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Scientists Find Why Sweet and Salty Pair So Sweetly
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Purposes: Information storage and access Personalisation. Legitimate Interest Purposes: Ad selection, delivery, reporting Content selection, delivery, reporting Measurement. Over the last decade, research challenging the notion has been piling up. Today, savory, also called umami, is widely recognized as a basic taste, the fifth. And now other candidates, perhaps as many as 10 or 20, are jockeying for entry into this exclusive club.
Mattes , a professor of nutrition science at Purdue University. Taste plays an intrinsic role as a chemical-sensing system for helping us find what is nutritious stimulatory and as a defense against what is poison aversive. When we put food in our mouths, chemicals slip over taste buds planted into the tongue and palate. In the late s, in a windowless laboratory at Brooklyn College, the psychologist Anthony Sclafani was investigating the attractive power of sweets.
His lab rats loved Polycose, a maltodextrin powder, even preferring it to sugar. That was puzzling for two reasons: Maltodextrin is rarely found in plants that rats might feed on naturally, and when human subjects tried it, the stuff had no obvious taste. More than a decade later, a team of exercise scientists discovered that maltodextrin improved athletic performance — even when the tasteless additive was swished around in the mouth and spit back out. Our tongues report nothing; our brains, it seems, sense the incoming energy.
Sclafani said. The tips where positioned comfortably between the lips such that the tubes delivered the stimuli on the front of the tongue. The pumps were programmed to administer 1 mL of solution in 2. Also, VAS ratings of intensity and pleasantness were made during the scan by use of a custom-built button box. Timeline of one cycle of tasting during an fMRI run. Left in figure cues shown to the subject during the trail. In a pilot study, 10 solutions of sucrose in water and 10 solutions of NaCl in water ranging from 0 to 1.
The 4 concentrations chosen for both sucrose and NaCl were 0, 0. The total duration of each functional run was 21 min, during which scans were obtained. First, the functional volumes of every subject were realigned to the first volume of the first run. Next, the anatomical image was coregistered with the mean functional image. A statistical parametric map was generated for every subject by fitting a boxcar function to each time series, convolved with the canonical hemodynamic response function.
Data were high-pass filtered with a cutoff of s.
For every subject, 2 types of analyses were performed: 1 parametric modulation analyses and 2 analyses of taste activation. Because pleasantness and intensity are closely related Veldhuizen et al. The responses to swallowing, rinsing, and rating were modeled but were not included in further analyses. The contrast images for linear parametric modulation of taste activation by subjective intensity ratings and by concentration were calculated for both sessions sucrose and NaCl. The responses to swallowing, rinsing, and rating were not included in further analyses.
In summary, these analyses yielded 2 modulation contrast images for modulation by concentration and by subjective intensity and 4 taste activation contrast images zero, low, middle, and high intensity per subject per session. The motion correction parameters from the realignment procedure were added to all models as regressors to regress out motion-related variance.
For the group analyses, the modulation contrast images of both sessions of all subjects were entered into a paired t -test. Two paired t -tests were done using the parametric modulation contrast images: one with the contrast images of modulation by intensity ratings and one with the contrast images of modulation by concentration. Per subject 8 mean parameter estimates were calculated one for every concentration in the 2 taste sessions. Parameter estimates were normalized per subject by using the parameter estimate of the zero concentration as a baseline measurement.
These regions have been shown to respond to differences in taste Small et al. The subjective ratings obtained during the scans were analyzed as follows: Mean intensity ratings were calculated per condition sucrose and NaCl and per concentration 0, 0. Subsequently, these average intensity ratings were compared between the sweet and the salty session with paired t -tests, for every concentration. The same was done for the mean pleasantness ratings.
The correlation r between the subjective intensity ratings and the given concentration were also calculated.
