Coordinated electrical activity in the olfactory bulb gates the oscillatory entrainment of entorhinal networks in neonatal mice
Fig 2
Continuous and discontinuous patterns of oscillatory activity in the neonatal OB.
(A) Digital photomontage reconstructing the track of the DiI-labeled multisite recording electrode (red) in a Nissl-stained (green) 100 μm–thick coronal section including the OB from a P9 mouse. The dots (gray) show the position of the 16 recording sites of the silicon probe and the recording channels (white) in the MCL and EPL that were used for spike and LFP analysis, respectively. (B) LFP recording of the oscillatory activity in the OB of a P10 mouse displayed band-pass filtered in different frequency bands and accompanied by the wavelet spectrogram (white line represents time-averaged power of the trace; white arrows point toward peak frequency values) as well as simultaneously recorded MUA (high-pass filter >400 Hz) and respiration. (C) Characteristic slow continuous oscillatory activity and theta bursts from the trace shown in B when displayed at higher magnification. Insets, continuous oscillatory activity in relationship with respiration (left, blue) and a discontinuous theta burst (right, red). (D) Power spectra (mean ± SEM) of LFP in OB during nonburst activity (blue) and discontinuous bursts (red) as well as of theta bursts normalized to nonbursting activity (purple). The respiration frequency was depicted as a horizontal bar and expanded at larger scale (top). (E) Temporal relationship between neuronal firing and network oscillations in OB. Left, histogram showing the percentage of spikes occurring during theta burst for all clustered units. Right, box plot depicting the firing rates of OB units during nonburst periods and theta burst periods. Gray dots and lines correspond to individual cells (Wilcoxon signed-rank test, ***p < 0.001). (F) Histograms depicting the phase locking of OB cells to RR (left) and theta activity (right). Only significantly locked cells were used for analysis. Data are available in S1 Data. EPL, external plexiform layer; LFP, local field potential; MCL, mitral cell layer; MTC, mitral and tufted cell; MUA, multiunit activity; OB, olfactory bulb; P, postnatal day; RR, respiration-related rhythm.