brain and plays a role in most flexible behaviors. Neocortical circuits are remarkably similar across species, and to some extent also across functional areas. Our goal is to understand the principles that organize neocortical circuits and to decipher how they process information and guide behavior.The research program is mainly organized around the neural circuits that subserve whisker-dependent somatosensation in the mouse. We use a variety of anatomical, optical and electrophysiological methods to map the circuit diagram underlying somatosensation. Quantitative behavioral paradigms in head-fixed mice allow us to use reductionist methods to probe the dynamics of neurons and synapses in awake animals. For example, imaging activity in identified neuronal populations in the circuit can guide the development of hypotheses about the algorithms underlying sensory perception and behavior. These hypotheses can then be tested using gain-of-function and loss-of-function manipulations in genetically targeted neuronal populations. In addition, we have a long-standing (but waning) interest in basic mechanisms of synaptic function and experience-dependent synaptic plasticity. Our current research is focused on what is the logic underlying neocortical structure and function? Answering this question will require precise measurements and perturbations of specific neuronal populations in behaving animals.