Awards from the National Institutes of Health supported this research (R01DC013588 to NAC, R21DC013886 to NAC and DRR, and NIDCD Administrative Research Supplement to Promote Emergence of Clinician-Scientists in Chemosensory Research to JED). We collected genotype data from equipment purchased in part with NIH funds from OD018125.

The University of Pennsylvania Institutional Review board approved this protocol. We excluded subjects if they were under 18 years of age or were pregnant.
1. Oral Cavity Evaluation: Disease Assessment and Papilla Identification
<ol>
	<li>Instruct the subject to open the mouth.</li>
	<li>Using a light source such as a penlight or headlamp, illuminate the oral cavity and examine the seven subsites of the area (tongue, floor of mouth, buccal mucosa, labial mucosa, gingiva, hard palate, and retromolar trigone).
	<ol>
		<li>Visualize the dorsal surface of the tongue. Instruct the subject to lift up the tongue, and examine the ventral tongue surface and floor of mouth, making sure to extend the examination posteriorly to the molars.</li>
		<li>Using a tongue depressor, lateralize the subject&#39;s cheek to visualize the buccal mucosa, as well as the lateral gingiva bilaterally surrounding the upper and lower teeth.</li>
		<li>Extend the examination anteriorly by lifting the upper and lower lips to visualize the surfaces of the labial mucosal and anterior gingiva.</li>
		<li>Finally, visualize the hard palate and retromolar trigone.</li>
		<li>Note lesions, abrasions, and masses or signs of inflammation.</li>
		<li>Again, ask the subject to open the mouth and extend the tongue.</li>
		<li>Use a light source to visualize the dorsal surface of the tongue.</li>
		<li>Identify the presence or absence of FP, e.g., a smooth tongue surface</li>
	</ol>
	</li>
	<li>Note the results of the oral cavity examination before proceeding with taste testing. If investigators conduct this taste test in a medical context, unexpected findings should prompt further work-up.</li>
</ol>
2. Psychophysical Taste Testing
NOTE: Resources and descriptions for the psychophysical taste testing that follow are also available from the following web page: https://osf.io/hn87s/.
<ol>
	<li>Tastant preparation
	<ol>
		<li>Prepare solutions as directed below. Make each solution using a volumetric flask to ensure precision of concentrations to &#177; 0.0002 M. Dissolve samples using ultrapure water. Tailor the choice of compounds to the research goals. The compounds included here are meant as one example.
		<ol>
			<li>Denatonium benzoate (bitter): prepare a stock solution of 4.99 x 10-3 M denatonium benzoate by dissolving 2.228 g of denatonium benzoate in 1 L of water. Add 180 &#181;L of this stock solution to a 500 mL volumetric flask. Add water to bring the volume to 500 mL, producing a solution with a final concentration of 1.8 &#181;M.</li>
			<li>PTC (bitter): Place 0.0135 g of PTC in a 500 mL volumetric flask. Add water to bring the volume to 500 mL. PTC is difficult to dissolve, so place a stir bar in the flask and heat the solution to 70 &#176;C on a hot plate. Use the stir bar to mix the solution until all solute has dissolved (~15 min). This produces a solution with a final concentration of 180 &#181;M.</li>
			<li>Quinine (bitter): Place 0.011 g of quinine HCl dihydrate in a 500 mL volumetric flask. Add water to bring the volume to 500 mL, producing a solution with a final concentration of 56 &#181;M.</li>
			<li>Sodium chloride (salty): Place 7.5 g of sodium chloride in a 500 mL volumetric flask. Add water to bring the volume to 500 mL, producing a solution with a final concentration of 0.25 M.</li>
			<li>Sucrose (sweet): Place 60 g of sucrose in a 500 mL volumetric flask. Add water to bring the volume to 500 mL, producing a solution with a final concentration of 0.35 M.</li>
		</ol>
		</li>
		<li>Store taste solutions at 4 &#176;C. Some commonly used taste compounds are light-sensitive, and investigators should wrap them in foil or other materials to reduce their exposure to light.</li>
		<li>To identify common errors in solution preparation, fill one tasting cup with the old solution and one with the new solution. Taste each solution to verify they are identical in strength.</li>
		<li>Include water as a control solution, presented in the first position to verify subjects understand the testing procedure. Present subjects with each tastant and the control tastant twice, taking care to avoid presenting the same tastant consecutively. For example, to test five unique tastants, feature twelve samples in the questionnaire (see 2.2): the five tastants and water, each presented twice. Aliquot 5 mL of water into individual glass scintillation vials. Label the vial caps with a dark blue sticker bearing the number 1.</li>
		<li>Repeat this process for each tastant. Label vial caps with a circular sticker according to the order of presentation and some color code, example detailed below; match the vial labels with the labels on the taste questionnaire (see 2.2). 
		Water (dark blue) 
		Quinine (light blue) 
		NaCl (green) 
		PTC (yellow) 
		Sucrose (orange) 
		Denatonium benzoate (red) 
		NaCl (dark blue) 
		Denatonium benzoate (light blue) 
		Water (green) 
		Quinine (yellow) 
		Sucrose (orange) 
		PTC (red)</li>
		<li>Package samples by placing them into two boxes, samples 1&#8211;6 and 7&#8211;12 in boxes labeled &#34;box A&#34; and &#34;box B,&#34; respectively (Figure 1); other packaging strategies are possible.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56705/56705fig1v2.jpg" /> 
Figure 1: Taste kit. Subjects use the kit to rate taste intensity and quality of various color-coded tastants. Box A contains samples 1&#8211;6, box B contains 7&#8211;12. <a href="/files/ftp_upload/56705/56705fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Taste questionnaire
	<ol>
		<li>Prepare the taste questionnaire using a category scale for rating taste intensity and a forced choice for identifying the taste quality of each tastant (Figure 2).</li>
		<li>Place circular labels of the appropriate color and number next to the appropriate sample in the taste questionnaire (see 2.1.6).</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56705/56705fig2.jpg" /> 
Figure 2: Taste questionnaire entry, comprising a category scale for intensity rating and forced choice response for tastant quality. The taste questionnaire will include one entry for each of the color-coded tastants tested. <a href="/files/ftp_upload/56705/56705fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>Taste Test Administration
	<ol>
		<li>Provide subjects with box A, box B, a bottle of water, empty cup, pen, and pen-and-paper taste questionnaire containing entries for 12 samples. Use the same brand of bottled water throughout the duration of any given study. As an alternative to a paper questionnaire, port the material into online survey software and administered via tablet or desktop/Laptop. A sample template is available at https://osf.io/hn87s/.</li>
		<li>Instruct subjects that they will be asked to rate both the intensity and quality (e.g., salty, sour, bitter, sweet, or no flavor) of each tastant. Also, inform subjects they may not experience all qualities.</li>
		<li>Explain the testing procedure, as follows: Rinse your mouth twice with water and spit it out in the cup provided. Pour all of sample 1 into your mouth and hold it there for 5 seconds before spitting the solution into the cup. Do not gargle or swallow the solution. Circle one of the 13 vertical lines corresponding with the sample&#39;s intensity, on a scale of 0 to 12, from &#34;no intensity at all&#34; to &#34;extremely intense&#34; and choose a single quality to describe the taste. Afterward, rinse your mouth with water twice before proceeding to the next sample.</li>
		<li>Observe the subject tasting and rating sample 1 (water). Should the rating deviate from &#34;no intensity at all&#34; and &#34;no flavor,&#34; reiterate the questionnaire instructions before allowing the test to proceed.</li>
		<li>Review the finished questionnaire for completeness.</li>
		<li>Score intensity ratings on a scale of 0 to 12 from the vertical lines that the subjects circled. Average the two intensity ratings for each tastant; this value will be used for analysis.</li>
	</ol>
	</li>
</ol>
3. Genotype
<ol>
	<li>Collect saliva from each subject using a saliva DNA collection kit.</li>
	<li>Purify genomic DNA from the sample by following manufacturer instructions.</li>
	<li>Determine TAS2R38 genotype using SNP genotyping assays (rs713598,rs1726866, rs10246939)40.</li>
	<li>Determine TAS2R19 genotype using SNP genotyping assays (rs10772420)36.</li>
</ol>
4. Genotype-phenotype Validation
<ol>
	<li>Review the available pooled control data from over 800 subjects genotyped for TAS2R38 (rs713598, rs1726866, rs10246939) and TAS2R19 (rs10772420) at the following web page: https://carayata.shinyapps.io/TasteBoxplots/.</li>
	<li>Based on a subject&#39;s TAS2R38 genotype, compare his or her psychophysical taste response for the bitter compound PTC with the norms for individuals of the same genotype. Responses should match; however, in rare cases, TAS2R38 genotype does not perfectly predict PTC sensory results35.</li>
	<li>Should responses show significant divergence, compare the subject&#39;s taste response for quinine with the norms for individuals of the same TAS2R19 genotype. Responses for quinine intensity and genotype should match36.&#160;Should all taste results fail to correspond with genotype, it is possible that the subject (a) does not understand the task (b) is providing spurious ratings or malingering or (c) there has been an data collection error on the part of the investigator.</li>
	<li>Identify data point outliers, and perhaps exclude them from analysis (Figure 3). Correspondence of sensory results with objective genotyping validates the reliability of the psychophysical testing procedure.</li>
</ol>

