Odor vapor pressure and quality modulate local field potential oscillatory patterns in the olfactory bulb of the anesthetized rat

Abstract

A central question in chemical senses is the way that odorant molecules are represented in the brain. To date, many studies, when taken together, suggest that structural features of the molecules are represented through a spatio-temporal pattern of activation in the olfactory bulb (OB), in both glomerular and mitral cell layers. Mitral/tufted cells interact with a large population of inhibitory interneurons resulting in a temporal patterning of bulbar local field potential (LFP) activity. We investigated the possibility that molecular features could determine the temporal pattern of LFP oscillatory activity in the OB. For this purpose, we recorded the LFPs in the OB of urethane-anesthetized, freely breathing rats in response to series of aliphatic odorants varying subtly in carbon-chain length or functional group. In concordance with our previous reports, we found that odors evoked oscillatory activity in the LFP signal in both the beta and gamma frequency bands. Analysis of LFP oscillations revealed that, although molecular features have almost no influence on the intrinsic characteristics of LFP oscillations, they influence the temporal patterning of bulbar oscillations. Alcohol family odors rarely evoke gamma oscillations, whereas ester family odors rather induce oscillatory patterns showing beta/gamma alternation. Moreover, for molecules with the same functional group, the probability of gamma occurrence is correlated to the vapor pressure of the odor. The significance of the relation between odorant features and oscillatory regimes along with their functional relevance are discussed.

Odor- and state-dependent olfactory tubercle local field potential dynamics in awake rats

“…We hypothesized that odor information in the OTs of awake rats is represented by changes in LFP spectral power. This straightforward hypothesis follows suit with known aspects of odorevoked LFP activity in the OB and piriform cortex, with each displaying increases in spectral power during odor inhalation (e.g., Buonviso et al 2003;Cenier et al 2008;Chapuis et al 2009;Freeman and Baird 1987;Kay and Beshel 2010). In addition, this hypothesis agrees with the prominent recruitment of neurons within the OT upon odor presentation (Carlson et al 2013;Payton et al 2012;Rampin et al 2012).…”

“…In addition, this hypothesis agrees with the prominent recruitment of neurons within the OT upon odor presentation (Carlson et al 2013;Payton et al 2012;Rampin et al 2012). Among the spectral bands that have received the most attention in terms of being shaped by odor and odor quality, are beta and gamma (Cenier et al 2008;Lepousez and Lledo 2013;Lowry and Kay 2007;Martin et al 2006Martin et al , 2007. We found that the OT is also characterized by considerable beta-band power and detectable, yet minor, gamma-band power.…”

Beta and gamma oscillatory activities associated with olfactory memory tasks: different rhythms for different functional networks?

“…Interestingly, this range includes TMT, a component of fox feces, and toluene. In urethane anesthetized rats, similar observations were made that the molecular feature of odorants influenced the probability of emergence of beta oscillations (Cenier et al, 2008). Consequently, the reason why some odorants elicited higher beta power could be due to their volatility rather than their innate value.…”

The Way an Odor Is Experienced during Aversive Conditioning Determines the Extent of the Network Recruited during Retrieval: A Multisite Electrophysiological Study in Rats

“…This transformation leads, for each trial, to a time frequency matrix where each point represents the level of energy for a given instant and a given frequency: hot color spots represent transitory oscillations. The method used to quantify changes in the beta (15-40 Hz) frequency band is based on the wavelet ridge extraction previously described by Roux et al (2007) and applied to biological signals by Cenier et al (2008). For each trial, a power threshold (mean ϩ 3 STD) was calculated between 15 and 40 Hz on the baseline period.…”