(tongue map, mouth map)
Six common errors: Criticism of the human tongue maps as seen in some text books:
1) Areas of sensitivity are shown schematically on the tongue, but the
scientific source is not referenced. To provide
a reference is important, also because sources do not necessarily agree. For instance, ref.  places the minimal threshold
for bitter towards the vallate (posterior tongue), while ref.  places it towards the anterior tongue. (Note, however, that
the first investigator measured detection thresholds, the second recognition thresholds and sensation magnitudes.)
2) When compared to the original (where the source is provided), the areas shown are distorted.
3) The areas are claimed to be "areas of preference". They are not,
because in studies like , no comparison of intensity
of sensation across taste qualities was made. Instead, thresholds of single qualities are compared across areas. In other cases,
areas may depict the intensity of sensation of one quality (rather than the threshold).
4) Differences are not appraised in a quantitative way. In the work
of ref. , the detection threshold for sucrose was determined
to 10 mM at the tip of the tongue and 35 mM in the vallate zone. This difference is not large when compared to the concentration
range in which the intensity of sucrose taste increases. By dropping the quantitative aspect, these small differences were later blown
up to "areas of preference" in text books as well as in recent scientific publications.
5) Merely "significant overlap" between areas is conceded. This is not
enough. According to Hänig  and Collings , each
of the human taste areas responds to all (4 in these cases) taste qualities tested (100% overlap).
6) The center of the dorsal surface of the human tongue should not be
shown to have appreciable taste sensitivity. As early as 1875,
A. Hoffmann concluded that the dorsal center of the human tongue has practically no fungiform papillae and taste buds .
In agreement, Hänig talks of a "taste belt" running around the rim of the tongue and along the vallate papillae. This belt contains
the sensitive areas while the center of the dorsal surface is spared out . Taste properties of the palate and of the area caudal
of the vallate papilla should not be ignored.
click here to see the original
tongue map by D. P. Hänig (1901):
Chemotopic organization in the rat:
In the rat, contrary to humans (and hamsters), the nerve response to
sucrose is larger when sucrose is applied at the posterior
tongue, as compared to the anterior tongue . The palate has the highest sweet-sensitivity in the rat, the anterior tongue the lowest.
In rats and hamster, the anterior tongue and the palate have a pronounced sensitivity to NaCl which can be blocked by oral amiloride .
In the posterior tongue, responses to NaCl can be blocked by amiloride in the hamster, but not in the rat .
References on the chemotopic organization in different mammals (emphasis on sweet and bitter):
HUMAN: [1, 2, 6-13]
HUMAN reviewed: [14-16]
RAT: [5, 17-27]
RODENTS reviewed: [4, 31-34]
DOG: [35, 36]
References on thresholds and related concepts of psychophysics:
1. Hänig, D.P., 1901. Zur Psychophysik des Geschmackssinnes.
Philosophische Studien, 17: 576-623.
2. Collings, V.B., 1974. Human Taste Response as a Function of Locus of Stimulation on the Tongue and Soft Palate. Perception & Psychophysics, 16: 169-174.
3. Hoffmann, A., 1875. Über die Verbreitung der Geschmacksknospen beim Menschen. Arch. Pathol. Anat. Physiol., 62: 516-530.
4. Smith, D.V. and M.E. Frank, 1993. Sensory Coding by Peripheral Taste Fibers, in Chapter 12: Mechanisms of Taste Transduction, S.A. Simon and S.D. Roper, Editor. CRC Press: Boca Raton. 295-338.
5. Kitada, Y., Y. Mitoh, and D.L. Hill, 1998. Salt taste responses of the IXth nerve in Sprague-Dawley rats: Lack of sensitivity to amiloride. Physiol Behav, 63(5): 945-949.
6. Kiesow, F., 1892. Beiträge zur physiologischen Psychologie des Geschmacksinnes (a). Philosophische Studien, 10: 329-368.
7. Shore, L.A., 1892. A contribution to our knowledge of taste sensations. Journal of Physiology, 13: 191-217.
8. Henkin, R.I., J.R. Gill, Jr., and F.C. Bartter, 1963. Studies on Taste Thresholds in Normal Man and in Patients with Adrenal Cortical Insufficiency: The Role of Adrenal Cortical Steroids and of Serum Sodium Concentration. Journal of Clinical Investigation, 42: 727-735.
9. Amerine, M.A., R.M. Pangborn, and E.B. Roessler, 1965. Principles of Sensory Evaluation of Food. New York: Academic. 144.
10. Henkin, R.I. and R.L. Christiansen, 1967. Taste Localization on the Tongue, Palate and Pharynx of Normal Man. Journal of Applied Physiology, 22: 316-320.
11. Henkin, R.I., P.P.G. Graziadei, and D.F. Bradley, 1969. The Molecular Basis of Taste and its Disorders (NIH Clinical Staff Conference). Annals of Internal Medicine, 71: 791-821.
12. Sandick, B. and A.V. Cardello, 1981. Taste Profiles from Single Circumvallate Papillae: Comparison with Fungiform Profiles. Chemical Senses, 6: 197-214.
13. Miller, I.J. and F.E.J. Reedy, 1990. Variations in Human Taste Bud Density and Taste Intensity Perception. Physiology & Behavior, 47: 1213-1219.
14. Bartoshuk, L.M., 1978. History of Taste Research, in Handbook of Perception, E.C. Carterette and M.P. Friedman, Editor. Academic Press: N.Y. 3 - 16.
15. Bartoshuk, L.M., 1993. The biological basis of food perception and acceptance. Food Quality and Preference, 4: 21-32.
