The olfactory bulb is a source of high-frequency oscillations (130–180？Hz) associated with a subanesthetic dose of ketamine in rodents

Ketamine-enhanced HFO in the OB precedes the VS. a LFP spectrograms of simultaneous recordings in the OB and VS showing the effect of intraperitoneal injection of 25？mg/kg ketamine. Note the strong power of HFO (close to 150？Hz) immediately after injection of ketamine. The same scale is used for both plots. b Time-course showing mean？±？SEM HFO power in the OB (white circles) and VS (black triangles) before and after injection of ketamine (n？=？9 rats). The power of HFO was significantly larger in the OB. c Correlation of HFO power in the OB and VS was highly significant for all rats (each data point represents an individual rat). The mean？±？SEM is also shown. d Ketamine injection was associated with an increase in the mean coherence between the OB and VS, which was prominent at the HFO band. e 130–180？Hz band-pass filtered signal (top pair) and the raw LFP (bottom pair) recorded simultaneously from the OB and VS shortly after injection of ketamine. Bursts of HFO are clearly visible in recordings from both sites. f Expansion of a single HFO burst showing that HFO recorded in the OB precedes the VS. Dotted lines indicate the troughs of HFO in the OB. g Mean waveform correlation for the 130–180？Hz band-pass filtered signal in the VS relative to the OB. Zero is the peak of the OB HFO waveform showing HFO occurs relatively later in the VS. h, i Mean Granger causality relationship for the OB？→？VS and VS？→？OB direction, respectively. j Mean difference between the Granger analyses the contoured areas indicate significant difference