The Perception of Stress Pattern in Young Cochlear Implanted Children: An EEG Study

Abstract

Children with sensorineural hearing loss may (re)gain hearing with a cochlear implant—a device that transforms sounds into electric pulses and bypasses the dysfunctioning inner ear by stimulating the auditory nerve directly with an electrode array. Many implanted children master the acquisition of spoken language successfully, yet we still have little knowledge of the actual input they receive with the implant and specifically which language sensitive cues they hear. This would be important however, both for understanding the flexibility of the auditory system when presented with stimuli after a (life-) long phase of deprivation and for planning therapeutic intervention. In rhythmic languages the general stress pattern conveys important information about word boundaries. Infant language acquisition relies on such cues and can be severely hampered when this information is missing, as seen for dyslexic children and children with specific language impairment. Here we ask whether children with a cochlear implant perceive differences in stress patterns during their language acquisition phase and if they do, whether it is present directly following implant stimulation or if and how much time is needed for the auditory system to adapt to the new sensory modality. We performed a longitudinal ERP study, testing in bimonthly intervals the stress pattern perception of 17 young hearing impaired children (age range: 9–50 months; mean: 22 months) during their first 6 months of implant use. An additional session before the implantation served as control baseline. During a session they passively listened to an oddball paradigm featuring the disyllable “baba,” which was stressed either on the first or second syllable (trochaic vs. iambic stress pattern). A group of age-matched normal hearing children participated as controls. Our results show, that within the first 6 months of implant use the implanted children develop a negative mismatch response for iambic but not for trochaic deviants, thus showing the same result as the normal hearing controls. Even congenitally deaf children show the same developing pattern. We therefore conclude (a) that young implanted children have early access to stress pattern information and (b) that they develop ERP responses similar to those of normal hearing children.

The MMN as a viable and objective marker of auditory development in CI users

“…In the context of electrophysiological measures in cochlear implantation, this is particularly relevant since one of the main objectives is the possibility to differentiate auditory vs. non-auditory influences on the outcomes. Importantly, as opposed to prelingually implanted children, in postlingually deafened CI-users, the auditory development has been shaped by prior hearing experience, helping them to process auditory information from the CI (Vavatzanidis et al, 2015;Torppa et al, 2012;Petersen et al, 2012;Caposecco et al, 2012). Thus, the limitations of CIs can be particularly critical for congenitally deaf children with CIs.…”

“…With the exception of a few studies (Vavatzanidis et al, 2015;Torppa et al, 2012Torppa et al, , 2014b, all MMN studies on CI children reviewed here involve older children or adolescents with a prolonged period (more than 3e5 years) of deafness (Table 1). The current practice, however, is to implant the children at around 1 year of age which may further promote their language skills (for a review see Vlastarakos et al, 2010).…”

“…An important aspect of children's perception of speech is the perception of word stress and their patterns which convey information about word boundaries in rhythmic languages like German, English, French, Hebrew (for a review, Vavatzanidis et al, 2016) and Finnish (word stress perception in Finnish CI children, see Torppa et al, 2014a). Using this cue, young children are able to derive Top: Grand-average (five CI users) event-related potentials (ERP) difference waves at the frontal scalp site (Fz) to frequency changes (ERPs to standard-frequency tones subtracted from the ERPs to deviant-frequency tones) for the different frequency ranges 1 year and 2.5 years after CI activation.…”

“…The acoustic cues for word stress are changes in pitch (f 0 ), intensity and duration (for a review, Torppa et al, 2014a). Vavatzanidis et al (2015) followed the development of the MMN for vowel duration (length) right after the implantation in young CI children (age at CI activation from 11 to 45 months) and in the NH control group. In their MMN paradigm,/ba/was presented either with a short or with lengthened vowel.…”

“…(p. 2437). Vavatzanidis et al (2016) followed the development of the MMN for changes in syllable stress patterns in CI children (age at first activation of the CI, 9e50 months) during first six months after CI activation and in the NH control group. In one of the two stimulus blocks, the trochaic pattern (the first syllable stressed, e. g.,/ba:ba/) was the standard stimulus and the iambic pattern (the second syllable stressed, e. g.,/baba:/) the deviant stimulus or vice versa.…”