N400 and short speech stimuli.

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.

Recognition and production of emotions in children with cochlear implants.

The aim of this study was to examine auditory recognition and vocal production of emotions in three prelingually bilaterally profoundly deaf children aged 6-7 who received cochlear implants before age 2, and compare them with age-matched normally hearing children. No consistent advantage was found for the normally hearing participants. In both groups, sadness was recognized best and disgust was the most difficult. Confusion matrices among other emotions (anger, happiness, and fear) showed that children with and without hearing impairment may rely on different cues. Both groups of children showed that perception is superior to production. Normally hearing children were more successful in the production of sadness, happiness, and fear, but not anger or disgust. The data set is too small to draw any definite conclusions, but it seems that a combination of early implantation and regular auditory-oral-based therapy enables children with cochlear implants to process and produce emotional content comparable with children with normal hearing.

Cortical auditory evoked potentials in unsuccessful cochlear implant users.

In some cochlear implant users, success is not achieved in spite of optimal clinical factors (including age at implantation, duration of rehabilitation and post-implant hearing level), which may be attributed to disorders at higher levels of the auditory pathway. We used cortical auditory evoked potentials to investigate the ability to perceive and discriminate auditory stimuli in 10 unsuccessful implant users aged 8-10 years (CI) and 10 healthy age-matched controls with normal hearing (NH). Pure tones (1 and 2 kHz) and double consonant-vowel syllables were applied. The stimuli were presented in an oddball paradigm that required the subjects to react consciously. The latencies and amplitudes of the P1, N1, P2, N2 and P3 waves were analyzed, in addition to reaction times and number of responses. Significant differences in the average response times and number of responses were observed between the CI and NH groups. The latencies also indicate that the CI group took longer to perceive and discriminate between tonal and speech auditory stimuli than the NH group.

Electropalatographic specification of Croatian fricatives /s/ and /z/.

Electropalatographic specification of alveolar fricatives in Croatian is aimed at providing speech therapists with normative data about the range of acceptable productions of /s/ and /z/ in adult speakers of Croatian. Four variables were analysed: place of articulation, total contact, groove width and hold phase duration. Intra- and inter-speaker variability for each variable was analysed. Lingual palatal cues for voicing difference were also quantified and discussed. Results show that Croatian /s/ and /z/ are alveolar and not dental as previously reported. The comparison between the voiced and the voiceless fricative shows that durational measures provide the best differentiation. The voiceless counterpart is significantly longer. The difference between voiced and voiceless is also found in the total contact, with /z/ having more contact in the anterior four rows of electrodes, while /s/ has more contact in the posterior four rows of electrodes. This difference is also reflected in the anterior and the posterior groove widths. Possibilities of using these results as normative data for the diagnosis and treatment of atypical articulation of /s/ and /z/ are discussed.

Acquisition of /s/ clusters in Croatian speaking children with phonological disorders.

The authors studied the acquisition of nine #sC clusters in 30 Croatian-speaking phonologically disordered children, aged between 3;8-7;0 years, by analysing their renditions of target words elicited in response to visual stimuli presented on a computer screen. Results did not support the idea that a greater jump in sonority from C1 to C2 would translate into a greater accuracy of productions. The percentage of correct realizations was high for /s/+nasal combinations (mean 85%), and for approximants /j/ and // (mean 77%) and stops (mean 73%), with significantly lower scores for liquids /l/ and /r/ (mean 47%). The difference between SSP-violating and SSP-following targets was not significant, and neither was the homorganicity of the target. The most frequent errors were substitution of the first consonant (i.e. /s/) while keeping the second one. These children are significantly different from the typically-developing group in two ways. First, retention of the first or the second consonant is not as frequent, and, second, /l/ is almost as difficult as /r/, as opposed to the typically-developing children who had no more difficulty with /l/ than with the other two approximants. Although cluster reduction is not the most common process in erroneous productions, the patterns emerged here generally agree with the findings from other languages.

Fricatives, affricates, and vowels in Croatian children with cochlear implants.

The aim of the research was to analyse the speech of children with cochlear implants over approximately a 46-month period, and compare it with the speech of hearing controls. It focused on three categories of sounds in Croatian: vowels (F1 and F2 of /i/, /e/, /a/, /o/ and /u/), fricatives /s/ and /integral/ (spectral differences expressed in terms of center of gravity), and affricates /ts/ and /t integral/ (accuracy, total duration, and pattern of stop-fricative components). One group of subjects were 10 implanted children who had been profoundly deaf before implantation. There were four recordings per child. Group two children were hearing controls matched for age and sex. The results show that the implanted children are closest to unimpaired children in terms of their formant-defined vowel space. Their fricatives exhibit poor distinction in terms of the noise spectrum, and the affricates are the most difficult to produce.

