Hippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary “pacemaker” timing signal is imposed on the hippocampal system, or it may assist in organizing target subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to test these models. Cooling of the MS reduced both theta frequency and power and was associated with an enhanced incidence of errors in a spatial navigation task, but it did not affect spatial correlates of neurons. MS cooling decreased theta frequency oscillations of place cells and reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. Thus, the septum is critical for sustaining precise theta phase coordination of cell assemblies in the hippocampal system, a mechanism needed for spatial memory.

海马 theta 振荡协调神经元放电以支持记忆和空间导航。内侧中隔 (MS) 通过两种可能的机制在 theta 生成中至关重要：单一的“起搏器”计时信号被施加到海马系统上，或者它可能有助于在 theta 振荡的相空间内组织目标子电路。我们使用 MS 的温度控制来测试这些模型。MS 的冷却降低了 theta 频率和功率，并且与空间导航任务中错误的发生率增加有关，但它不影响神经元的空间相关性。MS 冷却降低了位置单元的 theta 频率振荡并减少了距离-时间压缩，但在 theta 周期内保留了位置场序列的距离-相位压缩。因此，