Neuronal coding by cortical cells of the frequency of oscillating peripheral stimuli.

One class of neurons in the somatic sensory cortex of unanesthetized monkeys is rhythmically entrained by sinusoidal mechanical stimulation of the skin of the hand at low frequencies. A second class, which is linked to Pacinian afferents, increases its rate of discharge in response to high-frequency peripheral stimuli but is not entrained. The vibratory sense is served by two distinct classes of cortical cells. The code for the group sensitive to low-frequency stimuli is the temporal order of impulses; for the high-frequency group the code is the labeled line.