Detection and Masking of Spoiled Food Smells by Odor Maps in the Olfactory Bulb

Abstract

Two major causes of spoiled food smells such as fatty, fishy off-flavors are alkylamines liberated by bacterial actions and aliphatic acids-aldehydes generated by lipid oxidation. Using the method of intrinsic signal imaging, we mapped alkylamine-responsive glomeruli to a subregion of the aliphatic acid-responsive and aldehyde-responsive cluster in the odor maps of rat olfactory bulb. Extracellular single-unit recordings from mitral-tufted cells in the subregion showed that individual cells responded to the alkylamines in addition to acids and aldehydes. Responses of mitral-tufted cells tended to last for a long period (5-88 sec) even after the cessation of the alkylamine stimulation. These results suggest that the subregion is part of the representation of the fatty, fishy odor quality. Fennel and clove, spices known to add flavor and mask the fatty, fishy odor, activated glomeruli in the surrounding clusters and suppressed the alkylamineinduced and acid-aldehyde-induced responses of mitral cells, suggesting that the odor masking is mediated, in part, by lateral inhibitory connections in the odor maps of the olfactory bulb.

Functional differentiation of cholinergic and noradrenergic modulation in a biophysical model of olfactory bulb granule cells

“…On the other hand, one effect of low-concentration NE may be to limit or prevent ACh-induced persistent firing in GCs (Fig. 8C), thereby enabling persistent MC firing in response to certain odors (Takahashi et al 2004).…”

“…These neuromodulatory systems have variously been ascribed specific and often overlapping functions in sensory systems, including improving neuronal signal-to-noise ratios (SNRs), governing attentional processes and general systemic arousal, and regulating learning and memory mechanisms (Aston-Jones and Cohen 2005; Cools et al 2008;Sarter and Bruno 1997;Sarter et al 2005;Schultz et al 1997;Usher et al 1999). Achieving clear functional dissociations among the roles of these modulators in sensory processing is not trivial and warrants further investigation.…”

Visualizing odor representation in the brain: a review of imaging techniques for the mapping of sensory activity in the olfactory glomeruli

“…The threshold of activation varies among glomeruli, but all activated glomeruli show a sigmoid shaped dose-response curve when the amplitude of the signals are plotted against the log of the concentrations ranging from 0.001% up to 100% [52]. On the basis of these results, chemotopy rules for odor-elicited maps were proposed: subtle changes in odorant structure such as carbon chain length, configuration of carbon chains and functional groups led to distinct activity patterns [44,46,53]. The technique was used to study the coding and perception of enantiomers [54], odor mixture [55] and natural and territorial odorants [56,57].…”

Chemotopic odorant coding in a mammalian olfactory system

“…In other cases, however, we found stimulation of the anterior domains by methyl esters in the absence of detectable levels of acid (Johnson and Leon, unpublished observations). A subset of the glomeruli that are responsive to aliphatic acids also responds to certain primary amines as judged by optical imaging of endogenous signals (Takahashi et al, 2004b).…”