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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+in+the+TAS2R31+bitter+taste+receptor+gene+relates+to+liking+for+the+nonnutritive+sweetener+Acesulfame-K+among+children+and+adults.">Variation in the TAS2R31 bitter taste receptor gene relates to liking for the nonnutritive sweetener Acesulfame-K among children and adults.</a> Science Reports. 6, 39135 (2016).</li><li>Allen, A. L., McGeary, J. E., Knopik, V. S., Hayes, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bitterness+of+the+non-nutritive+sweetener+acesulfame+potassium+varies+with+polymorphisms+in+TAS2R9+and+TAS2R31.">Bitterness of the non-nutritive sweetener acesulfame potassium varies with polymorphisms in TAS2R9 and TAS2R31.</a> Chemical Senses. 38 (5), 379-389 (2013).</li><li>Roudnitzky, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic,+genetic,+and+functional+dissection+of+bitter+taste+responses+to+artificial+sweeteners.">Genomic, genetic, and functional dissection of bitter taste responses to artificial sweeteners.</a> Human Molecular Genetics. 20 (17), 3437-3449 (2011).</li><li>Guo, S. W., Reed, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetics+of+phenylthiocarbamide+perception.">The genetics of phenylthiocarbamide perception.</a> Annals in Human Biology. 28 (2), 111-142 (2001).</li><li>Bartoshuk, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Labeled+scales+(e.g.,+category,+Likert,+VAS)+and+invalid+across-group+comparisons:+what+we+have+learned+from+genetic+variation+in+taste.">Labeled scales (e.g., category, Likert, VAS) and invalid across-group comparisons: what we have learned from genetic variation in taste.</a> Food Quality Prefererences. 14 (2), 125-138 (2003).</li></ol>

