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Two distinct olfactory bulb sublaminar networks involved in gamma and beta oscillation generation: a CSD study in the anesthetized rat.

Fourcaud-Trocmé N, Courtiol E, Buonviso N - Front Neural Circuits (2014)

Bottom Line: In contrast, the generation of beta oscillation involves the lower part of the EPL and deep granule cells.This differential involvement of sublaminar networks is neither dependent on odor quality nor on the precise frequency of the fast oscillation under study.Overall, this study demonstrates a functional sublaminar organization of the rat OB, which is supported by previous anatomical findings.

View Article: PubMed Central - PubMed

Affiliation: Team Olfaction from Coding to Memory, Center for Research in Neuroscience of Lyon, CNRS UMR5292 - INSERM U1028 Lyon, France ; Team Olfaction from Coding to Memory, Center for Research in Neuroscience of Lyon, Université Claude Bernard Lyon 1 Lyon, France.

ABSTRACT
A prominent feature of olfactory bulb (OB) dynamics is the expression of characteristic local field potential (LFP) rhythms, including a slow respiration-related rhythm and two fast alternating oscillatory rhythms, beta (15-30 Hz) and gamma (40-90 Hz). All of these rhythms are implicated in olfactory coding. Fast oscillatory rhythms are known to involve the mitral-granule cell loop. Although the underlying mechanisms of gamma oscillation have been studied, the origin of beta oscillation remains poorly understood. Whether these two different rhythms share the same underlying mechanism is unknown. This study uses a quantitative and detailed current-source density (CSD) analysis combined with multi-unit activity (MUA) recordings to shed light on this question in freely breathing anesthetized rats. In particular, we show that gamma oscillation generation involves mainly the upper half of the external plexiform layer (EPL) and superficial areas of granule cell layer (GRL). In contrast, the generation of beta oscillation involves the lower part of the EPL and deep granule cells. This differential involvement of sublaminar networks is neither dependent on odor quality nor on the precise frequency of the fast oscillation under study. Overall, this study demonstrates a functional sublaminar organization of the rat OB, which is supported by previous anatomical findings.

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Related in: MedlinePlus

Determination of the mitral cell layer and multielectrode recording examples. (A) Typical recordings at 14 locations along the silicon probe during electrical LOT stimulation. The electrode closest to the signal inversion is numbered 0, which is consequently designated as the closest to the MCL. The EPL and GL are above, and the GRL is below. (B) Typical 15 s recording displayed together with the respiratory signal. Odor presentation is indicated by the black bar. During the SPONT period, there was a slow and large amplitude LFP oscillatory rhythm that reversed at the MCL. During the ODOR period, the slow oscillation reversed close to the GL. (C) Example of an LFP trace showing the alternation of gamma (γ) and beta (β) oscillations on top of the slow rhythm (linked to respiration) at the beginning of the ODOR period (dashed line).
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Figure 1: Determination of the mitral cell layer and multielectrode recording examples. (A) Typical recordings at 14 locations along the silicon probe during electrical LOT stimulation. The electrode closest to the signal inversion is numbered 0, which is consequently designated as the closest to the MCL. The EPL and GL are above, and the GRL is below. (B) Typical 15 s recording displayed together with the respiratory signal. Odor presentation is indicated by the black bar. During the SPONT period, there was a slow and large amplitude LFP oscillatory rhythm that reversed at the MCL. During the ODOR period, the slow oscillation reversed close to the GL. (C) Example of an LFP trace showing the alternation of gamma (γ) and beta (β) oscillations on top of the slow rhythm (linked to respiration) at the beginning of the ODOR period (dashed line).

Mentions: Male Wistar rats (150–350 g) obtained from Charles River Laboratories (L’Arbresle, France) were anesthetized with urethane (i.p. 1.5 mg/kg, with additional supplements as needed) and placed in a stereotaxic apparatus. All experiments were performed in accordance with the guidelines of the European Communities Council. The dorsal region of the OB was exposed. Bulbar activity was recorded as a broadband signal (0.1–5 kHz) using linear 16-channel silicon probes (NeuroNexus Technologies, Ann Arbor, MI) with a homemade, 16-channel DC amplifier. Electrodes on the probe were 50 μm apart (or 100 μm, in the sole case of Figure 1C). The data were digitally sampled at 10 kHz and acquired on a PC using the IOTech acquisition system (Wavebook, IOTech Inc., Cleveland, OH). The respiration signal was recorded using a homemade flow-meter based on a fast response time thermo-dilution airflow sensor. Odors were delivered through a dilution olfactometer (440 ml/min). The recording protocol was as follows: 5 s of spontaneous activity (SPONT), 5 s of odor-evoked activity (ODOR), and 5 s of post-stimulus activity. The odors used were heptanol (A07), ethyl-heptanoate (E07), 2-heptanone (K07), isoamyl-acetate (ISO), and heptanal (D07), each at 10% of the saturated vapor pressure. The time delay between each odor presentation was at least 1 min.


