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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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Cerebral glucose metabolism (CGM) differences obtained for the FLiCl flavour compared to the FGlu flavour. (A) Three-dimensional skinned representation of the pig’s brain with global CGM differences found in the FLiClvs FGlu contrast. The (x y z) coordinates are indicated below the representation. (B) Sagittal and coronal MRI sections showing significant CGM differences in the FLiClvs FGlu contrast. The threshold for significance was set at P<0.05 (uncorrected). The x or y coordinates are indicated below each section. Positive t-values (green, yellow and red) indicate more activation in the FLiCl condition than in the FGlu condition, while negative t-values (blue and purple) indicate more deactivation in the FLiCl condition than in the FGlu condition. F, Front; B, Back; R, Right; L, Left; IC, insular cortex; ITG, inferior temporal cortex. Other abbreviations: see Figure 5.
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pone-0037968-g006: Cerebral glucose metabolism (CGM) differences obtained for the FLiCl flavour compared to the FGlu flavour. (A) Three-dimensional skinned representation of the pig’s brain with global CGM differences found in the FLiClvs FGlu contrast. The (x y z) coordinates are indicated below the representation. (B) Sagittal and coronal MRI sections showing significant CGM differences in the FLiClvs FGlu contrast. The threshold for significance was set at P<0.05 (uncorrected). The x or y coordinates are indicated below each section. Positive t-values (green, yellow and red) indicate more activation in the FLiCl condition than in the FGlu condition, while negative t-values (blue and purple) indicate more deactivation in the FLiCl condition than in the FGlu condition. F, Front; B, Back; R, Right; L, Left; IC, insular cortex; ITG, inferior temporal cortex. Other abbreviations: see Figure 5.

Mentions: The APFC was significantly less activated in the FLiCl condition than in the FNaCl (Figure 5) or FGlu (Figure 6) conditions, and the OFC in the FLiCl condition than in the FNaCl condition. Conversely, the PHC, the posterior cingulate cortex (PCC) and the AMY were more activated, while the anterior cingulate cortex (ACC) and the CI were globally less activated in the FLiCl condition than in the FNaCl or FGlu conditions. As for the basal nuclei, the right NAcc, GP and PUT were more activated, whereas the left PUT and GP were less activated in the FLiCl condition than in the FNaCl or FGlu conditions. The right CAU was also more activated in the FLiCl – FGlu contrast (Figure 6). Compared to FNaCl and FGlu, the perception of FLiCl induced higher CGM responses in the left (superior, middle and inferior) temporal gyrus.


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)

Cerebral glucose metabolism (CGM) differences obtained for the FLiCl flavour compared to the FGlu flavour. (A) Three-dimensional skinned representation of the pig’s brain with global CGM differences found in the FLiClvs FGlu contrast. The (x y z) coordinates are indicated below the representation. (B) Sagittal and coronal MRI sections showing significant CGM differences in the FLiClvs FGlu contrast. The threshold for significance was set at P<0.05 (uncorrected). The x or y coordinates are indicated below each section. Positive t-values (green, yellow and red) indicate more activation in the FLiCl condition than in the FGlu condition, while negative t-values (blue and purple) indicate more deactivation in the FLiCl condition than in the FGlu condition. F, Front; B, Back; R, Right; L, Left; IC, insular cortex; ITG, inferior temporal cortex. Other abbreviations: see Figure 5.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368353&req=5

pone-0037968-g006: Cerebral glucose metabolism (CGM) differences obtained for the FLiCl flavour compared to the FGlu flavour. (A) Three-dimensional skinned representation of the pig’s brain with global CGM differences found in the FLiClvs FGlu contrast. The (x y z) coordinates are indicated below the representation. (B) Sagittal and coronal MRI sections showing significant CGM differences in the FLiClvs FGlu contrast. The threshold for significance was set at P<0.05 (uncorrected). The x or y coordinates are indicated below each section. Positive t-values (green, yellow and red) indicate more activation in the FLiCl condition than in the FGlu condition, while negative t-values (blue and purple) indicate more deactivation in the FLiCl condition than in the FGlu condition. F, Front; B, Back; R, Right; L, Left; IC, insular cortex; ITG, inferior temporal cortex. Other abbreviations: see Figure 5.
Mentions: The APFC was significantly less activated in the FLiCl condition than in the FNaCl (Figure 5) or FGlu (Figure 6) conditions, and the OFC in the FLiCl condition than in the FNaCl condition. Conversely, the PHC, the posterior cingulate cortex (PCC) and the AMY were more activated, while the anterior cingulate cortex (ACC) and the CI were globally less activated in the FLiCl condition than in the FNaCl or FGlu conditions. As for the basal nuclei, the right NAcc, GP and PUT were more activated, whereas the left PUT and GP were less activated in the FLiCl condition than in the FNaCl or FGlu conditions. The right CAU was also more activated in the FLiCl – FGlu contrast (Figure 6). Compared to FNaCl and FGlu, the perception of FLiCl induced higher CGM responses in the left (superior, middle and inferior) temporal gyrus.

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