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Sniff adjustment in an odor discrimination task in the rat: analytical or synthetic strategy?

Courtiol E, Lefèvre L, Garcia S, Thévenet M, Messaoudi B, Buonviso N - Front Behav Neurosci (2014)

Bottom Line: We found that sniffing variations were not only a matter of odorant sorption properties and that the same odorant was sniffed differently depending on the odor pair in which it was presented.These results suggest that rather than being adjusted analytically, sniffing is instead adjusted synthetically and depends on the pair of odorants presented during the discrimination task.Our results show that sniffing is a specific sensorimotor act that depends on complex synthetic processes.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Neurosciences de Lyon, Equipe Olfaction: du codage à la mémoire, CNRS UMR 5292-INSERM U1028-Université Lyon1 Lyon, France.

ABSTRACT
A growing body of evidence suggests that sniffing is not only the mode of delivery for odorant molecules but also contributes to olfactory perception. However, the precise role of sniffing variations remains unknown. The zonation hypothesis suggests that animals use sniffing variations to optimize the deposition of odorant molecules on the most receptive areas of the olfactory epithelium (OE). Sniffing would thus depend on the physicochemical properties of odorants, particularly their sorption. Rojas-Líbano and Kay (2012) tested this hypothesis and showed that rats used different sniff strategies when they had to target a high-sorption (HS) molecule or a low-sorption (LS) molecule in a binary mixture. Which sniffing strategy is used by rats when they are confronted to discrimination between two similarly sorbent odorants remains unanswered. Particularly, is sniffing adjusted independently for each odorant according to its sorption properties (analytical processing), or is sniffing adjusted based on the pairing context (synthetic processing)? We tested these hypotheses on rats performing a two-alternative choice discrimination of odorants with similar sorption properties. We recorded sniffing in a non-invasive manner using whole-body plethysmography during the behavioral task. We found that sniffing variations were not only a matter of odorant sorption properties and that the same odorant was sniffed differently depending on the odor pair in which it was presented. These results suggest that rather than being adjusted analytically, sniffing is instead adjusted synthetically and depends on the pair of odorants presented during the discrimination task. Our results show that sniffing is a specific sensorimotor act that depends on complex synthetic processes.

No MeSH data available.


Enantiomers are sniffed similarly. (A) Global sampling parameters (mean ± s.e.m.), Sd (left) and Ns (right), for each odorant in each enantiomer odor pair: L-car (magenta)/D-car (red) n = 195; L-lim (cyan)/D-lim (dark blue) n = 211. (B) Modulation of sniff parameters in the first, second, and third cycles for (left to right) L-car/D-car and L-lim/D-lim. From top to bottom: mean (± s.e.m.) normalized ID, IPF, and ED. Same colors as in (A). The number of trials for each odorant and cycle in L-car/D-car pair is: ncycle 1 = 195, ncycle 2 = 188, and ncycle 3 = 175 and in L-lim/D-lim pair is: ncycle 1 = 211, ncycle 2 = 201, and ncycle 3 = 162. Data were analyzed using a paired t-test; *p < 0.05; and **p < 0.01.
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Figure 3: Enantiomers are sniffed similarly. (A) Global sampling parameters (mean ± s.e.m.), Sd (left) and Ns (right), for each odorant in each enantiomer odor pair: L-car (magenta)/D-car (red) n = 195; L-lim (cyan)/D-lim (dark blue) n = 211. (B) Modulation of sniff parameters in the first, second, and third cycles for (left to right) L-car/D-car and L-lim/D-lim. From top to bottom: mean (± s.e.m.) normalized ID, IPF, and ED. Same colors as in (A). The number of trials for each odorant and cycle in L-car/D-car pair is: ncycle 1 = 195, ncycle 2 = 188, and ncycle 3 = 175 and in L-lim/D-lim pair is: ncycle 1 = 211, ncycle 2 = 201, and ncycle 3 = 162. Data were analyzed using a paired t-test; *p < 0.05; and **p < 0.01.

Mentions: For the two pairs of enantiomers we tested (LS/LS and HS/HS pairs), the global sampling parameters were similar; animals sniffed these enantiomers with a similar Sd and a similar Ns [Figure 3A, Sd: L-car/D-car pair t(194) = −0.323, p = 0.74; L-lim/D-lim pair t(210) = −0.085, p = 0.93, Ns: L-car/D-car pair t(194) < 0.001, p > 0.05; L-lim/D-lim pair t(210) = −0.592, p = 0.56]. Similarly, an analysis of the fine sniffing parameters revealed few or no significant differences between enantiomeric odorants, regardless of the sorption properties, as shown in Figure 3B. For the L-car/D-car pair (Figure 3B, left), a significant difference appeared only in the ID during the second cycle [t(187) = 2.994, p < 0.01] and in the IPF during the first cycle [t(194) = −2.044, p < 0.05]. We also observed few differences between L-lim and D-lim (Figure 3B, right) with a significant difference only in the ID during the second cycle [t(200) = 2.207, p < 0.05]. Thus, very similar molecules, such as the two pairs of enantiomers tested, induce similar sniffing strategies.


