We acknowledge all the participants, volunteers, and others involved in the study. We are grateful to Sandra Stolzenbach W&#230;hrens and Wender Bredie (University of Copenhagen) for designing the squares used in the present gratings orientation test. This research was funded by the University of Milan, Piano di sostegno alla ricerca 2018.

An informed, written consent has been signed by all participants. This study was approved by the Ethics Committee of the University of Milan (n. 48/19) and conducted in accordance with the Declaration of Helsinki.
1. Training of experimenters
<ol>
	<li>Take the grating tool and apply a force of 100 g on a sponge placed on a scale. 
	NOTE: Refer to Figure 1 for the schematic of the grating tool used in this study</li>
	<li>Repeat this procedure at least 10 t...

<ol>
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S., Van Hout, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+sensory+and+food+quality:+The+R-index+analysis.">Quantification of sensory and food quality: The R-index analysis.</a> Journal of Food Science. 74 (6), 57-64 (2009).</li><li>Bi, J., O'Mahony, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Updated+and+extended+table+for+testing+the+significance+of+the+R-index.">Updated and extended table for testing the significance of the R-index.</a> Journal of Sensory Studies. 22, 713-720 (2007).</li><li>Bertoli, S., 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=Taste+sensitivity,+nutritional+status+and+metabolic+syndrome:+Implication+in+weight+loss+dietary+interventions.">Taste sensitivity, nutritional status and metabolic syndrome: Implication in weight loss dietary interventions.</a> World Journal of Diabetes. 5 (5), 717 (2014).</li><li>Robinson, K. M., Klein, B. P., Lee, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Utilizing+the+R-index+measure+for+threshold+testing+in+model+caffeine+solutions.">Utilizing the R-index measure for threshold testing in model caffeine solutions.</a> Food Quality and Preference. 16 (4), 283-289 (2005).</li><li>Appiani, M., Rabitti, N. S., Methven, L., Cattaneo, C., Laureati, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+lingual+tactile+sensitivity+in+children+and+adults:+Methodological+suitability+and+challenges.">Assessment of lingual tactile sensitivity in children and adults: Methodological suitability and challenges.</a> Foods. 9 (11), 1594 (2020).</li><li>Cattaneo, C., Liu, J., Bech, A. C., Pagliarini, E., Bredie, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cross-cultural+differences+in+lingual+tactile+acuity,+taste+sensitivity+phenotypical+markers,+and+preferred+oral+processing+behaviors.">Cross-cultural differences in lingual tactile acuity, taste sensitivity phenotypical markers, and preferred oral processing behaviors.</a> Food Quality and Preference. 80, 103803 (2020).</li><li>Abraira, V. E., Ginty, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+sensory+neurons+of+touch.">The sensory neurons of touch.</a> Neuron. 79 (4), 618-639 (2013).</li><li>Johnson, K. O., Phillips, J. 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The authors have nothing to disclose.

Few valid instruments are available for measuring tactile acuity10,11,13,22. Von Frey filaments have been shown to be an adequate method for measuring both skin and oral tactile acuity10,21,22. However, these instruments measure a different dimension of lingual tactile acuity than the gratings orientat...

The texture and mouthfeel of food play an important role in liking1,2,3,4, and while research has found differences in texture perception due to factors such as chewing behavior2,5,&#160;saliva flow, and composition6,7, there are limited methods available to assess variation in oral tactile receptors (mechanoreceptors). The oral cavity houses different types of mechanoreceptors found in the mouth: Merkel receptors, Ruffini cylinders, and Meissner corpuscles8. Mechanoreceptors can be classed into two groups: slowly adapting and rapidly adapting. Slowly adapting mechanoreceptors (Ruffini cylinders and Merkel receptors) produce signals continuously while being stimulated. In contrast, rapidly adapting mechanoreceptors (Meissner&#39;s corpuscles) respond to the beginning and end of stimulation with a signal. Tactile acuity varies widely across tongue surfaces and between individuals, possibly due to differences in mechanoreceptor sensitivity. The location and the number of mechanoreceptors in the oral cavity, the differences in the spatial arrangement/density of the mechanoreceptors (spatial acuity), or the differences in their sensitivity when activated could be the cause of this intra- and inter-individual variability. Several methods to evaluate and screen for variation in mechanoreceptor sensitivity in the oral cavity have been published, including von Frey filaments9,10, letter recognition11,12, grating orientation tests13, and flexible electrode array14,15. The gratings orientation test requires square gratings (Figure 1, Figure 2) with different groove widths to be placed on the tongue of a blindfolded subject. They indicate if subjects perceive the gratings to be in either a horizontal or vertical orientation. Responses are used to calculate average thresholds based on the subject&#39;s ability to discriminate the orientation for the different grating sizes.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Custom-made squares</td>
			<td>University of Reading; University of Copenhagen</td>
			<td></td>
			<td>Squares of 1 cm2 from polytetrafluoroethylene (PTFE)</td>
		</tr>
		<tr>
			<td>Disinfenctant solution (20% sodium hypochlorite)</td>
			<td>Amuchina, Angelini S.p.A., Roma, Italy</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Eye masks</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gloves</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lab coat</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic cup for drinking water</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Excel</td>
			<td>Microsoft</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

assessment of spatial lingual tactile sensitivity using a gratings orientation test