Sweet, sour, salty, bitter – and savory
Statistical analyses of the subjective ratings were done with SPSS Intensity and pleasantness ratings are shown in Figure 2. Higher concentrations of both tastes were rated as more intense. Mean sweet intensities ratings were at 1. Mean pleasantness ratings dropped with increasing concentration for both tastes as shown in Figure 2 right panel Mean saltiness: 5. Mean sweetness ratings were 5. Correlation between VAS ratings of stimulus intensity and concentration of tastes solutions.
This figure appears in color in the online version of Chemical Senses. When combining response to sweet and salty taste, taste activation in the middle insula was modulated by concentration, as well by intensity ratings bilaterally.
The Science of Taste
Taste activation in the right amygdala and right putamen covaried with concentration but not with perceived intensity. This is shown in Table 1. Brain regions where taste activation is modulated by intensity and concentration of taste a. Taste intensity modulation was tested by performing a t -test on the contrast images of modulation of taste activation by intensity ratings and concentration for all brain voxels by using statistical parametric mapping.
L, left: R, right; ROI. Voxel coordinates are in MNI space Evans et al. Brain regions whose response covaried with NaCl intensity ratings and NaCl concentration are shown in Table 2. In the NaCl condition, taste activation was modulated by intensity ratings in the middle insula bilaterally , right amygdala, left hippocampus, right putamen, and in the caudate bilaterally. Activation in the middle insula bilaterally , right amygdala, and the right putamen was modulated by NaCl concentration. Positive modulation of taste activation in the middle insula by NaCl concentration and intensity ratings is shown in detail in Figure 4.
Modulation of amygdala taste activation by NaCl concentration and intensity is shown in Figure 5. Brain regions where taste activation is modulated by the degree of saltiness a. Saltiness modulation was tested by performing a t -test on the contrast images for modulation of taste activation by intensity ratings and concentration for all brain voxels by using statistical parametric mapping. Modulation of insula taste activation by saltiness. Circles indicate the insula clusters. Modulation of amygdala taste activation by saltiness. Bottom: mean parameter estimates of taste activation for the amygdala peak voxels per concentration.
Circles indicate the amygdala cluster. Modulation of insula taste activation by sweetness.
Scientists Find Why Sweet and Salty Pair So Sweetly
Circles indicate the insula cluster. Bottom: mean parameter estimates of taste activation for the insula peak voxel per concentration. Brain regions whose response covaried with sweet intensity ratings and sucrose concentration are shown in Table 3. Modulation of taste activation by sweet intensity ratings was found in the right middle insula Figure 6. Also, in the left thalamus modulation of taste activation by sweetness was found. Taste activation in the right middle insula and in the right putamen was positively modulated by sucrose concentration Table 3.
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Taste activation in the amygdala was not modulated by sucrose concentration or perceived sweetness intensity. Brain regions where taste activation is modulated by the degree of sweetness a. Sweetness modulation was tested by performing a t -test on the contrast images of modulation of taste activation by intensity ratings and concentration for all brain voxels by using statistical parametric mapping. Modulation of taste activation in the anterior insula was stronger from saltiness than from sweetness, that is, anterior insula activation increased more with NaCl concentration then with sucrose concentration.
There were no brain areas that were modulated more strongly by sucrose concentration than by NaCl concentration. Brain regions where taste activation is differentially modulated by sweetness and saltiness a. Modulation was tested by performing a t -test on the contrast images of modulation of taste activation by intensity ratings and concentration for all brain voxels by using statistical parametric mapping. We determined the brain areas where taste activation covaries with stimulus intensity, using a range of NaCl and sucrose solutions.
Perceived intensity and concentration were highly correlated and therefore modulation by these 2 factors yielded similar brain areas. The first study examining the representation of taste intensity in the brain compared brain responses between 2 low intensity tastes and 2 high intensity tastes sweet and bitter Small et al. This classical fMRI approach compares taste activation, that is, how robustly tasting induces a blood oxygen level—dependent BOLD response.
In contrast, we used parametric modulation analyses in conjunction with a range of 4 concentrations of each stimulus type. Parametric modulation is a more recently developed approach Buchel et al.
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