A: Nissl-stained 20 μm cryosection of DIV 7 hippocampus slice. B: Evoked activity, arrow shows the stimulus artifact, left: stimulus electrode in DG, recording electrode in CA3, right: stimulus electrode in CA3, recording electrode in CA1. C: spontaneous activity in CA1, D: short and long spontaneous bursts in CA1. Recordings in B-D were carried out with glass electrodes.