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. 1981 Jan;310:117–144. doi: 10.1113/jphysiol.1981.sp013540

Neural mechanisms of spatial tactile discrimination: neural patterns evoked by braille-like dot patterns in the monkey.

K O Johnson, G D Lamb
PMCID: PMC1274731  PMID: 7230030

Abstract

1. The experiments reported here were designed to investigate the responses of cutaneous mechanoreceptive afferents to spatially configured dot patterns scanned across the skin. Braille-like patterns were selected because the discrimination of Braille characters must depend on spatial patterning rather than some other facet of the afferent discharge. 2. A multifactorial experimental design was used in which each afferent fibre was studied using every combination of six dot patterns, two dot sizes, two dot spacings, two contact forces and two scanning velocities. Two other factors, scanning direction relative to the skin ridges and intermittent versus continuous scanning, were studied. 3. Beside the general question concerning the response properties of the mechanoreceptive afferents, three major questions were addressed here. (i) What is the critical spatial dimension at which neural spatial patterning breaks down and below which tactual discrimination must depend on facets of the afferent discharge other than spatial neural patterning? (ii) Which mechanoreceptive population sets this critical dimension? (iii) Why is tactual discrimination enhanced by lateral scanning? 4. The results presented here suggest that the critical dimension, below which spatial neural patterning breaks down, is of the order of 1.0 mm and that the slowly adapting (SA) afferent fibres are responsible for this limit. 5. At dimensions above approximately 1.0 mm the spatial contrast between peaks and troughs in the SA discharge is markedly enhanced during scanning. When the skin is stationary the discharge rates in the SA population drop rapidly to low levels. A second possible reason for enhanced tactual discrimination during scanning is related to the increased spatiotemporal information in a coherent pattern of neural activity moving across a discrete population of afferent fibres. 6. The effects of variations in conduction velocity are analysed and it is shown that they place serious constraints on the transmission of spatiotemporal information.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. CAUNA N., MANNAN G. The structure of human digital pacinian corpuscles (corpus cula lamellosa) and its functional significance. J Anat. 1958 Jan;92(1):1–20. [PMC free article] [PubMed] [Google Scholar]
  2. Chambers M. R., Iggo A. Slowly-adapting cutaneous mechanoreceptors. J Physiol. 1967 Sep;192(2):26P–27P. [PMC free article] [PubMed] [Google Scholar]
  3. Darian-Smith I., Davidson I., Johnson K. O. Peripheral neural representation of spatial dimensions of a textured surface moving across the monkey's finger pad. J Physiol. 1980 Dec;309:135–146. doi: 10.1113/jphysiol.1980.sp013499. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Darian-Smith I., Johnson K. O., Dykes R. "Cold" fiber population innervating palmar and digital skin of the monkey: responses to cooling pulses. J Neurophysiol. 1973 Mar;36(2):325–346. doi: 10.1152/jn.1973.36.2.325. [DOI] [PubMed] [Google Scholar]
  5. Darian-Smith I., Kenins P. Innervation density of mechanoreceptive fibres supplying glabrous skin of the monkey's index finger. J Physiol. 1980 Dec;309:147–155. doi: 10.1113/jphysiol.1980.sp013500. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. GIBSON J. J. Observations on active touch. Psychol Rev. 1962 Nov;69:477–491. doi: 10.1037/h0046962. [DOI] [PubMed] [Google Scholar]
  7. Grunwald A. P. A braille-reading machine. Science. 1966 Oct 7;154(3745):144–146. doi: 10.1126/science.154.3745.144. [DOI] [PubMed] [Google Scholar]
  8. Harrington T., Merzenich M. M. Neural coding in the sense of touch: human sensations of skin indentation compared with the responses of slowly adapting mechanoreceptive afferents innvervating the hairy skin of monkeys. Exp Brain Res. 1970;10(3):251–264. doi: 10.1007/BF00235049. [DOI] [PubMed] [Google Scholar]
  9. Johansson R. S., Vallbo A. B. Tactile sensibility in the human hand: relative and absolute densities of four types of mechanoreceptive units in glabrous skin. J Physiol. 1979 Jan;286:283–300. doi: 10.1113/jphysiol.1979.sp012619. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Johnson K. O., Darian-Smith I., LaMotte C. Peripheral neural determinants of temperature discrimination in man: a correlative study of responses to cooling skin. J Neurophysiol. 1973 Mar;36(2):347–370. doi: 10.1152/jn.1973.36.2.347. [DOI] [PubMed] [Google Scholar]
  11. Johnson K. O. Reconstruction of population response to a vibratory stimulus in quickly adapting mechanoreceptive afferent fiber population innervating glabrous skin of the monkey. J Neurophysiol. 1974 Jan;37(1):48–72. doi: 10.1152/jn.1974.37.1.48. [DOI] [PubMed] [Google Scholar]
  12. Knibestöl M. Stimulus-response functions of rapidly adapting mechanoreceptors in human glabrous skin area. J Physiol. 1973 Aug;232(3):427–452. doi: 10.1113/jphysiol.1973.sp010279. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Knibestöl M. Stimulus-response functions of slowly adapting mechanoreceptors in the human glabrous skin area. J Physiol. 1975 Feb;245(1):63–80. doi: 10.1113/jphysiol.1975.sp010835. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Talbot W. H., Darian-Smith I., Kornhuber H. H., Mountcastle V. B. The sense of flutter-vibration: comparison of the human capacity with response patterns of mechanoreceptive afferents from the monkey hand. J Neurophysiol. 1968 Mar;31(2):301–334. doi: 10.1152/jn.1968.31.2.301. [DOI] [PubMed] [Google Scholar]

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