Figure 1.
Identification of recording site locations and laminar specific changes in hippocampal network synchrony during REM sleep versus active waking behavior. (A,B) Anatomical positions of recording sites were localized for each recording session by aligning the histology with several spontaneous and evoked activity patterns (see Methods). (A) Histological sections with DiI labeling of electrode tracks (yellow) overlaid with estimated locations of single units (red points; location estimated from waveform amplitudes; putative cell types: triangle=principal cell, circle=interneuron, diamond=unclassified) and average perforant path evoked potentials (black traces, n=3). Note the EPSP-associated negativity in the dentate molecular layer, and monosynaptic and disynaptic population spikes in the dentate and CA3 respectively resulting from perforant path stimulation. (B) Ripple-triggered average LFP responses (black traces, centered on ripple event, n=179) overlaid on normalized ripple power (color, 120–250Hz) and outline of histological features (gray lines). (C,D) Example of raw local field potential traces recorded during REM sleep and running in a maze. (C) One second LFP traces from CA1 stratum radiatum (CA1sr) and the dentate granule layer (DGgl). (D) LFP activity (0.5 seconds overlapping with trace in C) centered on the anatomical location from which the trace was recorded. Note the higher theta and gamma oscillation amplitudes on dentate recording sites during REM sleep, but the larger gamma in CA1sr during wake. Signals were spatially interpolated over a priori identified defunct recording sites (see methods).