The relationship between speech in noise perception and auditory working memory capacity in monolingual and bilingual adults.

OBJECTIVE: Speech-in-noise perception is dependent on the interaction between sensory and cognitive processes. One factor that can relate to both processes is bilingualism. This study aimed to determine the correlation between auditory-working-memory and speech-in-noise in Persian monolinguals and Kurdish-Persian bilinguals. DESIGN: Speech-in-noise tests (sentences-in-noise and syllables-in-noise) and auditory-working-memory tests (forward and backward digit span, and n-back) were performed. STUDY SAMPLE: Participants were 48 Kurdish-Persian bilinguals with a mean age of 24 (±4) years and 48 Persian monolinguals with a mean age of 25 (±2) years with normal hearing. RESULTS: Both language groups scored within normal limits in all memory and speech-in-noise tests. However, bilinguals performed significantly worse than monolinguals on all auditory-working-memory tests and the sentences-in-noise test. Monolinguals outperformed bilinguals in sentences-in-noise test (∼1.5 dB difference) and all auditory-working-memory tests (∼1 digit difference). The two groups did not significantly differ in syllables-in-noise test. Both groups had a significant correlation between working memory capacity and sentences-in-noise test. However, no significant correlation was found between syllables-in-noise and working memory capacity at any SNR. CONCLUSIONS: Cognitive factors such as auditory working memory appear to correlate with speech-in-noise perception ability (at least at the sentence level) in monolingual and bilinguals young adults.

The importance of working memory capacity for improving speech in noise comprehension in children with hearing aid.

BACKGROUND: One of the most common complaints of hearing aid users is difficulty in receiving speech in noise which is very important for all hearing impaired specially children with limited auditory and language experiences. Since working memory plays a significant role in speech perception, especially in challenging auditory situations such as background noise, it is likely that differences in its performance and capacity may impair the ability to understand speech in noise in hearing aid users. Therefore, we aimed to compare memory capacity between two groups of children using hearing aids in both ears, who differed only in the ability to understand speech in noise. METHODS: In this cross-sectional study, 31 children with moderate to severe hearing impairment and the same medical and demographical conditions that using bilateral hearing aids, were examined. These students were divided into two groups according to the scores obtained in speech comprehension as follows: group one (high performance) included students whose SNR loss score in BKB-Speech In Noise test was equal or less than 7, and group two (low performance) included students whose SNR loss score was more than 7. Then, the scores of auditory working memory tests were examined in these two groups. RESULTS: The scores of two working memory tests of forward and backward digit span between the two groups no differed significantly based on statistical findings (P = 0.06). But The score of working memory test of non-word repetition differed significantly between the two groups (P = 0.03) A significant correlation was found between the scores of speech comprehension in noise test and working memory tests, including forward (P = 0.004) and backward digit (P = 0.002) span tests and non-word repetition test (P = 0.000) in all subjects. CONCLUSION: The significant correlation founded between speech perception in noise scores and working memory span, indicating the importance of working memory capacity in the ability to understand speech in noise in children with hearing aids.

Speech-evoked auditory brainstem response; electrophysiological evidence of upper brainstem facilitative role on sound lateralization in noise.

BACKGROUND AND AIM: Sound lateralization/localization is one of the most important auditory processing abilities, which plays approved role in auditory streaming and speech perception in challenging situations like noisy places. In addition to the main role of lower brainstem centers like superior olivary complex in sound lateralization, efferent auditory system effects on improving auditory skills in everyday auditory challenging positions were revealed. This study evaluated noise effects on lateralization scores in correlation with an objective electrophysiologic test (Speech-ABR in noise), which objectively shows cumulative effects of the afferent and efferent auditory systems at the inferior colliculus and upper brainstem pathway. METHOD: Fourteen normal-hearing subjects in the age range of 18 to 25 participated in this study. Lateralization scores in the quiet and noisy modes were evaluated. Speech-ABR in both ears for quiet mode and three different contralateral noise levels (SNR = + 5, 0, - 5) were recorded, too. Correlation of lateralization scores and Speech-ABR changes in noise was studied. RESULTS: Significant decrease of lateralization scores with latency increase and amplitude decrease of Speech-ABR transient peaks (V, A, O) was seen with noise presentation. A high positive correlation between lateralization decrease with latency increase of onset peaks (V, A) and amplitude decrease of transient peaks (V, A, O) was found in low signal-to-noise ratios. CONCLUSION: The study revealed that in high challenging auditory situations like auditory lateralization in noise, upper brainstem centers and pathways play a facilitative role for main auditory lateralization centers in lower levels.

