The hippocampal formation is crucial for remembering episodes in one's life, and evidence suggests that synchronous activity throughout the hippocampus is essential for the mnemonic functions of this brain structure. We have studied the mechanisms of synchronization using electrophysiological and computational methods. More recently, we have exploited methods for introducing real-time control in cellular electrophysiology. These techniques allow us to "knock in" virtual ion channels that can be controlled with great mathematical precision, and to immerse biological neurons in real-time, virtual neuronal networks. These manipulations allow us to test computationally-based hypotheses in living cells. From this work, we will discuss which properties of single cells seem crucial for coherent activity in the hippocampal formation, and describe how neuromodulation and apparent pathophysiological changes in channel density lead to changes in network synchronization.