Synchronized Activity in The Main and Accessory Olfactory Bulbs and Vomeronasal Amygdala Elicited by Chemical Signals in Freely Behaving Mice

Abstract

Chemosensory processing in mammals involves the olfactory and vomeronasal systems, but how the activity of both circuits is integrated is unknown. In our study, we recorded the electrophysiological activity in the olfactory bulbs and the vomeronasal amygdala in freely behaving mice exploring a battery of neutral and conspecific stimuli. The exploration of stimuli, including a neutral stimulus, induced synchronic activity in the olfactory bulbs characterized by a dominant theta rhythmicity, with specific theta-gamma coupling, distinguishing between vomeronasal and olfactory structures. The correlated activation of the bulbs suggests a coupling between the stimuli internalization in the nasal cavity and the vomeronasal pumping. In the amygdala, male stimuli are preferentially processed in the medial nucleus, whereas female cues induced a differential response in the posteromedial cortical amygdala. Thus, particular theta-gamma patterns in the olfactory network modulates the integration of chemosensory information in the amygdala, allowing the selection of an appropriate behaviour.

Signal Detection and Coding in the Accessory Olfactory System

“…Observation of species that exhibit an overt Flehmen response, often regarded as an indicator of vomeronasal sampling, indicates that vomeronasal uptake is associated with processing of socially relevant stimuli ( Houpt et al 1989 ; Stahlbaum and Houpt 1989 ; Sankar and Archunan 2004 ). Consistent with this, single unit ( Luo et al 2003 ) and local field potentials recordings from the AOB ( Tendler and Wagner 2015 ; Pardo-Bellver et al 2017 ) of behaving rodents provide real-time evidence that social investigation is indeed associated with AOS activation. Thus, although it is well established that vomeronasal function is associated with social investigation (and likely with risk assessment behaviors), a good understanding of AOS stimulus uptake dynamics is still missing.…”

“…Another related aspect concerns the role of local field potentials. Several in vivo studies in behaving animals have shown signatures of local field potential fluctuations, in bands similar to those observed in the MOS, during stimulus processing ( Binns and Brennan 2005 ; Leszkowicz et al 2012 ; Tendler and Wagner 2015 ; Pardo-Bellver et al 2017 ). Specific remaining questions include the following: How are these oscillations generated?…”

Olfaction and Pheromones: Uncanonical Sensory Influences and Bulbar Interactions

“…While integrated responses motivated by odorant and/or pheromonal stimuli are customarily attributed to axonal convergence beyond the olfactory bulb (see Mohedano-Moriano et al, 2012 ; Keshavarzi et al, 2015 ), recent evidences support the existence of an intra-bulbar network (Figure 1 ; Pardo-Bellver et al, 2017 ). A direct link between the dMOB and AOB was first suspected by experimental lesioning of the former, leading to orthograde degeneration in the latter (Larriva-Sahd, 2008 ); then, reciprocal interactions between them have been characterized (Vargas-Barroso et al, 2016 ; see Martinez-Garcia et al, 1991 ).…”

Wavelet Correlation Analysis for Quantifying Similarities and Real-Time Estimates of Information Encoded or Decoded in Single-Trial Oscillatory Brain Waves

“…in different olfactory regions [8]. In the third study, the Hilbert transform was used to identify the dominant oscillations of the odor-evoked responses in the theta band in the posterior piriform cortex with phase-locked activities in the hippocampus in humans [9].…”

“…Regarding mental states, the most important individual-independent frequencies of electroencephalography (EEG) are 7-12 Hz at the P1 electrode and <5 Hz at Fz for attention, 10-20 Hz at F4 for fatigue, and 4-7 Hz at Fz and 10-20 Hz at Cz for frustration, with even greater variations in frequencies observed across individuals [2]. Alpha-band oscillations (8)(9)(10)(11)(12)(13) Hz) exert top-down influences on the early visual processing for attention orienting [3] and are sensitive markers in the auditory memory loading process [4]. As a test case, we applied a wavelet correlation analysis to estimate odor information in the fine temporal structures of single-trial brain waves.…”