The computations that underlie behavior are thought to be performed by various neuronal circuits. The exact transformation performed by a given circuit is dependent on how synaptic input to the principle neuron engages the electrical properties of its dendrites. A prominent computation in neuronal circuits is a comparison of internal (predictive, stored or prior) inputs and external (sensory, current or data) inputs by pyramidal neurons throughout the CNS. In most regions the internal and external inputs are segregated onto different dendritic regions that have unique electrical properties (distal dendritic versus perisomatic regions). Strong spatio-temporal correlations between the external and internal inputs produce dendritic Ca plateau potentials that shift the action potential output pattern to a burst firing mode. I will present results from slice recordings as well as from awake behaving animals that examine the cellular and network components as well as the behavioral impact of this input comparison type of computation in both the CA1 hippocampus and barrel cortex.