Two distinct olfactory bulb sublaminar networks involved in gamma and beta oscillation generation: a CSD study in the anesthetized rat.

Fourcaud-Trocmé N, Courtiol E, Buonviso N - Front Neural Circuits (2014)

Determination of the mitral cell layer and multielectrode recording examples. (A) Typical recordings at 14 locations along the silicon probe during electrical LOT stimulation. The electrode closest to the signal inversion is numbered 0, which is consequently designated as the closest to the MCL. The EPL and GL are above, and the GRL is below. (B) Typical 15 s recording displayed together with the respiratory signal. Odor presentation is indicated by the black bar. During the SPONT period, there was a slow and large amplitude LFP oscillatory rhythm that reversed at the MCL. During the ODOR period, the slow oscillation reversed close to the GL. (C) Example of an LFP trace showing the alternation of gamma (γ) and beta (β) oscillations on top of the slow rhythm (linked to respiration) at the beginning of the ODOR period (dashed line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4115636&req=5

Figure 1: Determination of the mitral cell layer and multielectrode recording examples. (A) Typical recordings at 14 locations along the silicon probe during electrical LOT stimulation. The electrode closest to the signal inversion is numbered 0, which is consequently designated as the closest to the MCL. The EPL and GL are above, and the GRL is below. (B) Typical 15 s recording displayed together with the respiratory signal. Odor presentation is indicated by the black bar. During the SPONT period, there was a slow and large amplitude LFP oscillatory rhythm that reversed at the MCL. During the ODOR period, the slow oscillation reversed close to the GL. (C) Example of an LFP trace showing the alternation of gamma (γ) and beta (β) oscillations on top of the slow rhythm (linked to respiration) at the beginning of the ODOR period (dashed line).
Mentions: Male Wistar rats (150–350 g) obtained from Charles River Laboratories (L’Arbresle, France) were anesthetized with urethane (i.p. 1.5 mg/kg, with additional supplements as needed) and placed in a stereotaxic apparatus. All experiments were performed in accordance with the guidelines of the European Communities Council. The dorsal region of the OB was exposed. Bulbar activity was recorded as a broadband signal (0.1–5 kHz) using linear 16-channel silicon probes (NeuroNexus Technologies, Ann Arbor, MI) with a homemade, 16-channel DC amplifier. Electrodes on the probe were 50 μm apart (or 100 μm, in the sole case of Figure 1C). The data were digitally sampled at 10 kHz and acquired on a PC using the IOTech acquisition system (Wavebook, IOTech Inc., Cleveland, OH). The respiration signal was recorded using a homemade flow-meter based on a fast response time thermo-dilution airflow sensor. Odors were delivered through a dilution olfactometer (440 ml/min). The recording protocol was as follows: 5 s of spontaneous activity (SPONT), 5 s of odor-evoked activity (ODOR), and 5 s of post-stimulus activity. The odors used were heptanol (A07), ethyl-heptanoate (E07), 2-heptanone (K07), isoamyl-acetate (ISO), and heptanal (D07), each at 10% of the saturated vapor pressure. The time delay between each odor presentation was at least 1 min.

Bottom Line: In contrast, the generation of beta oscillation involves the lower part of the EPL and deep granule cells.This differential involvement of sublaminar networks is neither dependent on odor quality nor on the precise frequency of the fast oscillation under study.Overall, this study demonstrates a functional sublaminar organization of the rat OB, which is supported by previous anatomical findings.

View Article: PubMed Central - PubMed

Affiliation: Team Olfaction from Coding to Memory, Center for Research in Neuroscience of Lyon, CNRS UMR5292 - INSERM U1028 Lyon, France ; Team Olfaction from Coding to Memory, Center for Research in Neuroscience of Lyon, Université Claude Bernard Lyon 1 Lyon, France.

ABSTRACT
A prominent feature of olfactory bulb (OB) dynamics is the expression of characteristic local field potential (LFP) rhythms, including a slow respiration-related rhythm and two fast alternating oscillatory rhythms, beta (15-30 Hz) and gamma (40-90 Hz). All of these rhythms are implicated in olfactory coding. Fast oscillatory rhythms are known to involve the mitral-granule cell loop. Although the underlying mechanisms of gamma oscillation have been studied, the origin of beta oscillation remains poorly understood. Whether these two different rhythms share the same underlying mechanism is unknown. This study uses a quantitative and detailed current-source density (CSD) analysis combined with multi-unit activity (MUA) recordings to shed light on this question in freely breathing anesthetized rats. In particular, we show that gamma oscillation generation involves mainly the upper half of the external plexiform layer (EPL) and superficial areas of granule cell layer (GRL). In contrast, the generation of beta oscillation involves the lower part of the EPL and deep granule cells. This differential involvement of sublaminar networks is neither dependent on odor quality nor on the precise frequency of the fast oscillation under study. Overall, this study demonstrates a functional sublaminar organization of the rat OB, which is supported by previous anatomical findings.

Show MeSH
Related in: MedlinePlus