Electrophysiological Characterisation of Envelope-Following Responses ☆

Abstract Introduction The auditory ability to discriminate rapid changes in the envelope of language sounds is essential for speech comprehension. This ability is deteriorated in some neurological diseases such as multiple sclerosis, auditory neuropathy, sensorineural hearing loss, presbycusis, and primary developmental language disorder. Envelope-following responses (EFRs) in humans are useful in objective measurement of temporal processing in the auditory nervous system. Objectives To evaluate EFRs in healthy younger subjects and to investigate the effects of subject states on the EFRs recorded. Methods Eleven young subjects were included; 6 of them were awake and 5 were asleep. EFRs were evoked by white noise carrier stimuli with a sweep of modulation frequencies from 20 to 200 Hz presented at 50 dB HL. Results The EFRs we recorded were similar in all subjects. There were two principal components. During both subject sleep and wakefulness, the first component (located between 30 and 50 Hz) was significantly larger than the second component (located between 80 and 110 Hz). There was also a significant effect of sleep on the EFR amplitude for the modulation frequencies between 88 and 110 Hz, 155 and 165 Hz, and 190 and 200 Hz. However, there were no significant effects of sleep on the principal EFR components. Conclusions These results corroborate the usefulness of the EFR technique for objective measurement of human auditory temporal processing.