Sniff adjustment in an odor discrimination task in the rat: analytical or synthetic strategy?

Courtiol E, Lefèvre L, Garcia S, Thévenet M, Messaoudi B, Buonviso N - Front Behav Neurosci (2014)

Enantiomers are sniffed similarly. (A) Global sampling parameters (mean ± s.e.m.), Sd (left) and Ns (right), for each odorant in each enantiomer odor pair: L-car (magenta)/D-car (red) n = 195; L-lim (cyan)/D-lim (dark blue) n = 211. (B) Modulation of sniff parameters in the first, second, and third cycles for (left to right) L-car/D-car and L-lim/D-lim. From top to bottom: mean (± s.e.m.) normalized ID, IPF, and ED. Same colors as in (A). The number of trials for each odorant and cycle in L-car/D-car pair is: ncycle 1 = 195, ncycle 2 = 188, and ncycle 3 = 175 and in L-lim/D-lim pair is: ncycle 1 = 211, ncycle 2 = 201, and ncycle 3 = 162. Data were analyzed using a paired t-test; *p < 0.05; and **p < 0.01.
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Figure 3: Enantiomers are sniffed similarly. (A) Global sampling parameters (mean ± s.e.m.), Sd (left) and Ns (right), for each odorant in each enantiomer odor pair: L-car (magenta)/D-car (red) n = 195; L-lim (cyan)/D-lim (dark blue) n = 211. (B) Modulation of sniff parameters in the first, second, and third cycles for (left to right) L-car/D-car and L-lim/D-lim. From top to bottom: mean (± s.e.m.) normalized ID, IPF, and ED. Same colors as in (A). The number of trials for each odorant and cycle in L-car/D-car pair is: ncycle 1 = 195, ncycle 2 = 188, and ncycle 3 = 175 and in L-lim/D-lim pair is: ncycle 1 = 211, ncycle 2 = 201, and ncycle 3 = 162. Data were analyzed using a paired t-test; *p < 0.05; and **p < 0.01.
Mentions: For the two pairs of enantiomers we tested (LS/LS and HS/HS pairs), the global sampling parameters were similar; animals sniffed these enantiomers with a similar Sd and a similar Ns [Figure 3A, Sd: L-car/D-car pair t(194) = −0.323, p = 0.74; L-lim/D-lim pair t(210) = −0.085, p = 0.93, Ns: L-car/D-car pair t(194) < 0.001, p > 0.05; L-lim/D-lim pair t(210) = −0.592, p = 0.56]. Similarly, an analysis of the fine sniffing parameters revealed few or no significant differences between enantiomeric odorants, regardless of the sorption properties, as shown in Figure 3B. For the L-car/D-car pair (Figure 3B, left), a significant difference appeared only in the ID during the second cycle [t(187) = 2.994, p < 0.01] and in the IPF during the first cycle [t(194) = −2.044, p < 0.05]. We also observed few differences between L-lim and D-lim (Figure 3B, right) with a significant difference only in the ID during the second cycle [t(200) = 2.207, p < 0.05]. Thus, very similar molecules, such as the two pairs of enantiomers tested, induce similar sniffing strategies.

Bottom Line: We found that sniffing variations were not only a matter of odorant sorption properties and that the same odorant was sniffed differently depending on the odor pair in which it was presented.These results suggest that rather than being adjusted analytically, sniffing is instead adjusted synthetically and depends on the pair of odorants presented during the discrimination task.Our results show that sniffing is a specific sensorimotor act that depends on complex synthetic processes.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Neurosciences de Lyon, Equipe Olfaction: du codage à la mémoire, CNRS UMR 5292-INSERM U1028-Université Lyon1 Lyon, France.

ABSTRACT
A growing body of evidence suggests that sniffing is not only the mode of delivery for odorant molecules but also contributes to olfactory perception. However, the precise role of sniffing variations remains unknown. The zonation hypothesis suggests that animals use sniffing variations to optimize the deposition of odorant molecules on the most receptive areas of the olfactory epithelium (OE). Sniffing would thus depend on the physicochemical properties of odorants, particularly their sorption. Rojas-Líbano and Kay (2012) tested this hypothesis and showed that rats used different sniff strategies when they had to target a high-sorption (HS) molecule or a low-sorption (LS) molecule in a binary mixture. Which sniffing strategy is used by rats when they are confronted to discrimination between two similarly sorbent odorants remains unanswered. Particularly, is sniffing adjusted independently for each odorant according to its sorption properties (analytical processing), or is sniffing adjusted based on the pairing context (synthetic processing)? We tested these hypotheses on rats performing a two-alternative choice discrimination of odorants with similar sorption properties. We recorded sniffing in a non-invasive manner using whole-body plethysmography during the behavioral task. We found that sniffing variations were not only a matter of odorant sorption properties and that the same odorant was sniffed differently depending on the odor pair in which it was presented. These results suggest that rather than being adjusted analytically, sniffing is instead adjusted synthetically and depends on the pair of odorants presented during the discrimination task. Our results show that sniffing is a specific sensorimotor act that depends on complex synthetic processes.

No MeSH data available.