NAC and DRR are co-inventors on a patent under review (Therapy and Diagnostics for Respiratory Infection 61/697,652, WO2013112865).

The significance of this method is that it uses a multidisciplinary approach with features from medicine (the oral exam), experimental psychology (the taste test) and genetics (a validation step). Taste information is likely to develop as a diagnostic and prognostic tool because taste provides a window into the function of proteins elsewhere in the body. From an experimental psychology viewpoint, the addition of a simple exam can identify subjects who are not appropriate for the study of normative taste function. From a ...

Measures of human taste perception can be both part of medical care and a target of biomedical research, yet taste has received scant attention compared with hearing and vision (Table 1). From the medical perspective, when clinicians evaluate patients complaining of taste loss, in most cases the actual loss is of smell1, which has led to dismissal of taste loss as an uncommon and often invalid presenting complaint. Taste distortions (dysgeusia) are more common and frequently arise from the secondary effects of medications or peripheral nerve injury2,3, but neither form has an effective treatment (other than stopping the medication). Clinicians have also ignored taste loss because it has hitherto had little diagnostic or prognostic value on its own. However, although the measurement of taste has been a backwater, it may now be entering mainstream medicine with the revival of a historical appreciation that taste may be a diagnostic or prognostic tool4,5. For instance, bitterness perception can predict immune function6 or the willingness of a patient to take medication7. Nonetheless, biomedical researchers have largely neglected taste. This inattention may, in part, reflect the fact that early progress in understanding this sensory system has its roots in experimental psychology8, a field with which those in medicine may be relatively unfamiliar. Moreover, renewed interest in taste has ushered in standardized taste methods9 that build on earlier methods10, which while comprehensive are lengthy and inappropriate for clinical settings. Finally, confidence in taste measures can be weak because subjects report on their own experience and validation of their observations has hitherto been lacking. Our hope is that a simple measure that investigators or clinicians can easily administer will gain in popularity with both constituents. Here we describe a simple taste exam protocol that has three parts: an assessment of the oral cavity, the taste test, and a validation step using inborn genotype. First, we provide biological context for these procedures, which merge simple practices in medicine, sensory measures from experimental psychology and validation of responses using genotype and genetics.
Taste perception starts in the mouth, so an effective taste exam needs to include a brief clinical assessment for obvious oral diseases, redness, swelling and other discoloration. The oral cavity contains seven subsites: the tongue, gingiva, floor of mouth, buccal mucosa, labial mucosa, hard palate, and the retromolar trigone. Past studies of human taste focused on healthy participants or those with well-defined diseases, but as taste testing becomes routine in medical exams, it is important to record the condition of the oral cavity as part of the procedure.
The tongue itself is a muscular structure encased in mucosa; dotting its dorsal surface are papillae, the small raised structures that give the tongue its unique texture and contain taste receptor cells. We classify papillae by their shape: fungiform, filiform, foliate, and circumvallate. Fungiform papillae (FP) are located anterolaterally on the tongue and are round, with a mushroom shape11. Investigators have published several useful methods to quantify FP and we direct readers to these sources for measurement protocols12,13,14,15,16. Foliate papillae, shaped like the pages of a book (folia), are located exclusively on the lateral posterior tongue surface11. Circumvallate papillae, found in the sulcus terminalis of the tongue base, are large dome-shaped structures surrounded by mucosal walls (Latin circum, &#34;surround,&#34; + vallum, &#34;wall&#34;)11. The most numerous papillae, the filiform, are long and thin and do not contain taste receptors.
People differ in tongue anatomy. While the sources of this anatomic variation are unknown, it is determined in part by inborn genetic variation, with investigators reporting 31% concordance of tongue anatomy among dizygotic twins and 60% concordance among monozygotic twins17. Papillary density also differs among people, and although rare, at least one genetic disease (familial dysautonomia) results in a congenital absence of taste papillae18,19,20. Thus, before performing psychophysical testing, it is helpful to confirm the presence of FP as part of the brief assessment and note the relative size and color of the tongue and evidence of oral disease.
