THE ENVELOPE FOLLOWING RESPONSE TO MULTIPLE TONE PAIR STIMULI

The envelope following response (EFR) is a steady-state evoked respons e which follows the envelope of a stimulating waveform. A tone pair wi th frequencies f(1) and f(2) generates a temporal envelope whose perio d corresponds to the difference in frequency between the constituent t ones (f(2)-f(1)=f(2,1)). EFRs were recorded from Mongolian gerbils usi ng amplitude-modulated stimuli comprised of from 1 to 4 tone pairs. Fi ve stimulus tone pairs were used having center frequencies of approxim ately 0.3, 1, 2, 3, and 5 kKz; their corresponding envelope frequencie s were approximately 38, 55, 66, 85, and 142 Hz. The magnitude of the EFR to each tone pair was measured separately and in combination with other simultaneously presented tone pairs. Small decreases (1-3 dB) in response magnitude, relative to the single tone pair condition, resul ted from the addition of 1-2 tone pairs of higher frequencies; this ef fect was more pronounced with the addition of a third and fourth tone pair. However, the addition of the 300 Hz tone pair resulted in the si gnificant enhancement of the response to higher frequency tone pairs. These data indicate that multiple tone pair EFRs may be a useful techn ique for the rapid acquisition of frequency-specific audiometric infor mation.