Hippocampal neurons are extraordinarily interesting to observe in action. As animals perform a variety of natural or learned behaviors, hippocampal principal cells of areas CA1 and CA3, which otherwise are characterized by very low baseline firing rates, suddenly fire at rapid rates related to the current location of the animal, its ongoing behavior, specific salient stimuli, or some combination of these factors and the context of the behavioral situation. Unlike in many brain areas where specific sensory or behavioral correlates of neuronal activity are difficult to observe, in the hippocampus it sometimes seems there are as many behavioral correlates as experimental paradigms in which they might be observed. The challenge is not to find correlates of neural activity in the hippocampus – it is to make sense of the broad range of sensory- and behavior-related firing properties observed.