Frequency-following response evoked by acoustic stimuli in normal and profoundly deaf subjects.

A low-frequency acoustic stimulus was applied to the right mastoid, the right acromion and the distal phalanx of the right index finger in 10 healthy and 10 profoundly deaf subjects. The stimulus, which had a frequency of 80-120 Hz, was delivered by means of a special vibrating system, constructed for this purpose. The frequency-following response (FFR) was recorded. In all the healthy subjects, FFR appeared with a latency of about 6 ms from the stimulus onset and with a peak-to-peak amplitude of 0.3-1.2 microV. Also, in all the deaf subjects, a change in bioelectrical activity was recorded, which reproduced the stimulus frequency at a latency of about 6 ms and with a peak-to-peak amplitude of 0.3-1.2 microV. Afferent pathways by which the stimulus could be transmitted in deaf subjects are discussed.