Figure 7.

Rhythmic stimulation of fornix/fimbria evoked IPSPs, which significantly activated putative GABAergic neurons of the MS/DB. A, Effect of fornix stimulation (stim) on electrophysiologically identified MS/DB neurons. Compared with baseline level (bsl), the firing of fast- and burst-firing neurons was dramatically increased during rhythmically evoked IPSPs, whereas that of slow- and cluster-firing cells was not changed. Error bars represent SEM (***p < 0.001). B, C, Phase-firing pattern of fast- and burst-firing neurons during rhythmic stimulation of the fornix. The phase histograms show that both fast- and burst-firing neurons exhibit maximal discharge probability just before the following stimulation in each cycle consistent with rebound activation. A Gaussian fit is shown for both distribution (solid gray line), and a dashed vertical line marks the point of stimulation (360°).