The taste papillae contain the sensory cells that when stimulated initiate taste sensation. Humans are capable of sensing at least five classes of taste: salty, sour, bitter, sweet, and umami. While salty, sweet, and umami tastes signal the presence of valuable food sources containing sodium chloride, glucose, and amino acids, respectively, bitterness and sourness signal the presence of potential toxins and acids from the bacterial decomposition of food, respectively, and induce aversive behavior21. Salty and sour tastes are transduced through the activation of ion channels found in some types of taste cells, though the understanding of salt transduction is evolving and it may require type I cells as well22,23. Bitter, sweet, and umami arise from activation of G-protein-coupled receptors on type II taste cells, each attuned to a particular taste. Heterodimers of subunits of three particular receptors transduce sweet and umami while bitter compounds activate a group of 25 different bitter receptors24. These bitter receptors can respond to multiple bitter compounds, and a single bitter compound often stimulates more than one receptor25. Despite the recent expansion of knowledge about the molecular basis of taste, novel pathways26 and new discoveries beyond the traditional five taste qualities (e.g., calcium27 or fatty acid28 perception) may lie ahead.
There are at least two surprising aspects of the taste families of receptors: genes that code for these receptors can differ markedly in DNA sequence and hence function among people, and many tissues of the body express these genes21,29,30,31. These extraoral sites include the brain, thyroid, upper and lower respiratory tract, and the gastrointestinal tract, among many others21,29,30,31. While the taste receptors at these locations do not participate in taste perception in the traditional sense, they likely sense the local chemical environment29,32. For example, the ciliated epithelium of the upper respiratory tract expresses the bitter receptor T2R38 (Bitter Taste Receptor 38), which responds to chemical compounds produced by bacteria and influences the innate immune response32, such as increasing mucociliary clearance and levels of anti-microbial peptides and nitric oxide. This finding has medical implications for chronic rhinosinusitis, a disease of chronic bacterial infection and inflammation of the upper respiratory tract and paranasal sinuses.
Of particular relevance to the taste exam we describe here is that the T2R38 bitter taste receptor, encoded by the TAS2R38 gene, exhibits genetic variability and therefore variable taste sensitivity. Perceptual differences for the bitter compound phenylthiocarbamide (PTC) were first described by the chemist Arthur Fox33; later this compound was identified as an agonist of the T2R38 receptor34. Individual differences arise from the DNA sequence of the TAS2R38 gene, which has three single-nucleotide polymorphisms, each yielding amino acid substitutions (A49P, A262V, and I296V; A: Alanine, P: Proline, V: Valine, I: Isoleucine). Two common haplotypes result, PAV and AVI, with PAV/PAV individuals being highly sensitive to PTC (&#34;tasters&#34;), AVI/AVI individuals being relatively insensitive (&#34;non-tasters&#34;), and heterozygous AVI/PAV individuals being more variable in their sensitivity35. There are more examples of genetic variation affecting bitter perception, e.g., taste receptor T2R19, encoded by the TAS2R19 gene, similarly exhibits genetic variability and differing taste sensitivity to the bitter compound quinine36. Likewise, variation in TAS2R31 affects the perceived bitterness of one of the high-potency sweeteners37,38,39.
Here we describe a rapid method to characterize a patient&#39;s sense of taste that draws on high-yield protocols in clinical medicine, experimental psychology and genetics.

<table><tbody><tr><td>Disposable diagnostic penlight</td><td>Primacare</td><td>DL-9223</td><td></td></tr><tr><td>UltraLite Pro headlight</td><td>Integra LifeSciences</td><td>AX2100BIF</td><td></td></tr><tr><td>Millipore Q-Gard 2 water purification system</td><td>EMB Millipore</td><td>QGARD00D2</td><td></td></tr><tr><td>Denatonium benzoate&amp;nbsp;</td><td>Sigma Aldrich</td><td>D5765</td><td></td></tr><tr><td>Phenylthiocarbamide</td><td>Sigma Aldrich</td><td>P7629</td><td></td></tr><tr><td>Quinine hydrochloride dihydrate</td><td>Sigma Aldrich</td><td>Q1125</td><td></td></tr><tr><td>Sodium Chloride</td><td>Sigma Aldrich</td><td>S1679</td><td></td></tr><tr><td>Sucrose</td><td>Sigma Aldrich</td><td>S0389</td><td></td></tr><tr><td>Glass scintillation vials</td><td>Thomas Scientific</td><td>1230L59</td><td>Same as Wheaton catalog no. 986580</td></tr><tr><td>Oragene Discover OGR-500 DNA collection kit</td><td>DNA Genotek</td><td>OGR-500</td><td></td></tr><tr><td>prepIT L2P Protocol reagents</td><td>DNA Genotek</td><td>PT-L2P-5</td><td></td></tr><tr><td>&lt;em&gt;rs713598 &lt;/em&gt;TaqMan SNP genotyping assay</td><td>ThermoFisher Scientific</td><td>C___8876467_10</td><td></td></tr><tr><td>&lt;em&gt;rs1726866 &lt;/em&gt;TaqMan SNP genotyping assay</td><td>ThermoFisher Scientific</td><td>C___9506827_10</td><td></td></tr><tr><td>&lt;em&gt;rs10246939 &lt;/em&gt;TaqMan SNP genotyping assay</td><td>ThermoFisher Scientific</td><td>C___9506826_10</td><td></td></tr><tr><td>&lt;em&gt;rs10772420 &lt;/em&gt;TaqMan SNP genotyping assay</td><td>ThermoFisher Scientific</td><td>C___1317426_10</td><td></td></tr></tbody></table>

