Maturational Changes in the Human Envelope-following Responses

Abstract

IntroductionThe auditory ability to discriminate rapid changes in the envelope of language sounds is essential for speech comprehension. Human envelope-following responses (EFRs) are useful for objective measurement of temporal auditory processing in subjects who are unable to give accurate behavioural responses (e.g., young children). ObjectiveTo evaluate age-dependent changes in EFRs during the first 2 years of life. MethodsThe EFRs were recorded in a sample of 16 healthy babies distributed into 2 age groups (G1: 12 newborns; G2: 4 babies of 2 years). The EFRs were evoked by white noise carrier stimuli with a sweep of modulation frequencies from 20 to 200Hz presented at 50dB HL. ResultsThe age-related changes affected both morphology and EFR detectability. The main morphological differences were at the expense of frequencies below 50Hz, where the first component P1 was not well defined in either of the 2 age groups. For all modulation frequencies, age significantly affected EFR amplitude and detectability. ConclusionsThe present study provides the first evidence on EFR maturation. Some understanding of normal EFR development would facilitate a better use of this technique in clinically objective measurement of auditory temporal processing in infants who cannot provide reliable behavioural responses.