Olfaction in rats with extensive lesions of the olfactory bulbs: implications for odor coding

Lu, Xuenong; Slotnick, Burton M.

doi:10.1016/s0306-4522(97)00520-4

Cited by 100 publications

(76 citation statements)

References 52 publications

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“…Therefore, the implanted cannulae, puncture of the main olfactory bulbs by the injection needle, and the bilateral 2-µL saline injection had no detectable impact on the behavior. This was consistent with the studies of Slotnick and coworkers showing that only major lesions encompassing Ն80% of the MOB led to deficits in odor discrimination (Lu and Slotnick 1998).…”

Section: Resultssupporting

confidence: 93%

Adrenergic modulation of olfactory bulb circuitry affects odor discrimination

Doucette¹,

Milder²,

Restrepo³

2007

Learn. Mem.

133

132

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A rodent's survival depends upon its ability to perceive odor cues necessary to guide mate selection, sexual behavior, foraging, territorial formation, and predator avoidance. Arguably, the need to discriminate odor cues in a complex olfactory environment requires a highly adaptable olfactory system. Indeed, it has been proposed that context-dependent modulation of the initial sensory relay could alter olfactory perception. Interestingly, 40% of the adrenergic innervation from the locus coeruleus, fibers that are activated by contextual cues, innervates the first relay station in the olfactory system (the main olfactory bulb). Here we utilize restricted pharmacological inhibition of olfactory bulb noradrenergic receptors in awake-behaving animals. We show that combined blockade of ␣ and ␤ adrenergic receptors does not impair two-odor discrimination behavior per se but does impair the ability to discriminate perceptually similar odors. Thus, contextual cues conveyed by noradrenergic fibers alter processing before the second synapse in the olfactory cortex, resulting in tuning of the ability to discriminate between similar odors.Particularly intriguing, but poorly understood, is the potential role of adrenergic modulation of the main olfactory bulb (MOB) in adults. The MOB receives strong innervation from the locus coeruleus (LC)-noradrenaline (NA) system, and in rodents ∼40% of LC fibers target the MOB. The fibers are known to be densest in the internal plexiform and granule cell layers, less dense in the external plexiform layer, and sparse in the glomerular layer (McLean et al. 1989) (Fig. 1). Both ␣ and ␤ adrenergic receptors are expressed by cells in the MOB (Pieribone et al. 1994;Woo and Leon 1995;Day et al. 1997). Current evidence suggests that the LC-NA system has a behaviorally meaningful role within the MOB of adult animals engaged in olfactory learning tasks. There is a modest but reproducible release of NA in the MOB during operant conditioning in adult mice (Brennan et al. 1998). In addition, detection of the rewarded odor, presumably relayed from the prefrontal cortex to LC, triggers a brief phasic increase in firing of LC neurons (Bouret and Sara 2004). Gray and coworkers also find that the topical application of propranolol, a ␤ adrenergic antagonist, to the MOB abolished changes in ␥ frequency (40-100 Hz) oscillations in the local field potential elicited by the rewarded odor in an odor discrimination task (Gray et al. 1986). The modulation of odor-induced local field potential oscillations has been postulated to play a role in olfactory learning (Martin et al. 2006). Surprisingly, although the adrenergic effect on odor-induced changes in local field potential oscillations found by Gray and coworkers was robust, propranolol did not change the ability of rabbits to discriminate between odors. Data presented in this paper provide an explanation for the paradoxical observation of Gray and coworkers, as we show that blockade of both ␣ and ␤ adrenergic receptors in the MOB is necessary to attain a chan...

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Section: Resultssupporting

confidence: 93%

Adrenergic modulation of olfactory bulb circuitry affects odor discrimination

Doucette¹,

Milder²,

Restrepo³

2007

Learn. Mem.

