Variable coupling between olfactory system activity and respiration in ketamine/xylazine anesthetized rats.
ABSTRACT In this study, we have characterized slow and fast oscillations at several stages of olfactory processing under light and deep ketamine/xylazine anesthesia in the albino rat. While monitoring the animal's respiration, we also obtained field potentials from the olfactory bulb and piriform (olfactory) cortex and simultaneously recorded membrane potentials in piriform cortex pyramidal cells. Our results demonstrate that oscillations are generally found at higher frequencies under lighter and lower frequencies under deeper anesthesia. In previous studies of cerebral cortex, similar results in ketamine/xylazine anesthetized animals have been interpreted to correspond with the higher frequencies found during waking and lower frequencies found in the sleep state. Correlation and coherence analysis between data obtained in the bulb and cortex reveals a clear difference in coupling depending on the anesthetic state of the animal. Specifically, activity recorded in the whole system is highly correlated with respiration during deep anesthesia, whereas only the olfactory bulb, and not the cortex, is correlated with respiration during light anesthesia. These data suggest that global activity in the piriform cortex is actually more directly tied to peripheral slow respiratory input during slow wave than fast wave states and that the coupling between olfactory structures can be dynamically modulated by the level of anesthesia and therefore presumably by different brain states as well.
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ABSTRACT: We review data demonstrating that single-neuron sensory responses change with the states of the neural networks (indexed in terms of spectral properties of local field potentials) in which those neurons are embedded. We start with broad network changes--different levels of anesthesia and sleep--and then move to studies demonstrating that the sensory response plasticity associated with attention and experience can also be conceptualized as functions of network state changes. This leads naturally to the recent data that can be interpreted to suggest that even brief experience can change sensory responses via changes in network states and that trial-to-trial variability in sensory responses is a nonrandom function of network fluctuations, as well. We suggest that the CNS may have evolved specifically to deal with stimulus variability and that the coupling with network states may be central to sensory processing.Journal of Neurophysiology 08/2008; 100(3):1160-8. · 3.32 Impact Factor
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ABSTRACT: Different types of oscillations in the olfactory bulb (OB), including θ (1 to 4 and 5 to 12 Hz), β (13 to 30 Hz), and γ oscillations (31 to 64 and 65 to 90 Hz), are important in olfactory information processing and olfactory-related functions and have been investigated extensively in recent decades. The awake and anesthetized states, 2 different brain conditions, are used widely in electrophysiologic studies of OB. Chloral hydrate, pentobarbital, and urethane are commonly used anesthetics in these studies. However, the influence of these anesthetics on the oscillations has not been reported. In the present study, we recorded the local field potential (LFP) in the OB of rats that were freely moving or anesthetized with these agents. Chloral hydrate and pentobarbital had similar effects: they slightly affected the power of θ oscillations; significantly increased the power of β oscillations; significantly decreased the power of γ oscillations, and showed similar recovery of γ oscillations. Urethane had very different effects: it significantly increased oscillations at 1 to 4 Hz but decreased those at 5 to 12 Hz, decreased β and γ oscillations, and showed no overt recovery in γ oscillations. These results provide experimental evidence of different effects of various anesthetics on OB oscillations and suggest that the choice of anesthetic should consider the experimental application.Journal of the American Association for Laboratory Animal Science: JAALAS 01/2012; 51(4):458-63. · 0.71 Impact Factor
Article: Cortical processing of odor objects.[show abstract] [hide abstract]
ABSTRACT: Natural odors, generally composed of many monomolecular components, are analyzed by peripheral receptors into component features and translated into spatiotemporal patterns of neural activity in the olfactory bulb. Here, we will discuss the role of the olfactory cortex in the recognition, separation and completion of those odor-evoked patterns, and how these processes contribute to odor perception. Recent findings regarding the neural architecture, physiology, and plasticity of the olfactory cortex, principally the piriform cortex, will be described in the context of how this paleocortical structure creates odor objects.Neuron 11/2011; 72(4):506-19. · 14.74 Impact Factor