Sharpness of touch

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The acuity of touch - also fine perception or epicritical sensitivity - is the ability to perceive spatially closely adjacent touch stimuli as separate stimuli and thus part of tactile perception .

The tactile acuity can be determined as a measure for a differential perceptibility threshold, for example with the two-point discrimination threshold. This measures the ability to differentiate between two point stimuli that exceed the stimulus threshold of the sense of touch but are well below the threshold of protopathic sensitivity , for example on the fingertip . The test subjects touch two needle tips that are at different distances. The distinction threshold is reached when the two needle tips can no longer be perceived separately. The corresponding needle distance is then a measure of the tactile acuity. A distinction is made between the simultaneous and the successive two-point discrimination threshold. With the first, the needles are attached simultaneously and with the second, one after the other. The successive two-point discrimination threshold is up to four times more sensitive than the simultaneous one. Simultaneously is usually used because it is easier to implement.

Young people and especially blind people who are trained to feel Braille (such as Braille ) have a tactile acuity of around 1.5 millimeters on the fingertips, while older people often only up to four millimeters. The sharpness of touch can be maintained or partially even improved through regular use of the sense of touch, for example when working or playing a musical instrument . Also, electrical stimulation responsible for the sense of touch nerves can improve Tastschärfe.

The acuity of touch of different skin regions varies greatly. Low values ​​(less than one centimeter) are especially reached on the tongue, lips and fingers. The threshold is largest on the legs and back and is several centimeters (approximately seven centimeters).

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Individual evidence

  1. ↑ Tactile system - knowledge for medical professionals. Retrieved December 19, 2019 .
  2. ↑ Niels Birbaumer, Robert F. Schmidt: Biological Psychology. [Bonus material on the web], 6th edition, Heidelberg. Springer Medicine, 2006, ISBN 3-540-25460-9 .