The membrane potential of cortical pyramidal cells is constantly being adjusted by the average level of synaptic and action potential activity occurring in the neuron. This hyperpolarization and depolarization of the cell results in marked changes in neuronal responsiveness and accounts for a major part of contrast adaptation and also changes the receptive field strength, and sometimes, size. Thus, the receptive field properties of cortical neurons are dynamically modified through intrinsic as well as network properties. We propose that through these alterations, cortical networks are better able to efficiently encode information.