The envelope following response: scalp potentials elicited in the Mongolian gerbil using sinusoidally AM acoustic signals.

Scalp potentials which follow the low frequency envelope of a sinusoidally amplitude modulated stimulus waveform were evoked and recorded in anesthetized gerbils. This envelope following response (EFR) is presumably due to the synchronized discharge of populations of neurons in the auditory pathway. The magnitude of the EFR increased and the latency decreased in a near monotonic fashion with increased stimulus intensity and modulation depth. The modulation rate transfer function (MRTF) was determined for modulation frequencies between 10 and 920 Hz imposed on carrier frequencies ranging from 1 to 7 kHz. The MRTF was low pass in character having a corner frequency of 100-120 Hz. Measurements of the group delay, determined from the phase of the response relative to the stimulus phase, indicate that the response is generated in at least three distinct regions within the auditory pathway.