taste exam: a brief and validated test

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement classic taste-testing methods in two ways. First, we explain how to do a brief assessment of the mouth, including the tongue, to ensure that taste papillae are present and to note evidence of relevant disease. Second, we draw on genetics to validate taste test data by comparing reports of perceived bitterness intensity and inborn receptor genotypes. Discordance between objective measures of genotype and subjective reports of taste experience can identify data collection errors, distracted subjects or those who have not understood or followed instructions. Our expectation is that fast and valid taste tests may persuade researchers and clinicians to assess taste regularly, making taste testing as common as testing for hearing and vision. Finally, because many tissues of the body express taste receptors, taste responses may provide a proxy for tissue sensitivity elsewhere in the body and, thereby, serve as a rapid, point-of-care test to guide diagnosis and a research tool to evaluate taste receptor protein function.

Results from the taste test have been pooled for all subjects evaluated (n = 840) and are presented after segregation by genotype. The full data set is accessible at https://carayata.shinyapps.io/TasteBoxplots/ and can be reviewed for each tastant assessed and for TAS2R38 and TAS2R19 genotypes. Results confirm the existence of perceptual taste differences for PTC among subjects grouped by TAS2R38 receptor genotype (Figure 3). Rating...

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Taste Exam: A Brief and Validated Test

This protocol measures human taste responses and includes a brief anatomical assessment, a short taste test, and a validation method using the subject&#39;s reported sensation and taste receptor genotype.

The emerging importance of taste in medicine and biomedical research, and new knowledge about its genetic underpinnings, has motivated us to supplement ...

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Medicine

16.2K Views.  Perelman School of Medicine at the University of Pennsylvania. This protocol measures human taste responses and includes a brief anatomical assessment, a short taste test, and a validation method using the subject's reported sensation and taste receptor genotype.

Video: Taste Exam: A Brief and Validated Test

Examination of Rapid Dopamine Dynamics with Fast Scan Cyclic Voltammetry During Intra-oral Tastant Administration in Awake Rats

Rapid, phasic dopamine (DA) release in the mammalian brain plays a critical role in reward processing, reinforcement learning, and motivational control. Fast scan cyclic voltammetry (FSCV) is an electrochemical technique with high spatial and temporal (sub-second) resolution that has been utilized to examine phasic DA release in several types of preparations. In vitro experiments in single-cells and brain slices and in vivo experiments in anesthetized rodents have been used to identify mechanisms that mediate dopamine release and uptake under normal conditions and in disease models. Over the last 20 years, in vivo FSCV experiments in awake, freely moving rodents have also provided insight of dopaminergic mechanisms in reward processing and reward learning. One major advantage of the awake, freely moving preparation is the ability to examine rapid DA fluctuations that are time-locked to specific behavioral events or to reward or cue presentation. However, one limitation of combined behavior and voltammetry experiments is the difficulty of dissociating DA effects that are specific to primary rewarding or aversive stimuli from co-occurring DA fluctuations that mediate reward-directed or other motor behaviors. Here, we describe a combined method using in vivo FSCV and intra-oral infusion in an awake rat to directly investigate DA responses to oral tastants. In these experiments, oral tastants are infused directly to the palate of the rat &#8211; bypassing reward-directed behavior and voluntary drinking behavior &#8211; allowing for direct examination of DA responses to tastant stimuli.

Rapid fluctuations in extracellular dopamine (DA) mediate both reward processing and motivated behavior in mammals. This manuscript describes the combined use of fast scan cyclic voltammetry (FSCV) and intra-oral tastant administration to determine how tastants alter rapid dopamine release in awake, freely moving rats.

Rapid, phasic dopamine (DA) release in the mammalian brain plays a critical role in reward processing, reinforcement learning, and motivational control. ...

