Normal childhood development of the auditory systems involves mapping sounds to meaning and the neural coding of speech. Children are often subjected to adverse listening environments such as high levels of background noise. This paper aimed to delineate the effects of background noise on the speech-evoked frequency following response (FFR), which provides a snapshot of auditory processing. They assessed the auditory-physiological responses to a consonant-vowel sound syllable [da] in 58 normally developing 3-5 year olds in two environments: quiet and background noise (6-talker babble). Results showed that responses were degraded in noise: they were smaller and slower. They were an average of 0.3ms slower in noise than in quiet. Responses to the vowel sound were greater than the consonant, across both noise and quiet environments. Responses in quiet were more stable on a trial-by-trial basis than those in noise. The degradations in noise were more pronounced for the consonant than the vowel, demonstrating particular vulnerability in processing these speech sounds in noise. This is consistent with other studies showing that the properties of consonants make them more susceptible to masking and thus more difficult than vowels to recognise in noisy environments. Before we are able to understand auditory processing disorders and their neurophysiological correlates in early childhood, it is necessary to develop an understanding of the neurophysiology of speech processing in normally developing pre-schoolers.
This paper goes some way to provide an objective profile for auditory-neurophysiological speech processing in pre-school children, which may be useful when evaluating children for auditory processing difficulties.
This cohort will be followed up and I am interested to see how these evoked potentials may relate to their future listening and literacy skills.
