Individual magnitude estimation functions and their relation to the Pacinian (P) and non-Pacinian (NP) channels

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Abstract
Four distinct channels of information can combine to signal the sensation magnitude of tactile stimuli. For example, a 250‐Hz vibratory stimulus of large size (2.9 cm2) and of low/moderate intensities activates the P channel, but at higher intensities the NP channels also are activated. Because of saturation and the potentially different functional properties of the various channels, crossing from one channel (e.g., P) to another (e.g. NP II) along the intensity domain may result in breaks in the overall sensation magnitude functions. Absolute magnitude estimation (AME) experiments were performed on six observers [250 Hz and narrow‐band noise (175–350 Hz), 700‐ms duration, 500‐ms rise/fall time, thenar eminence, 2.9‐cm2 contactor size; 15, 30, 40 °C skin surface temperature]. Results of individual observers were of particular interest since averaging across observers can obscure breaks due to idiosyncratic differences in their location. As previously shown, the averaged AME functions approximated power law relationships. The individual functions, however, were scalloped in shape with breaks that coincided with the individual P/NP II crossovers. Other breaks occurring at SL levels below the NP II threshold may be explained by the manner in which P corpuscle fibers entrain to vibratory stimuli and how this entrainment is disrupted by noise. [Work supported by NIH Grant Nos. DC00380 and DC00098.]

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