16. Bartoshuk, L.M., 1993. Genetic and pathological taste variation: What can we learn from animal models and human disease? Ciba Foundation Symposium, 179: 251-267.
17. Oakley, B., 1967. Altered Temperature and Taste Responses from Cross- Regenerated Sensory Nerves in the Rat's Tongue. Journal of Physiology, 188: 353-371.
18. Travers, S.P., C. Pfaffmann, and R. Norgren, 1986. Convergence of Lingual and Palatal Gustatory Neural Activity in the Nucleus of the Solitary Tract. Brain Res., 365: 305 - 320.
19. Nejad, M.S., 1986. The neural activities of the greater superficial petrosal nerve of the rat in response to chemical stimulation of the palate. Chem. Senses, 11: 283-293.
20. Krimm, R.F., M.S. Nejad, J.C. Smith, I.J.J. Miller, and L.M. Beidler, 1987. The effect of bilateral sectioning of the chorda tympani and the greater superficial petrosal
nerves on the sweet taste in the rat. Physiol Behav, 41: 495-501.
21. Boudreau, J.C., L.T. Do, L. Sivakumar, J. Oravec, and C.A. Rodriguez, 1987. Taste Systems of the Petrosal Ganglion of the Rat Glossopharyngeal Nerve. Chemical Senses, 12: 437-458.
22. Frank, M.E., 1991. Taste-Responsive Neurons of the Glossopharyngeal Nerve of the Rat. J. Neurophysiol., 65: 1452-1463.
23. Travers, S.P. and R. Norgern, 1991. Coding the sweet taste in the nucleus of the solitary tract: differential roles for anterior tongue and nasoincisor duct gustatory receptors in the rat. J. Neurophysiol., 65: 1372-.
24. Formaker, B.K. and D.L. Hill, 1991. Lack of Amiloride Sensitivity in SHR and WKY Glossopharyngeal Taste Responses to NaCl. Physiology and Behavior, 50: 765-769.
25. Spector, A.C., R. Redman, and M. Garcea, 1996. The consequences of gustatory nerve transection on taste-guided licking of sucrose and maltose in the rat. Behav. Neurosci, 110(5): 1096-1109.
26. Sollars, S.I. and D.L. Hill, 1998. Taste responses in the greater superficial petrosal nerve: substantial sodium salt and amiloride sensitivities
demonstrated in two rat strains. Behav. Neurisci., 112: 991-1000.
27. St. John, S.J. and A.C. Spector, 1998. Behavioral discrimination between quinine and KCl is dependent on input from the seventh cranial nerve:
implications for the functional roles of the gustatory nerves in rats. J. Neurosci., 18: 4353-4362.
28. Hanamori, T., I.J. Miller, and D.V. Smith, 1988. Gustatory Responsiveness of Fibers in the Hamster Glossopharyngeal Nerve. Journal of Neurophysiology, 60: 478-498.
29. Frank, M.E. and G.H. Nowlis, 1989. Learned Aversions and Taste Qualities in Hamsters. Chemical Senses, 14: 379-394.
30. Harada, S. and D.V. Smith, 1992. Gustatory Sensibilities of the Hamster's Soft Palate. Chem. Senses, 17: 37-51.
31. Travers, J.B., S.P. Travers, and R. Norgren, 1987. Gustatory Neural Processing in the Hindbrain. Ann. Rev. Neurosci., 10: 595-632.
32. Travers, S.P., 1993. Chapter 13: Orosensory Processing in neural Systems of the Nucleus of the Solitary Tract, in Mechanisms of Taste Transduction, S.A. Simon and S.D. Roper, Editor. CRC Press: Boca Raton. 339-394.
33. Lindemann, B., 1997. Sodium Taste. Current Opinion in Nephrology and Hypertension, 6(5): 425-429.
34. Lindemann, B., T.A. Gilbertson, and S.C. Kinnamon, 1999. Amiloride Sensitive Sodium Channels in Taste, in Amiloride Sensitive Sodium Channels: Physiology and Functional Diversity, D.J. Benos, Editor. Academic Press: San Diego. in press.
35. Ninomiya, Y. and A. Funakoshi, 1982. Responsiveness of Dog Thalamic Neurons to Taste Stimulation of Various Tongue Regions. Physiol. Behav., 29: 741-745.
36. Garvin, J.L., R. Robb, and S.A. Simon, 1988. Spatial Map of Salts and Saccharides on Dog Tongue. Am. J. Physiol., 255: R117 - R122.
37. Sato, T., M. Ohkusa, Y. Okada, and M. Sasaki, 1983. Topographical difference in taste organ density and its sensitivity of frog tongue. Comp. Biochem. Physiol., 76A: 233 - 239.
38. Stevens, S.S., 1969. Sensory scales of taste intensity. Percept. Psychophys., 6: 302-308.
39. Stevens, J.C., 1971. Psychophysical problems and procedures, in Stimulus and Sensation, W.S. Cain and L.E. Marks, Editor. Little Brown: Boston, MA. 5-18.
40. McBurney, D.H., 1978. Psychological Dimensions and Perceptual Analyses of Taste, in Handbook of Perception VI(A): Tasting and Smelling, E.C. Carterette and M.P. Friedman, Editor. Academic: New YOrk. 125-156.
41. Baird, J. and E. Noma, 1978. Fundamentals of Scaling and Psychophysics. New YOrk: Wiley. 287.
42. Lawless, H.T., 1987. Chapter 17: Gustatory Psychophysics, in Neurobiology of Taste and Smell, T.E. Finger and W.L. Silver, Editor. Wiley Interscience: New York. 401-420.