Deficit of long-term memory traces for words in children with cochlear implants

Abstract

Objective: Language experience can develop long-term memory traces for speech units in the brain, to ensure efficient processing of speech sounds. However, prelingually deafened children lack sufficient auditory input before cochlear implantation. Whether the experience-dependent long-term memory traces exist in prelingually deafened children with cochlear implants (CIs) remains unclear.

Methods: We presented CI and normal hearing (NH) children with Mandarin Chinese spoken disyllables in an oddball paradigm and recorded event-related potentials. Each disyllable was defined as a meaningful word or a meaningless pseudoword by the tonal information in the second syllable.

Results: The amplitude of mismatch negativity (MMN) elicited by words was larger than that elicited by pseudowords in NH children. However, this enhancement of the MMN amplitude was not found in CI children. Behavioral results showed later recognition points for words and lower accuracies for speech comprehension in CI children than in NH children. Furthermore, increased theta power for words compared with pseudowords was only found in NH children.

Conclusions: Our findings indicate a deficit of long-term memory traces for words in prelingually deafened children with cochlear implants.

Significance: Early speech input may be crucial to the formation of long-term memory traces for speech units.

Keywords: Cochlear implant; Disyllabic word; Long-term memory trace; Mismatch negativity; Pseudoword.