Speech-ABR in contralateral noise: A potential tool to evaluate rostral part of the auditory efferent system.

In parallel with the auditory afferent system, the auditory efferent system is active in all parts of the auditory pathways from auditory cortex to the cochlea. The auditory efferent system has two main segments: the rostral and the caudal parts. The rostral part, which starts from the cortical centers to thalamic nuclei and continues into collicular pathways in rostral brainstem, which sends its neural fibers to the main collicular nuclei especially inferior colliculus. The caudal part includes the olivocochlear bundle, which originates from the superior olivary complex and terminates on the cochlear hair cells. Most studies about the auditory efferent system have focused only on the caudal part using otoacoustic emission suppression test. Speech-evoked auditory brainstem response (S-ABR) as an electrophysiologic test that uses speech stimuli to simulate real-life auditory conditions, reflects the performance of rostral brainstem centers, so structurally seems to be an appropriate candidate to examine the rostral part of the auditory efferent system. Our hypothesis is that S-ABR in noisy condition, a typical condition for stimulating the auditory efferent system, has the potential to be used as an objective noninvasive electrophysiologic test for studying the rostral auditory efferent system in diagnosis and treatment/rehabilitation follow-ups. In addition, S-ABR can potentially reflect higher-order auditory functions and the effects of their dysfunctions on the lower brainstem. This characteristic makes S-ABR even more suitable tool for evaluation of the efferent system. To evaluate our hypothesis, Eighteen normal hearing subjects in the age range of 18-25 were tested in a pilot study for S-ABR in quiet mode and three signal to noise ratios of +10,0 and -10 for both ears. Then we checked the correlation between the results of S-ABR in different conditions and scores of auditory behavioral tests that auditory efferent system is involved in them: Consonant-Vowel perception in noise, dichotic Consonant-Vowel-Consonant and sound lateralization in noise. The results of our pilot study showed a significant correlation between S-ABR changes in noise with the scores of the behavioral tests in noisy or dichotic situations. Findings of the current study suggest that S-ABR with specific contralateral noise can be an appropriate option for evaluating the performance of rostral part of the auditory efferent system and may be suitable for top-down auditory training follow-ups, although the generalization of these results needs further studies in different groups with different auditory processing abnormalities or skills.

Effect of wireless remote microphone application on speech discrimination in noise in children with cochlear implants.

OBJECTIVES: Although cochlear implantation has significantly contributed to the speech perception of cochlear implant (CI) users, these individuals still have significant difficulty in understanding speech, especially in noisy environments and keeping track of the target speaker in the presence of speech sounds of others. This study was aimed to evaluate the effect of wireless Remote Microphones (RM) on speech discrimination scores in noise in child CI users. MATERIALS AND METHODS: Twenty children with unilateral cochlear implantation were enrolled in this study with mean ±â€¯SD age of 5.8 ±â€¯0.83 years who have undergone CI for at least one year. Speech discrimination scores in noise were assessed using the Words-in-Noise (WIN) test at a constant signal-to-noise ratio (SNR) of 0 dB, in the presence and absence of a wireless RM. Three loudspeakers were placed at a distance of 1 m in front of the child to present the speech and babble noise. The wireless microphone was placed on a base with a height equivalent to the height of the middle speech loudspeaker at a distance of 30 cm from it. FINDINGS: The mean speech discrimination score in noise in the absence of wireless RM in all children was obtained 34% (6.8 words out of 20 words), with minimum and maximum of 15% and 50% words. Findings revealed the mean speech discrimination score in noise in the presence of wireless RMs is equivalent to 65% (13 words out of 20 words), with the minimum and maximum scores of 35% and 95%, respectively. The result showed that speech discrimination scores in noise improved in the presence of wireless RM. CONCLUSION: The significant improvement was observed in speech discrimination in noise in all cochlear implanted children when the wireless RM was used, as compared to the absence of a wireless RM, which suggests the usefulness of this hearing aid accessory in CI users.