Sistema auditivo eferente: efeito no processamento auditivo

Effect of Contralateral Acoustic Stimulation on Temporal Processing Abilities in Individuals with Normal Hearing

The aim of the article was to compare the conditions of silent and contralateral noise on the temporal processing parameters. A total of 40 participants (20 males and 20 females) were enrolled in the study with a mean age of 21.7 years, participants with normal hearing thresholds and no history of middle ear pathology were enrolled for the study. The temporal processing tests such as duration discrimination test, gap detection test, and temporal modulation transfer function tests were carried out in these 40 individuals in the two conditions of silent and contralateral noise using MATLAB. Statistical analysis was carried out using the SPSS version 25.0 were descriptive and inferential statistics were carried out. Data was normally distributed on the Shapiro-Wilk's test of normality due to which a paired t test was carried out to establish the nature of significance between the silent and contralateral noise condition. Results reveal the presence of significant difference (p < 0.01) between the groups for all the parameters of temporal resolution with contralateral noise condition performing better than silent condition for the parameters. There is a positive effect of the efferent auditory pathway on the temporal resolution parameters thus implying that speech perception in noise is improved in the presence of background noise for normal hearing individuals due to this effect.

Reliability of Contralateral Suppression in Evoked Distortion Product Otoacoustic Emissions

Introduction  Distortion product otoacoustic emissions (DPOAE) and their suppression may be considered useful in monitoring cochlear function and the efferent auditory pathway inhibitory effect. Nonetheless, the establishment of reliable parameters of response variations is of great importance. Objectives  To verify the replicability of test and retest in the research of the inhibitory effect of the efferent pathway using contralateral suppressing stimulus during DPOAE recording for clinical applicability. Methods  Cross-sectional study with 48 volunteers, aged 18 to 30 years, with normal audiometric thresholds. The procedures included were audiometric and immittance measures to overrule any conductive or sensorineural conditions and DPOAE recordings without and with contralateral suppression with a 60 dBHL white noise. Distortion product otoacoustic emissions amplitudes were analyzed and compared in both conditions with Wilcoxon test, and the Spearman correlation test was used to assess test-retest reliability. Results  The comparative analysis showed differences between amplitudes in test and retest conditions only in 1,500 Hz for DPOAE measures with all other tested frequencies showing no differences, and no difference was observed in all recorded frequencies in the test and retest comparison for DPOAE suppression. The degree of correlation between test and retest of DPOAE amplitude was good at 6,000 Hz and strong (r > 0.880) at the other frequencies. For DPOAE with suppression, all frequencies presented strong correlation between test and retest: 1,500 Hz (r = 0.880), 2,000 Hz (r = 0.882), 3,000 Hz (r = 0.940), and 6,000 Hz (r = 0.957). Conclusions  The study found good replicability in contralateral suppression of DPOAE with potential clinical applicability, and we recommend conducting the test from 2000Hz to higher frequencies for more reliable results.

Lateralidade da atividade do sistema olivococlear medial eferente: estudo preliminar

RESUMO: Objetivo: avaliar a diferença na supressão das emissões otoacústicas entre as orelhas direita e esquerda. Métodos: participaram da pesquisa 36 indivíduos, sendo 18 destros e 18 canhotos, todos sem queixa auditiva e com audição dentro dos padrões de normalidade. A coleta de dados foi realizada por meio das emissões otoacústicas transientes e pela supressão das emissões otoacústicas. A análise da presença/ausência do efeito de supressão foi realizada baseada no valor obtido em response. Resultados: não houve diferença entre a orelha direita e esquerda para os valores de response das emissões otoacústicas com ruído contralateral para os indivíduos destros e canhotos. No gênero masculino houve diferença entre a orelha direita e esquerda para os valores de response das emissões otoacústicas com ruído contralateral. Conclusão: a avaliação realizada por meio da supressão das emissões otoacústicas não evidenciou diferenças entre as orelhas direita e esquerda nos grupos estudados.

The role of the efferent auditory system in developmental dyslexia

OBJECTIVE

To assess the role of the efferent auditory system by inhibition of contralateral otoacoustic emission in dyslexic children with auditory processing disorders.

METHODS

The study sample was 34 children: 17 with dyslexia and 17 age-matched controls. Sensitive speech tests (low-pass filtered, time-compressed, distorted and dichotic) were performed to assess coexisting auditory processing disorder. Distortion-product otoacoustic emission (DPOAE) values were measured in basal condition and with contralateral broadband noise signal delivered via an earphone transducer at 60 dB SPL.

RESULTS

The lower scores at sensitive speech testing confirmed the association of an auditory processing disorder in the dyslexic children. DPOAE values were significantly attenuated by contralateral inhibition only in the control group (p=0.001; dyslexics, p=0.19); attenuation was not significant at any frequency in the dyslexic group.

CONCLUSIONS

The differences in DPOAE attenuation between the groups, although not statistically significant, suggest alterations in the auditory efferent system in the dyslexic population. These alterations may affect language perception. If confirmed in further studies with larger samples, these results could provide insight into a possible pathophysiological background of dyslexia.

Avaliação do processamento auditivo temporal em trabalhadores rurais expostos a agrotóxicos organofosforados

OBJETIVO: Avaliar o processamento auditivo temporal em trabalhadores expostos ocupacionalmente a agrotóxicos organofosforados. MÉTODOS: Estudo descritivo transversal. Foram avaliados 43 trabalhadores rurais, de ambos os gêneros, expostos ao organofosforado, com limiares audiométricos normais bilateralmente. Os procedimentos realizados incluíram os seguintes itens: questionário sobre a história pessoal e laboral, período de exposição ao organofosforado, meatoscopia, e audiometria tonal liminar. Para avaliação do processamento auditivo temporal foram utilizados os seguintes testes: Teste de Padrão de Frequência, Teste de Padrão de Duração e Gaps-In-Noise. Além do desempenho, estudou-se a diferença entre as orelhas direita e esquerda no Gaps-In-Noise e a faixa de escolaridade em todos os testes. RESULTADOS: O desempenho da maior parte dos trabalhadores nos testes de processamento auditivo temporal foi inferior em relação aos padrões de normalidade. No teste Gaps-In-Noise, não houve diferença entre as orelhas (p=0,33). Em relação à escolaridade, não houve diferença em nenhum dos testes (Gaps-In-Noise: p=0,21 na orelha direita e p=0,053 na orelha esquerda; Teste de Padrão de Frequência: p=0,37; e Teste de Padrão de Duração: p=0,84). CONCLUSÃO: As habilidades auditivas de resolução temporal e ordenação temporal mostram-se comprometidas em indivíduos expostos ao organofosforado, mesmo estes apresentando audição periférica normal.