Behavior

Protocol for Data Collection and Analysis Applied to Automated Facial Expression Analysis Technology and Temporal Analysis for Sensory Evaluation

We demonstrate a method for capturing emotional response to beverages and liquefied foods in a sensory evaluation laboratory using automated facial expression analysis (AFEA) software. Additionally, we demonstrate a method for extracting relevant emotional data output and plotting the emotional response of a population over a specified time frame. By time pairing each participant's treatment response to a control stimulus (baseline), the overall emotional response over time and across multiple participants can be quantified. AFEA is a prospective analytical tool for assessing unbiased response to food and beverages. At present, most research has mainly focused on beverages. Methodologies and analyses have not yet been standardized for the application of AFEA to beverages and foods; however, a consistent standard methodology is needed. Optimizing video capture procedures and resulting video quality aids in a successful collection of emotional response to foods. Furthermore, the methodology of data analysis is novel for extracting the pertinent data relevant to the emotional response. The combinations of video capture optimization and data analysis will aid in standardizing the protocol for automated facial expression analysis and interpretation of emotional response data.

A protocol for capturing and statistically analyzing emotional response of a population to beverages and liquefied foods in a sensory evaluation laboratory using automated facial expression analysis software is described.

We demonstrate a method for capturing emotional response to beverages and liquefied foods in a sensory evaluation laboratory using automated facial ...

Psychophysical Tracking Method to Measure Taste Preferences in Children and Adults

The Monell two-series, forced-choice, paired-comparison tracking method provides a reliable measure of sweet taste preferences from childhood to adulthood. The method, which is identical for children, adolescents, and adults, is of short duration (&#60; 15 min), does not rely on sustained attention or place demands on memory (which would yield spurious age differences), and minimizes the impact of language development, making this method amenable to the cognitive limitations of pediatric populations. In this whole-mouth tasting method, subjects are asked to taste (without swallowing) pairs of solutions of different sucrose concentrations and to point to the solution they prefer. Each subsequent pair contains the participant&#39;s preceding preferred concentration and an adjacent stimulus concentration. The procedure continues until the subject chooses either a given concentration of sucrose when paired with both a higher and a lower concentration, or the highest or lowest concentration two consecutive times. Subjects are prevented from reaching response criteria on the basis of first or second position bias by the two-series design of the method, which counterbalances the order of solution presentation within each pair between the series (the weaker concentration is presented first in Series 1, second in Series 2). The geometric mean of the two sucrose concentrations chosen in Series 1 and 2 is an estimate of the participant&#39;s most preferred level of sucrose. Sucrose preference as determined with this laboratory-based measure has been shown to be associated with preference for sugars in foods and beverages and with taste receptor genotype, family history of alcoholism, and race/ethnicity, as well as depressive symptomatology among pediatric populations. The method has real-world relevance and has been applied to determine most preferred level of other tastes (e.g., salt), making it a valuable psychophysical tool.

Sweet taste has powerful hedonic appeal among people of all ages, particularly children. Described herein is a reliable and valid method that can be used to determine the level of sweetness most preferred, making it a valuable psychophysical tool for scientists.

The Monell two-series, forced-choice, paired-comparison tracking method provides a reliable measure of sweet taste preferences from childhood to ...

Measuring Oral Fatty Acid Thresholds, Fat Perception, Fatty Food Liking, and Papillae Density in Humans

Emerging evidence from a number of laboratories indicates that humans have the ability to identify fatty acids in the oral cavity, presumably via fatty acid receptors housed on taste cells. Previous research has shown that an individual&#39;s oral sensitivity to fatty acid, specifically oleic acid (C18:1) is associated with body mass index (BMI), dietary fat consumption, and the ability to identify fat in foods. We have developed a reliable and reproducible method to assess oral chemoreception of fatty acids, using a milk and C18:1 emulsion, together with an ascending forced choice triangle procedure. In parallel, a food matrix has been developed to assess an individual&#39;s ability to perceive fat, in addition to a simple method to assess fatty food liking. As an added measure tongue photography is used to assess papillae density, with higher density often being associated with increased taste sensitivity.

Oral chemoreception of fatty acids and the association with diet and fatty food preferences may enable the identification of mechanisms involved with the development of obesity and why dietary changes may be difficult for many individuals.

Emerging evidence from a number of laboratories indicates that humans have the ability to identify fatty acids in the oral cavity, presumably via fatty ...

Neuroscience

Taste Preference Assay for Adult Drosophila

Olfactory and gustatory perception of the environment is vital for animal survival. The most obvious application of these chemosenses is to be able to distinguish good food sources from potentially dangerous food sources. Gustation requires physical contact with a chemical compound which is able to signal through taste receptors that are expressed on the surface of neurons. In insects, these gustatory neurons can be located across the animal's body allowing taste to play an important role in many different behaviors. Insects typically prefer compounds containing sugars, while compounds that are considered bitter tasting are avoided. Given the basic biological importance of taste, there is intense interest in understanding the molecular mechanisms underlying this sensory modality. We describe an adult Drosophila taste assay which reflects the preference of the animals for a given tastant compound. This assay may be applied to animals of any genetic background to examine the taste preference for a desired soluble compound.