Individual thresholds by R-index estimates are calculated using a gratings orientation test (6 different tools of increasing grating size from 0.20-1.25 mm) to assess spatial lingual tactile sensitivity. During the experiment, the subjects are blindfolded and asked to specify the orientation of the grating (either horizontal or vertical) placed on the tongue. R-index is based on Signal Detection Theory (SDT), and it is an estimated probability of correctly identifying a target stimulus (the signal, e.g., the correct orientation) compared to an alternative stimulus (the noise, e.g., the incorrect orientation). Once the R-index values for each subject and each tool dimension are calculated, it is possible to derive the individual threshold by interpolating the two R-indices immediately below and above the established cut-off (typically 75%) based on one-sided R-index critical values. This procedure can be helpful in the medical field to study the association between oral tactile sensitivity, speech clarity, and swallowing disorders, as well as in sensory and consumer studies to explore individual variation in texture perception, food preferences, and eating behavior.

A total of 70 healthy adults (age range = 19-33 years; mean age = 22.0; 52.9% women) were involved in the study, as shown in Appiani et al. (2020)21.
As an example, the R-index distribution by age for square 0.75 mm is reported in Figure 4. Each point represents a different subject. Subjects above the dotted line (cut-off value: 0.7426) are those who correctly identify the orientation of the grating (more sensitive).
<p class="jove_cont...

Watch this Scientific Journal Video about Assessment of Spatial Lingual Tactile Sensitivity using a Gratings Orientation Test at JoVE.com

Assessment of Spatial Lingual Tactile Sensitivity using a Gratings Orientation Test

This work illustrates a standard procedure and threshold determination by the R-index to assess spatial lingual tactile sensitivity using a gratings orientation test.

Individual thresholds by R-index estimates are calculated using a gratings orientation test (6 different tools of increasing grating size from 0.20-1.25 ...

This video illustrates a procedure to assess spatial lingual tactile size sensitivity using a grating orientation test. Similar tools have been used to measure tactile acuity at the body level, and particularly on the fingertips of the hands. However, few methodological approaches exist to measure sensitivity at the oral level.And specifically on the tongue. This procedure can be helpful in the medical feed to study the association between oral tactile sensitivity, speech clarity, and swallowing disorders, as well as in sensory consumer studies to explore individual variation in texture perception, food preferences, and eating behavior. Demonstrating the procedure will be Camilla Cattaneo post doc fellow, Marta Appiani research assistant student and Noemi Sofia Rabitti, PhD student at the university of Milan.Prior to the test, the experimenter must be trained to standardize the force applied on the subjects tongue. Take the tool and apply a force of 100 grams on a sponge placed on a scale. Display all gratings on a table.Once the participant sits on a comfortable chair, inform the participant that they can leave the experiment at any time. Inform the participant that they will be blindfolded during the experiment and asked to stick out their tongue in a comfortable and relaxed way. To familiarize the subjects with the procedure.Use the largest grating of 1.25 millimeter to demonstrate the force applied. Notify the participants that they can take a sip of water whenever deemed appropriate. Apply each grating onto the subject's tongues at the anterior region around the midline.After each touch ask the subjects to indicate the tools vertical or horizontal orientation and their degree of sureness. Subjects must guess if they do not know. After each touch, record all the answers for each subject on a spreadsheet and repeat each grating as many times as deemed necessary.Prepare a solution consisting of 20 milliliters of sodium hypochlorite diluted in one liter of water according to the manufacturer's instructions. Manually shake the solution for a few seconds, fill six cups with approximately 20 milliliters of the disinfectant solution to fully immerse each tool in the solution. Place each tool in the corresponding cup and let the tools soak for 15 to 20 minutes.Rinse the tools with plenty of water and allow the tools to air dry. Create a response matrix for each volunteer and all the tools based on the response frequencies used to calculate the R-index using the R-index equation. This is an example of a data set, for each subject the R-index values in bold are the ones used to calculate the subjects threshold by interpolating the two R indices immediately below and above the cutoff.In the current study, each grating was repeated six times and the corresponding tabulated cutoff was 0.74. The performance for the six gratings and the derived R-index threshold estimate of one subject is reported in the current study. In this case, the threshold corresponds to 0.99 millimeters.The subjects with low threshold values were able to recognize a smaller bar size and were sensitive. In comparison, the subjects with high threshold values required more input with a larger bar size to perceive the stimulus cognitively and were less sensitive. In the shown case threshold values ranged from 0.20 to 1.2 millimeters.The subjects with a threshold less than 0.20 millimeters, were able to recognize the orientation of the squares from the smallest size. Conversely, the subjects with a threshold value greater than 1.25 millimeters could not discriminate any of the grating sizes. An example of a threshold data set is represented.It is very important that the experimenters are treated and calibrated before conducting the test to ensure that a concept and standardized force is exerted on the subjects tongues. This protocol shows a new innovative way to measure lingual tactile acuity and allows us to study the association between oral tactile sensitivity, food preferences, food choices, and nutrition status.

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2.4K Views.  University of Milan. This video illustrates a procedure to assess spatial lingual tactile size sensitivity using a grating orientation test. Similar tools have been used to measure tactile acuity at the body level, and particularly on the fingertips of the hands. However, few methodological approaches exist to measure sensitivity at the oral level.And specifically on the tongue. This procedure can be helpful in the medical feed to study the association between oral tactile sensitivity, speech clarity, and ...