Coordinated electrical activity in the olfactory bulb gates the oscillatory entrainment of entorhinal networks in neonatal mice
Fig 3
Effects of optogenetic silencing of MTCs on the patterns of oscillatory activity in the neonatal OB.
(A) Photograph of the brain of a P8 cre+ Tbet-cre;ArchT-EGFP mouse (left) showing EGFP-fluorescent MTCs cell bodies and their projections. (B) Left, photograph of a 100 μm–thick coronal section including the OB from a P8 cre+ Tbet-cre;ArchT-EGFP mouse. The position of recording sites in MCL and EPL layers is marked by white squares. The light guide ending just above the recording sites is shown in gray. The iso-contour lines of light spreading calculated using Monte Carlo simulation are shown in yellow. Right, propagation of light intensity in the brain as predicted by Monte Carlo simulation. Yellow lines correspond to the iso-contour lines for light power of 1 and 10 mW/mm2, respectively. (C) Neuronal firing (SUA) and LFP band-pass filtered for different frequency bands (broad 1–100 Hz, RR 2–4 Hz, theta 4–12 Hz) in response to light (yellow, 594 nm) stimulation of MTCs in a P8 cre+ Tbet-cre;ArchT-EGFP mouse. Traces are accompanied by the color-coded wavelet spectrogram of LFP shown at an identical timescale. (D) Raster plots and peristimulus time histograms displaying the firing of MTCs in response to light stimulation. The color-coded bar (bottom) displays the fraction of cells that responded with a firing decrease during stimulus (red), constant firing during stimulus but a firing increase post stimulus (blue), and unchanged firing rate (white). (E) Box plots displaying the absolute power before and during light stimulation in cre+ pups (left) and the relative change of RR activity in neonatal OB of cre+ and cre− mice (right). Gray dots and lines correspond to individual animals. (F) Same as E for discontinuous theta bursts (**p < 0.01, left: signed-rank test, right: rank-sum test). Data are available in S1 Data. EGFP, enhanced green fluorescent protein; EPL, external plexiform layer; LFP, local field potential; MCL, mitral cell layer; MTC, mitral and tufted cell; OB, olfactory bulb; P, postnatal day; RR, respiration-related rhythm; SUA, single-unit activity.