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Exposures to conditioned flavours with different hedonic values induce contrasted behavioural and brain responses in pigs.

Clouard C, Jouhanneau M, Meunier-Salaün MC, Malbert CH, Val-Laillet D - PLoS ONE (2012)

Bottom Line: Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference.As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus.In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices.

View Article: PubMed Central - PubMed

Affiliation: INRA, UR1341 ADNC (Alimentation & Adaptations Digestives, Nerveuses et Comportementales), Saint Gilles, France.

ABSTRACT
This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (F(Glu)), lithium chloride (F(LiCl)), or saline (control treatment, F(NaCl)). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three (18)FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the F(LiCl) than the F(NaCl) or F(Glu) meals. During the two-choice tests performed one and five weeks later, the F(NaCl) and F(Glu) foods were significantly preferred over the F(LICl) food even in the absence of i.d. infusions. Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.

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Related in: MedlinePlus

Experimental device and paradigm designed to perform olfactogustatory stimulations for brain imaging in anaesthetised pigs.The illustrations used to make this figure were obtained from the “Servier Medical Art” website, http://www.servier.fr/servier-medical-art.
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pone-0037968-g001: Experimental device and paradigm designed to perform olfactogustatory stimulations for brain imaging in anaesthetised pigs.The illustrations used to make this figure were obtained from the “Servier Medical Art” website, http://www.servier.fr/servier-medical-art.

Mentions: The olfactogustatory stimulation was performed with computer-assisted automats designed in our laboratory (Figure 1). The olfactory stimulation consisted in diffusing a nonodorized or an odorized air (0.05% essential oil) into the pig’s right nostril (4 L/min). As the animals were intubated and mechanically ventilated, the diffused air could not come out from the mouth. Consequently, the olfactory stimulation was performed via one of the two nostrils to let the air flow through the nasal cavity. The choice to perform the stimulation via the right nostril rather than the left nostril, however, has been done arbitrarily. A tube was inserted in the right nostril of the animal and connected to a device composed of a medical air cylinder connected to a flow meter and a two-way circuit of bottles equipped with a system of electronic valves. One of the bottles contained unodorized tap water and the other contained odorized water (0.05% essential oil). The gustatory stimulation consisted in irrigating the pig’s tongue (24 mL/min) with an unflavoured or a flavoured artificial saliva (0.05% essential oil; for the saliva composition, see [44]). A tube was positioned on the middle of the tongue and connected to a computer-operated automat developed in our laboratory (Gustautomat, INRA, St Gilles, France, see [29]) and inspired by the Taste–o–Matic designed by Hellekant’s group [45]. The animals were subjected to a neutral olfactogustatory stimulation (i.e., nonodorized air and unflavoured saliva) for 5 min to accommodate the mucosa thermoreceptors and mechanoreceptors to the stimulation. Then, the diffusion of odorized air and flavoured saliva was performed for 15 min. The stimulation was ended by a 15-min neutral stimulation.


Exposures to conditioned flavours with different hedonic values induce contrasted behavioural and brain responses in pigs.

Clouard C, Jouhanneau M, Meunier-Salaün MC, Malbert CH, Val-Laillet D - PLoS ONE (2012)

Experimental device and paradigm designed to perform olfactogustatory stimulations for brain imaging in anaesthetised pigs.The illustrations used to make this figure were obtained from the “Servier Medical Art” website, http://www.servier.fr/servier-medical-art.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368353&req=5

pone-0037968-g001: Experimental device and paradigm designed to perform olfactogustatory stimulations for brain imaging in anaesthetised pigs.The illustrations used to make this figure were obtained from the “Servier Medical Art” website, http://www.servier.fr/servier-medical-art.
Mentions: The olfactogustatory stimulation was performed with computer-assisted automats designed in our laboratory (Figure 1). The olfactory stimulation consisted in diffusing a nonodorized or an odorized air (0.05% essential oil) into the pig’s right nostril (4 L/min). As the animals were intubated and mechanically ventilated, the diffused air could not come out from the mouth. Consequently, the olfactory stimulation was performed via one of the two nostrils to let the air flow through the nasal cavity. The choice to perform the stimulation via the right nostril rather than the left nostril, however, has been done arbitrarily. A tube was inserted in the right nostril of the animal and connected to a device composed of a medical air cylinder connected to a flow meter and a two-way circuit of bottles equipped with a system of electronic valves. One of the bottles contained unodorized tap water and the other contained odorized water (0.05% essential oil). The gustatory stimulation consisted in irrigating the pig’s tongue (24 mL/min) with an unflavoured or a flavoured artificial saliva (0.05% essential oil; for the saliva composition, see [44]). A tube was positioned on the middle of the tongue and connected to a computer-operated automat developed in our laboratory (Gustautomat, INRA, St Gilles, France, see [29]) and inspired by the Taste–o–Matic designed by Hellekant’s group [45]. The animals were subjected to a neutral olfactogustatory stimulation (i.e., nonodorized air and unflavoured saliva) for 5 min to accommodate the mucosa thermoreceptors and mechanoreceptors to the stimulation. Then, the diffusion of odorized air and flavoured saliva was performed for 15 min. The stimulation was ended by a 15-min neutral stimulation.

Bottom Line: Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference.As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus.In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices.

View Article: PubMed Central - PubMed

Affiliation: INRA, UR1341 ADNC (Alimentation & Adaptations Digestives, Nerveuses et Comportementales), Saint Gilles, France.

ABSTRACT
This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (F(Glu)), lithium chloride (F(LiCl)), or saline (control treatment, F(NaCl)). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three (18)FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the F(LiCl) than the F(NaCl) or F(Glu) meals. During the two-choice tests performed one and five weeks later, the F(NaCl) and F(Glu) foods were significantly preferred over the F(LICl) food even in the absence of i.d. infusions. Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.

Show MeSH
Related in: MedlinePlus