Acoustic analysis of the speech of children with cochlear implants: a longitudinal study.

The aim of the study was to analyse the speech of the children with cochlear implants, and compare it with the speech of hearing controls. We focused on three categories of Croatian sounds: vowels (F1 and F2 frequencies), fricatives (noise frequencies of /s/ and /S/ ), and affricates (total duration and the pattern of stop-fricative components in /ts/ and /tS/ ). Eighteen implanted children, aged between 9;5 and 15;2 years participated in the study. All had been profoundly hearing impaired before implantation. Three recordings per child were made over a 20-month period. The hearing controls were matched for age and sex. Implanted children had a smaller and fronted vowel space, their /s/ and /S/ noise frequencies overlapped, affricates were longer, with a high proportion of incorrect productions and substitutions. With time, there was a small but steady overall improvement in all categories. Early intervention (rehabilitation and implantation) are crucial for good speech acquisition.

Speech perception of children with cochlear implants and children with traditional hearing aids.

The aim of the study was to analyse speech perception of children with cochlear implants (N = 29) and children fitted with traditional hearing aids (N = 20). One- and two-syllable words were presented auditorily in a forced choice minimal-pair discrimination task. The children repeated the word and pointed to the appropriate picture presented on computer screen. The words were minimal pairs with respect to voicing or place of articulation in stops and fricatives; among affricates the minimal pairs included the most frequently substituted fricatives and stops in addition to voicing and place of articulation. Vowel discrimination was tested in minimal pairs and in nonsense words differing only in the vowel. Unaided, all children were profoundly hearing impaired and were included in auditory-oral therapy (Verbotonal method). The smallest differences between the groups were found for stops and vowels, and the largest for fricatives and affricates. The implanted children were significantly more successful.

The relationship between active hand and ear advantage in the native and foreign language.

In an experimental design involving two auditorily presented competing commands (one to each ear), 144 right-handed subjects (72 male and 72 female) were asked to provide motor responses. Half of each group of subjects was responding with their right hand and the other half with the left. The test was applied in the subjects' native language (Croatian) and in English, which they had learned as a foreign language. Ear advantage was determined by calculating laterality indices from the order of responding to the commands. On average, right-ear advantage was found in all conditions. Analysis of results revealed the effect of the active hand in Croatian (with significant decrease in the right-ear advantage when using the left hand). The same trend failed to reach significance in English. In responses to English stimuli, there was a significant effect of gender (with men exhibiting a lower right-ear advantage than women). The same trend was not significant for Croatian stimuli. The consistently lower right-ear advantage found in male subjects is contrary to the traditional assumptions that men are more lateralized than women and warrants further investigation.

Hemispheric asymmetry for linguistic prosody: a study of stress perception in Croatian.

The aim of the study was to test for possible functional cerebral asymmetry in processing one segment of linguistic prosody, namely word stress, in Croatian. The test material consisted of eight tokens of the word pas under a falling accent, varying only in vowel duration between 119 and 185 ms, attached to the end of a frame sentence. The sentence could, depending on the duration of the vowel, mean 'This is a beautiful dog' or 'This is a beautiful belt/waist.' Each sentence was presented eight times in three dichotic listening conditions (binaural, left ear only, right ear only), in random order. Fourty healthy female right-handers participated in a forced-choice lexical task. For each presented sentence they had to decide whether it referred to the animal (short vowel in the key word) or to the belt/waist (long vowel in the key word). Their oral responses were analyzed in terms of response time and categoricity. No consistent significant differences were found among listening conditions. The responses possibly reflect the nonlateralized activity of subcortical regions or a simultaneous activity of both hemispheres relying on different cues.

Languages in space.

The activation-orienting hypothesis and possible effects of hemispace for verbal stimuli in the native (Croatian) and foreign (English) language were studied on a sample of 72 healthy female right-handers. In an experimental design involving two competing commands referring to objects in left and right hemispace presented simultaneously to the two ears it was recorded which of the two was attended to first. The activation-orienting hypothesis was confirmed for Croatian but not for English. Clear dissociation between the two languages was found with respect to preferred hemispace: for the stimuli in the native language the subjects preferred the left hemispace, whereas for the stimuli in the foreign language they preferred the right hemispace.