Neuroscience research is now conducted at all levels of organization: starting from single neurons and their synaptic connections, to ensembles of neurons working in concert, to brain systems that contain those ensembles, to the behavior of the whole animal during cognitive testing. Our experimental goal is to use an integrative analysis employing a range of techniques that cover the cellular and molecular, neural-ensemble and behavioral levels. Specifically, we use genetically modified mice to obtain specific perturbations of cognitive function. We scrutinize these mice with tests for behavioral performance (a battery of tasks that measure cognition in mice), behavioral physiology (multi-electrode recordings of neuronal ensembles in freely moving mice), and the examination of synaptic plasticity (electrophysiological recordings in hippocampal slices). Finally, we use computational methods to integrate experimental data into quantitative models.