Figure 1.

Rhythmic medial septum-diagonal band of Broca (MS-DbB) neurons and theta (θ): in vivo recordings. (A1) Intracellular recordings of a bursting neuron with large spontaneous θ-like membrane potential oscillations (lower) in the absence of θ in the hippocampal EEG (upper). (A2) As (A1), but irregular bursting and θ. (A3) Change to higher amplitude θ and higher frequency rhythmic bursting induced by sensory stimulation (gentle stroking the animal’s back; red horizontal bar). (A4) Expanded version of part of (A3); (blue square). (B upper) Cross-correlation function (triggered by θ zero crossings, interrupted red line) of hippocampal EEG. (B lower) Cross-correlation histogram of rhythmic busting medial septum (MS) neuron activity showing strong phase locking between both activities. Note the phase advance of the neuron with θ. (C) Reset of hippocampal θ (upper) and of rhythmic bursting MS neuron (lower) triggered by reticular formation stimulation (red arrow); notice the increased amplitude of reset θ. (D) Raster plot showing successive epochs of rhythmic bursting hippocampal interneuron before, during, and after theta burst electrical stimulation of the MS. (E) Cross-correlation histogram showing entrainment by stimulation followed by phase reset (interrupted red lines). Modified from: (A) Barrenechea et al. (1995); (B,C) Gaztelu and Buño (1982); (D,E) Mamad et al. (2015).