Taste Preference Assay for Adult Drosophila

Taste is an important sensory process which facilitates attraction to beneficial substances and avoidance of toxic substances. This protocol describes a simple ingestion assay for determining Drosophila gustatory preference for a given chemical compound.

Olfactory and gustatory perception of the environment is vital for animal survival.  The most obvious application of these chemosenses is to be able to ...

New Methods to Study Gustatory Coding

The sense of taste allows animals to detect chemicals in the environment, giving rise to behaviors critical for survival. When Gustatory Receptor Neurons (GRNs) detect tastant molecules, they encode information about the identity and concentration of the tastant as patterns of electrical activity that then propagate to follower neurons in the brain. These patterns constitute internal representations of the tastant, which then allow the animal to select actions and form memories. The use of relatively simple animal models has been a powerful tool to study basic principles in sensory coding. Here, we propose three new methods to study gustatory coding using the moth Manduca sexta. First, we present a dissection procedure for exposing the maxillary nerves and the subesophageal zone (SEZ), allowing recording of the activity of GRNs from their axons. Second, we describe the use of extracellular electrodes to record the activity of multiple GRNs by placing tetrode wires directly into the maxillary nerve. Third, we present a new system for delivering and monitoring, with high temporal precision, pulses of different tastants. These methods allow the characterization of neuronal responses in vivo directly from GRNs before, during and after tastants are delivered. We provide examples of voltage traces recorded from multiple GRNs, and present an example of how a spike sorting technique can be applied to the data to identify the responses of individual neurons. Finally, to validate our recording approach, we compare extracellular recordings obtained from GRNs with tetrodes to intracellular recordings obtained with sharp glass electrodes.

We present three new methods to study gustatory coding. Using a simple animal, the moth Manduca sexta (Manduca), we describe a dissection protocol, the use of extracellular tetrodes to record the activity of multiple gustatory receptor neurons, and a system for delivering and monitoring precisely timed pulses of tastants.

The sense of taste allows animals to detect chemicals in the environment, giving rise to behaviors critical for survival. When Gustatory Receptor Neurons ...

A Rapid Food-Preference Assay in Drosophila

To select food with nutritional value while avoiding the consumption of harmful agents, animals need a sophisticated and robust taste system to evaluate their food environment. The fruit fly, Drosophila melanogaster, is a genetically tractable model organism that is widely used to decipher the molecular, cellular, and neural underpinnings of food preference. To analyze fly food preference, a robust feeding method is needed. Described here is a two-choice feeding assay, which is rigorous, cost-saving, and fast. The assay is Petri-dish-based and involves the addition of two different foods supplemented with blue or red dye to the two halves of the dish. Then, ~70 prestarved, 2-4-day-old flies are placed in the dish and&#160;allowed to choose between blue and red foods in the dark for about 90 min. Examination of the abdomen of each fly is followed by the calculation of the preference index. In contrast to multiwell plates, each Petri dish takes only ~20 s to fill and saves time and effort. This feeding assay can be employed to quickly determine whether flies like or dislike a particular food.

A Rapid Food-Preference Assay in Drosophila

We present a protocol for a two-choice feeding assay for flies. This feeding assay is fast and easy to run and is suitable not only for small-scale laboratory research, but also for high-throughput behavioral screens in flies.

To select food with nutritional value while avoiding the consumption of harmful agents, animals need a sophisticated and robust taste system to evaluate ...

Whole-Mount Staining, Visualization, and Analysis of Fungiform, Circumvallate, and Palate Taste Buds

Taste buds are collections of taste-transducing cells specialized to detect subsets of chemical stimuli in the oral cavity. These transducing cells communicate with nerve fibers that carry this information to the brain. Because taste-transducing cells continuously die and are replaced throughout adulthood, the taste-bud environment is both complex and dynamic, requiring detailed analyses of its cell types, their locations, and any physical relationships between them. Detailed analyses have been limited by tongue-tissue heterogeneity and density that have significantly reduced antibody permeability. These obstacles require sectioning protocols that result in splitting taste buds across sections so that measurements are only approximated, and cell relationships are lost. To overcome these challenges, the methods described herein involve collecting, imaging, and analyzing whole taste buds and individual terminal arbors from three taste regions: fungiform papillae, circumvallate papillae, and the palate. Collecting whole taste buds reduces bias and technical variability and can be used to report absolute numbers for features including taste-bud volume, total taste-bud innervation, transducing-cell counts, and the morphology of individual terminal arbors. To demonstrate the advantages of this method, this paper provides comparisons of taste bud and innervation volumes between fungiform and circumvallate taste buds using a general taste-bud marker and a label for all taste fibers. A workflow for the use of sparse-cell genetic labeling of taste neurons (with labeled subsets of taste-transducing cells) is also provided. This workflow analyzes the structures of individual taste-nerve arbors, cell type numbers, and the physical relationships between cells using image analysis software. Together, these workflows provide a novel approach for tissue preparation and analysis of both whole taste buds and the complete morphology of their innervating arbors.

