Journal of Neuroscience, Vol 4, 2016-2024, Copyright © 1984 by Society for Neuroscience
The neural signal for the intensity of a tactile stimulus
DA Poulos, J Mei, KW Horch, RP Tuckett, JY Wei, MC Cornwall and PR Burgess
The effect of indenting the skin at different rates on the perceived
intensity of the stimulus was studied by indenting the skin of the
fingertip with two triangular waveforms, given as a pair. The subjects were
asked to judge which member of the pair was more intense. Perceived
intensity was found to increase both with the depth and the speed of the
indentation. In contrast, changes in the rate of skin indentation had
little influence on perceived skin indentation depth. This suggests that
intensity and depth are different attributes of tactile sensibility. Since
the skin is viscous, a rapid indentation is more forceful than a slow
indentation of the same depth, raising the possibility that perceived
intensity is related to stimulus force. Even though intensity judgments
were more closely correlated with the force of a stimulus than with the
indentation it produced, a rapidly increasing force was felt as more
intense than one that increased more slowly but attained the same final
magnitude. When mechanoreceptors in the palmar aspect of the monkey's hand
were excited with triangular stimuli like those used in the psychophysical
studies, their discharge frequency increased with the rate of skin
indentation. However, the receptors were distinctly more rate sensitive
than the human judgments of stimulus intensity, suggesting that impulse
summation in the central nervous system summates (integrates in the
mathematical sense) the receptor input so as to enhance, relatively, the
perceived intensity of the slower stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
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