The frequency selectivity of information-processing channels in the tactile sensory system

The frequency selectivity of the P, NP I, and NP II channels of the four-ch annel model of mechanoreception for glabrous skin was measured psychophysic ally by an adaptation tuning curve procedure. The results substantially ext end the frequency range over which the frequency selectivity of these chann els is known and further confirm the hypothesis that the input stage of eac h of these channels consists of specific sensory nerve fibers and associate d receptors. Specifically, the frequency characteristics of Pacinian nerve fibers, rapidly adapting (RA) nerve fibers, and slowly adapting Type II (SA II) nerve fibers were found to be the peripheral neurophysiological correl ates of the P, NP I, and NP II channels, respectively. The finding that the tuning characteristic for a test stimulus of 250 Hz delivered through a sm all (0.008 cm(2)) contactor depended dramatically on the duration of the te st stimulus whereas the detection threshold did not, provides new evidence in support of the hypothesis that separate NP II and P channels exist.