The study focuses on the central role of the medial septum (MS), a critical component of the basal forebrain nucleus, in supporting various physiological activities such as sensorimotor integration and memory consolidation. The primary goal is to unravel the intricate information transfer mechanism between the MS and the hippocampus during memory formation, with a particular focus on the involvement of MS neurons in both hippocampal theta wave and ripple generation.To achieve this goal, a patch-clamp methodology was used for in vivo recording of MS neuronal activity. This approach was designed to elucidate the membrane potential dynamics of MS neurons during hippocampal ripples, providing new insights into the complex neural mechanisms underlying MS-hippocampal memory formation.Historically, MS research has focused primarily on recording extracellular activity due to the technical challenges associated with using the patch-clamp method to record intracellular membrane potential in deep brain regions, including the MS. A major breakthrough came with the introduction of the tissue-removal method, which allowed global recording of membrane potentials from awake mouse MS neurons for the first time.Subsequent analysis of MS firing rates and membrane potential fluctuations before and after hippocampal ripples, simultaneously recorded by hippocampal local field potentials, revealed that GABAergic neurons tended to hyperpolarize before hippocampal ripples, whereas glutamatergic neurons tended to hyperpolarize after ripples. The temporal disparity in the onset of inhibition suggests potentially different roles for the underlying signal transduction mechanisms and neural circuits in the complex process of memory formation.