This paper describes methods for tissue preparation, staining, and analysis of whole fungiform, circumvallate, and palate taste buds that consistently yield whole and intact taste buds (including the nerve fibers that innervate them) and maintain the relationships between structures within taste buds and the surrounding papilla.

Taste buds are collections of taste-transducing cells specialized to detect subsets of chemical stimuli in the oral cavity. These transducing cells ...

&#181;Tongue: A Microfluidics-Based Functional Imaging Platform for the Tongue In Vivo

Intravital fluorescence microscopy is a tool used widely to study multicellular dynamics in a live animal. However, it has not been successfully used in the taste sensory organ. By integrating microfluidics into the intravital tongue imaging window, the &#181;Tongue provides reliable functional images of taste cells in vivo under controlled exposure to multiple tastants. In this paper, a detailed step-by-step procedure to utilize the &#181;Tongue system is presented. There are five subsections: preparing of tastant solutions, setting up of a microfluidic module, sample mounting, acquiring functional image data, and data analysis. Some tips and techniques to solve the practical issues that may arise when using the &#181;Tongue are also presented.

 &#181;Tongue: A Microfluidics-Based Functional Imaging Platform for the Tongue In Vivo

The article introduces the &#181;Tongue (microfluidics-on-a-tongue) device for functional taste cell imaging in vivo by integrating microfluidics into an intravital imaging window on the tongue.

Intravital fluorescence microscopy is a tool used widely to study multicellular dynamics in a live animal. However, it has not been successfully used in ...

Psychophysical Tracking Method to Assess Taste Detection Thresholds in Children, Adolescents, and Adults: The Taste Detection Threshold (TDT) Test

This paper describes a two-alternative, forced-choice, staircase, tracking procedure, called the Taste Detection Threshold (TDT) test, that provides a reliable measure of sweet, salty, and umami taste detection thresholds from childhood to adulthood. Advantages of the method include procedures that are identical for children and adults, thus allowing the determination of age-related and individual differences in taste perception, if any, and tasks that can be completed in a relatively short time frame, do not rely on continuous attention or require memorization, control for subjective response biases, and minimize the impact of language development. After a 1 hour fast, participants are presented with pairs of solutions; in each pair, one solution is water, and the other solution contains varying concentrations of the tastant.
Using a whole-mouth tasting method, participants taste each solution (without swallowing and with rinsing between tastings) and then point to the solution with a taste or that tastes different from water. The concentration of the stimulus in the subsequent pair increases after a single incorrect response and decreases after two consecutive correct responses. A reversal occurs when the concentration sequence changes direction. The task is deemed completed after the occurrence of four reversals, provided there are a maximum of two dilution steps between two successive reversals, and the series of reversals do not form an ascending pattern. These additional criteria ensure greater reliability in outcomes. The TDT is then calculated as the geometric mean of the concentrations of the four reversals. This method has real-world relevance as it provides information on a dimension of taste perception that is independent of hedonics, and that can change with aging and certain disease states, making it a valuable psychophysical test.

Psychophysical Tracking Method to Assess Taste Detection Thresholds in Children, Adolescents, and Adults: The Taste Detection Threshold TDT Test

Psychophysical tools measure the functionality of the taste system for both research and health assessment purposes. This paper describes a method to measure taste detection thresholds that can determine the lowest concentration of sucrose, sodium chloride, or monosodium glutamate that can be tasted by individuals as young as 6 years.

This paper describes a two-alternative, forced-choice, staircase, tracking procedure, called the Taste Detection Threshold (TDT) test, that provides a ...

Taste Exam: A Brief and Validated Test

Summary

Explore More Videos

Chapters in this video

Examination of Rapid Dopamine Dynamics with Fast Scan Cyclic Voltammetry During Intra-oral Tastant Administration in Awake Rats

Protocol for Data Collection and Analysis Applied to Automated Facial Expression Analysis Technology and Temporal Analysis for Sensory Evaluation

Psychophysical Tracking Method to Measure Taste Preferences in Children and Adults

Measuring Oral Fatty Acid Thresholds, Fat Perception, Fatty Food Liking, and Papillae Density in Humans

Taste Preference Assay for Adult Drosophila

New Methods to Study Gustatory Coding

A Rapid Food-Preference Assay in Drosophila

Whole-Mount Staining, Visualization, and Analysis of Fungiform, Circumvallate, and Palate Taste Buds

µTongue: A Microfluidics-Based Functional Imaging Platform for the Tongue In Vivo

Psychophysical Tracking Method to Assess Taste Detection Thresholds in Children, Adolescents, and Adults: The Taste Detection Threshold (TDT) Test