N400 and short speech stimuli

ABSTRACT

In some children who have cochlear implants (CI), the expected speech-language outcome is not achieved despite fulfilment of requirements for its successful use. This may be attributed to processing difficulties at higher levels of the auditory pathway. The aim of this study was to investigate the processing of speech stimuli at the auditory-cortex level in 20 children aged 8 to 10 years who have a hearing impairment and have been using cochlear implants, by means of cortical auditory evoked potentials (CAEP). The children were divided into two groups, depending on the outcome: 10 successful implant users and 10 unsuccessful implant users, whose speech-language development has not progressed as expected. The control group comprised of 10 age-matched children with typical hearing and speech-language development. Two double consonant+vowel syllables (CVCV) were used as stimuli, presented in an oddball paradigm that required the subjects to react consciously. Latencies and amplitudes of CAEP waves were measured. In addition to the waves that typically occur in CAEP and reflect auditory processing at the level of the auditory cortex, N400 wave (associated with semantic processing) was recorded in the normally hearing group and successful CI users, but not in the unsuccessful CI users. Additionally, successful CI users and controls had comparable latencies of the P300 wave (preceding the N400) as well. Although P300 and N400 reflect two processes, they are related so that if P300 does not reach the expected amplitude and latency, neither will N400.

KEYWORDS:

• Cochlear implant
• cortical auditory evoked potentials (CAEP)
• children
• N400
• speech stimulus

Acknowledgments

This work was supported by Croatian Science Foundation under grant IP-2016-06- 5367 and by the University of Zagreb, Faculty of Humanities and Social Sciences. The authors wish to thank the children and their parents for participation. Constructive suggestions of the reviewers are gratefully acknowledged.

Disclosure Statement

The authors report no conflict of interest.

Additional information

Funding

This work was supported by the University of Zagreb, Faculty of Humanities and Social Sciences;Croatian Science Foundation [IP-2016-06- 5367].