Efeito do mascaramento modulado na avaliação dos potenciais evocados auditivos corticais e nos limiares auditivos comportamentais.

Abstract

Introduction: The study of the Masking Release phenomenon or Benefit of Modulated Masking in the electrophysiological and behavioral domains has enabled the improvement of research regarding temporal auditory processing abilities and the establishment of parameters for analyzing speech recognition in noise situations. In view of this, this research seeks, based on evidence, to support future studies related to the use of Cortical Auditory Evoked Potential associated with behavioral testing in investigating the phenomenon of noise modulation in the processes of auditory speech perception in the Brazilian population in different age groups. Objetive: to analyze whether modulated noise evokes better responses in cortical auditory evoked potentials and improves behavioral thresholds when compared to steady noise. Methodology: In order to support the experiments in this thesis, a systematic review with metaanalysis was initially carried out (Article I), aiming to investigate the behavior of cortical auditory evoked potentials in the face of modulated masking in the population with normal hearing. As for the original research of this thesis, it is an analytical, cross-sectional and observational study, carried out in the Audiology laboratory of the Speech Therapy Department of the Federal University of Pernambuco. The total research population was made up of 60 individuals, young, adults and elderly, between 18 and 75 years of age, of both sexes and with normal hearing. Individuals underwent the Modulated Masking Benefit assessment protocol using electrophysiological and behavioral measures. The electrophysiological assessment included the use of the Cortical Auditory Evoked Potential test with speech stimulus /ba/ presented simultaneously with speech noise (Speech Shaped Noise) in three conditions: a) stimulus and weak steady noise; b) stimulus and strong steady noise; c) stimulus and modulated noise. Morphology, latency and amplitude of cortical waves P1, N1 and P2 were analyzed, as well as the electrophysiological threshold in stable noise and modulated noise conditions. In the behavioral assessment, a sentence recognition test was used in the presence of steady and modulated noise, using the 12 lists (with 20 sentences each) of the HINT-Brazil test, in order to compare the effect of noise modulation in both domains. Results: the result of the systematic review (Article I) showed better responses in the behavior of cortical auditory evoked potentials in the face of modulated masking, expressed by a decrease in latency and an increase in amplitude. These results indicated a smaller effect of noise modulation on cortical auditory processing, highlighting the phenomenon of Modulated Masking Benefit. Partial results from 40 normal-hearing individuals between 18 and 50 years of age (Article II) showed less interference from modulated noise in latency and amplitude measurements of cortical components, generating a significant reduction in P1 latency and an increase in P1 amplitude. P2 in both groups of participants (young adults and adults). Furthermore, a greater magnitude of the Modulated Masking Benefit was observed in the younger group of participants. The final results of the research (Article III) showed better auditory threshold responses (electrophysiological and behavioral), compared to stable noise in all age groups. The elderly presented a higher threshold in both hearing domains, compared to the other participants, as well as a lower BMM magnitude. Conclusion: it was possible to conclude from the results that modulated noise directly and positively influences the cortical responses of the Cortical Auditory Evoked Potential, generating less interference in the magnitude of the neural response and in the neural processing time for the speech stimulus. The higher auditory thresholds (electrophysiological and behavioral) and the lower magnitude of the Modulated Masking Benefit observed in the elderly group, even in the face of noise modulation, suggest a lower temporal auditory performance in this population, and may indicate a deficit in temporal resolution capacity, associated with the aging process.