Sniffing behaviour‐related changes in cardiac and cortical activity in rats

Abstract

Key points High‐frequency (HF) sniffing represents active odour sampling and an increase in the animal's motivation. We examined how HF sniffing affects the physiological activity of the brain–body system. During HF sniffing, heart rates and the ratio of theta to delta critical local field potential power were comparable to those observed during motion periods. Vagus nerve spike rates did not vary depending on HF sniffing. Our results suggest that physiological factors in the central nervous system and the periphery are not simply determined by locomotion but are crucially associated with HF sniffing. Abstract Sniffing is a fundamental behaviour for odour sampling, and high‐frequency (HF) sniffing, generally at a sniff frequency of more than 6 Hz, is considered to represent an animal's increased motivation to explore external environments. Here, we examined how HF sniffing is associated with changes in physiological signals from the central and peripheral organs in rats. During HF sniffing while the rats were stationary, heart rates, the magnitude of dorsal neck muscle contraction, and the ratio of theta to delta local field potential power in the motor cortex were comparable to those observed during motion periods and were significantly higher than those observed during resting respiration periods. No pronounced changes in vagus nerve spike rates were detected in relation to HF sniffing. These results demonstrate that central and peripheral physiological factors are crucially associated with the emergence of HF sniffing, especially during quiescent periods. Behavioural data might be improved to more accurately evaluate an animal's internal psychological state if they are combined with a sniffing pattern as a physiological marker.

Theta-Range Oscillations in Stress-Induced Mental Disorders as an Oscillotherapeutic Target

“…In addition to brain electrophysiological recordings, we conceived a recording approach in which a multichannel recording device extends to the collection of bioelectrical signals from peripheral organs, such as electrocardiogram (ECG) signals, electromyogram (EMG) signals ( Okada et al, 2016 ; Okonogi et al, 2018 ; Shikano et al, 2018 ), olfactory bulb respiratory (Resp) signals ( Kuga et al, 2019 ), and vagus nerve (VN) signals ( Shikano et al, 2019 ) ( Figure 1D ), all of which can be captured by a single recording device. This recording method is useful for precisely monitoring signals representing changes in peripheral organ activity related to emotion, stress, and mental disorders, in addition to simple behavioral phenotypes.…”

Enhancement of Motor Cortical Gamma Oscillations and Sniffing Activity by Medial Forebrain Bundle Stimulation Precedes Locomotion

“…3 A , B ). We bandpass-filtered the OB ECoGs at 1–4 Hz, 4–9 Hz, and 30–90 Hz; these frequency bands correspond to low-frequency sniffing, high-frequency sniffing ( Kuga et al, 2019 ), and gamma oscillations, respectively ( Bagur et al, 2018 ). Compared with the baseline, when the MFB was periodically stimulated, we found a significant increase in the power of the OB ECoGs for low-frequency sniffing [2.66 ± 0.94 × 10 3 μV 2 (baseline) vs 1.32 ± 0.56 × 10 4 μV 2 (stim), p = 0.03, t (7) = 2.71, d = 0.96, n = 8 rats, paired t test, p = 0.28, W = 0.90, Shapiro–Wilk test; Fig.…”

“…3 , 5 ). Regarding OB activity, high-frequency sniffing is often observed when animals are motivated to explore an external environment ( Wesson et al, 2008 ; Kuga et al, 2019 ) and may play a role in the acquisition of olfactory information to guide their ongoing behavior ( Kepecs et al, 2006 ; Ranade et al, 2013 ; Kleinfeld et al, 2016 ). Consistent with a previous study on sniffing responses based on thermal changes in the rat nasal cavity ( Waranch and Terman, 1975 ), we observed intense high-frequency sniffing activity immediately after MFB stimulation ( Fig.…”

“…The EIB of the recording interface assembly was connected to a digital headstage (CerePlex M, Blackrock Microsystems), and the digitized signals were amplified and transferred to a data acquisition system (CerePlex Direct, Blackrock Microsystems; Okada et al, 2016 ; Kuga et al, 2019 ). ECoG signals were digitized at a sampling rate of 2 kHz.…”

Slow gamma oscillations in the mouse olfactory bulb are correlated with sniffing in the dark period

“…This nasal breathing pattern is further classified into slower (<4 Hz) and faster (>6 Hz) components that usually indicate respiration and (fast) sniffing, respectively. In particular, (fast) sniffing is involved in active perception that contributes to motivation for exploration and social interactions [11,12]. In contrast, the high-frequency component of LFPs is called gamma oscillations produced in various regions, including the olfactory bulb, hippocampus, and neocortex.…”