133

132

View full text Add to dashboard Cite

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“…In general, the present results are in agreement with our previous studies showing that surgical disruption of identified patterns of bulbar inputs are primarily without effect in a variety of behavior tests, including those for odor quality (Lu and Slotnick, 1994;Slotnick and Bodyak, 2002;Bisulco and Slotnick, 2003), sensitivity (Slotnick et al, 1997), and two-odor and odor mixture discrimination tasks (Slotnick et al, 1989;Lu and Slotnick, 1998;Bisulco and Slotnick, 2003). One explanation for these outcomes is that extensive training may have altered patterns of bulbar activation.…”

Section: Discussionsupporting

confidence: 93%

Discrimination between the Enantiomers of Carvone and of Terpinen-4-ol Odorants in Normal Rats and Those with Lesions of the Olfactory Bulbs

McBride¹,

Slotnick²

2006

J. Neurosci.

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We assessed (1) whether the enantiomers of terpinen-4-ol, odorants that activate nearly identical areas of the olfactory bulb, are more difficult to discriminate than those of carvone, odorants that activate different areas of the olfactory bulb, and (2) whether olfactory bulb lesions that disrupt the pattern of bulbar activation produced by these enantiomers degraded the ability of rats to discriminate between them. In psychophysical tests, normal rats discriminated between the enantiomers of terpinen-4-ol and of carvone equally well. Surgical lesions that removed the majority of bulbar glomeruli activated by these odorants (as demonstrated in previous olfactory bulb studies using intrinsic optical imaging and 2-deoxyglucose) resulted in increased detection thresholds but few or no deficits in discriminating between suprathreshold concentrations of the enantiomers. These results fail to confirm predictions based on 2-deoxyglucose maps of bulbar activity that enantiomers of terpinen-4-ol should be more difficult to discriminate than those of carvone and that the ability to discriminate between enantiomers of an odorant are based on differences in patterns of bulbar activation revealed in such maps.

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“…It should be further recognized that most of the animals in these studies were given smaller lesions (Lu and Slotnick, 1994;Slotnick et al, 1997), which would be predicted to spare more function. In addition, the animals were typically tested with many odorants (Lu and Slotnick, 1998), and any subsequent statistical analysis then collapsed responses across different odorants, or involved so many randomly selected odorants that the specific deficits that should have been predicted from the patterns of 2DG uptake could easily have been obscured. Analyses also were often collapsed across animals that had received lesions of various sizes and locations, potentially obscuring additional specific deficits.…”

Section: Bulbar Ablation Studiesmentioning

confidence: 99%

Chemotopic odorant coding in a mammalian olfactory system

Johnson

Leon

2007

J of Comparative Neurology

259

213

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Systematic mapping studies involving 365 odorant chemicals have shown that glomerular responses in the rat olfactory bulb are organized spatially in patterns that are related to the chemistry of the odorant stimuli. This organization involves the spatial clustering of principal responses to numerous odorants that share key aspects of chemistry such as functional groups, hydrocarbon structural elements, and/or overall molecular properties related to water solubility. In several of the clusters, responses shift progressively in position according to odorant carbon chain length. These response domains appear to be constructed from orderly projections of sensory neurons in the olfactory epithelium and may also involve chromatography across the nasal mucosa. The spatial clustering of glomerular responses may serve to "tune" the principal responses of bulbar projection neurons by way of inhibitory interneuronal networks, allowing the projection neurons to respond to a narrower range of stimuli than their associated sensory neurons. When glomerular activity patterns are viewed relative to the overall level of glomerular activation, the patterns accurately predict the perception of odor quality, thereby supporting the notion that spatial patterns of activity are the key factors underlying that aspect of the olfactory code. A critical analysis suggests that alternative coding mechanisms for odor quality, such as those based on temporal patterns of responses, enjoy little experimental support.

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Olfaction in rats with extensive lesions of the olfactory bulbs: implications for odor coding

Cited by 100 publications

References 52 publications

Adrenergic modulation of olfactory bulb circuitry affects odor discrimination

Adrenergic modulation of olfactory bulb circuitry affects odor discrimination

Discrimination between the Enantiomers of Carvone and of Terpinen-4-ol Odorants in Normal Rats and Those with Lesions of the Olfactory Bulbs

Chemotopic odorant coding in a mammalian olfactory system

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