Abstract
To disentangle taste from reward responses in the human gustatory cortex, we combined high density electro-encephalography with a gustometer delivering tastant puffs to the tip of the tongue. Stimuli were pure tastants (salt solutions at two concentrations), caloric emulsions (two milk preparations identical in composition except for fat content) and a mixture of high fat milk with the lowest salt concentration. Early event-related potentials (ERPs) showed a dose-response effect for increased taste intensity, with higher amplitude and shorter latency for high compared to low salt concentration, but not for increased fat content. However, the amplitude and distribution of late potentials were modulated by fat content independently of reported intensity and discrimination. Neural source estimation revealed a sustained activation of reward areas to the two high-fat stimuli. The results suggest calorie detection through specific sensors on the tongue independent of perceived taste. Finally, amplitude variation of the first peak in the event-related potential to the different stimuli correlated with papilla density, suggesting a higher discrimination power for subjects with more fungiform papillae.
Highlights
Why is fatty food so appealing? Just as carbohydrates, minerals and proteins, fatty acids are essential to proper functioning of the body and survival
The amplitude of event-related potentials (ERPs) measured after High Salt and Low Salt stimulations revealed three periods of significant differences (t-test, >20 ms, P < 0.01) corresponding to each peak of the gustatory ERP previously described (Mizoguchi et al, 2002; Ohla et al, 2010)
Pleasantness ratings clustered the stimuli into three groups, with the highest pleasantness for the two milks followed by FatSalt and the two pleasant salt solutions
Summary
Why is fatty food so appealing? Just as carbohydrates, minerals and proteins, fatty acids are essential to proper functioning of the body and survival. Texture is not the only cue: olfaction contributes to the detection of fatty acids in animals, evidence in humans is still controversial (Mattes, 2009). A diverse group of primary signal transduction molecules (i.e., fat taste receptors) has been described in the membranes of lingual tissue cells (Mattes, 2010). Some of these mechanisms have been linked to human perception of fatty acids, preference or obesity (Galindo et al, 2012; Ichimura et al, 2012; Pepino et al, 2012), no conclusive evidence has been obtained for a fatty taste signal transduction mechanism in humans. The role of the induced sensations in humans could rather be to prevent ingestion of dangerous food than to support their selection (Drewnowski and Almiron-Roig, 2010; Mattes, 2011)
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