Does the Number of Stimuli Influence the Formation of the Endogenous Components of the Event-Related Auditory Evoked Potentials?

Abstract Introduction The number of stimuli is important to determine the quality of auditory evoked potential records. However, there is no consensus on that number in studies, especially in the sample studied. Objectives To investigate the influence of the number of rare stimuli on forming N2 and P3 components, with different types of acoustic stimuli. Methods Cross-sectional, descriptive, comparative study, approved by the ethics committee of the institution. The sample comprised 20 normal hearing adults of both sexes, aged 18 to 29 years old, with normal scores in the mental state examination and auditory processing skills. The event-related auditory evoked potentials were performed with nonverbal (1 kHz versus 2 kHz) and verbal stimuli (/BA/ versus /DA/). The number of rare stimuli varied randomly in the recordings, with 10, 20, 30, 40, and 50 presentations. Results P3 latency was significantly higher for nonverbal stimuli with 50 rare stimuli. N2 latency did not show any difference between the type and number of stimuli. The absolute P3 and N2-P3 amplitudes showed significant differences for both types of stimuli, with higher amplitude for 10 rare stimuli, in contrast with the other ones. The linear tendency test indicated significance only for the amplitude - as the number of rare stimuli increased, the amplitude tended to decrease. Conclusion The components were identifiable in the different numbers of rare stimuli and types of stimuli. The P3 and N2-P3 latency and amplitude increased with fewer verbal and nonverbal stimuli. Recording protocols must consider the number of rare stimuli.

Differences and similarities in the long-latency auditory evoked potential recording of P1-N1 for different sound stimuli / Diferenças e similaridades no registro do potencial evocado auditivo P1-N1 para distintos estímulos sonoros

ABSTRACT Purpose: this study aimed at illustrating the similarities and differences in the recording of components P1 and N1 for verbal and non-verbal stimuli, in an adult sample population, for reference purposes. Methods: twenty-one adult, eutrophic individuals of both sexes were recruited for this study. The long-latency auditory evoked potential was detected by bilateral stimulation in both ears, using simultaneous recording, with non-verbal stimuli and the syllable /da/. Results: for non-verbal and speech stimuli, N1 was identified in 100.0% of the participants, whereas P1 was observed in 85.7% and 95.2% individuals for non-verbal and speech stimuli, respectively. Significant differences were observed for the P1 and N1 amplitudes between the ears (p <0.05); the P1 component, in the left ear, was higher than that in the right ear, whereas the N1 component was higher in the right one. Regarding the stimuli, the amplitude and latency values of N1 were higher for speech, whereas in P1, different results were obtained only in latency. Conclusion: the N1 component was the most frequently detected one. Differences in latency and amplitude for each stimuli occurred only for N1, which can be justified by its role in the process of speech discrimination.

RESUMO Objetivo: caracterizar as similaridades e diferenças do registro das componentes P1 e N1 para os estímulos verbal e não verbal, em uma população adulta, para fins de referência. Métodos: foram estudados 21 sujeitos adultos jovens, eutróficos, de ambos os sexos. O potencial evocado auditivo de longa latência foi pesquisado com estimulação bilateral e registro simultâneo das duas orelhas, com o estímulo clique e a sílaba /da/. Resultados: a N1 foi identificada em 100,0% da população, para os estímulos clique e fala, enquanto que a P1 foi observada em 85,7% e 95,2% dos sujeitos, para os respectivos estímulos. Foram observadas diferenças significantes para a amplitude de P1 e N1 entre as orelhas (p <0.05), sendo na P1 os valores da esquerda superiores à direita e para N1 foi o inverso. Entre os estímulos os valores de amplitude e latência da N1 foram maiores para a fala, enquanto na P1, apenas a latência obteve resultados distintos. Conclusão: a componente N1 foi a mais frequente. Apenas para N1 a diferença entre os tipos de estímulos ocorreram para latência e amplitude, o que pode ser justificado pelo seu papel no processo da discriminação de fala.

P300: Waves Identification with and without Subtraction of Traces

Abstract Introduction The P300 test requires well-defined and unique criteria, in addition to training for the examiners, for a uniform analysis of studies and to avoid variations and errors in the interpretation of measurement results. Objectives The objective of this study is to verify whether there are differences in P300 with and without subtraction of traces of standard and nonstandard stimuli. Method We conducted this study in collaboration with two research electrophysiology laboratories. From Laboratory 1, we selected 40 tests of subjects between 7 44 years, from Laboratory 2, we selected 83 tests of subjects between 18 44 years. We first performed the identification with the nonstandard stimuli; then, we subtracted the nonstandard stimuli fromthe standard stimuli. The examiners identified the waves, performing a descriptive and comparative analysis of traces with and without subtraction. Results After a comparative analysis of the traces with and without subtraction, there was no significant difference when compared with analysis of traces in both laboratories, within the conditions, of right ears (p = 0.13 and 0.28 for differences between latency and amplitude measurements) and left ears (p = 0.15 and 0.09 for differences between latency and amplitude measurements) from Laboratory 1. As for Laboratory 2, when investigating both ears, results did not identify significant differences (p = 0.098 and 0.28 for differences between latency and amplitude measurements). Conclusion There was no difference verified in traces with and without subtraction. We suggest the identification of this potential performed through nonstandard stimuli.

O que sabemos das alterações auditivas centrais em crianças expostas ao álcool na gestação? Revisão sistemática / What we know of the central auditory disorders in children exposed to alcohol during pregnancy? Systematic review

RESUMO Objetivo Identificar os efeitos da ingestão de álcool na gestação sobre o sistema nervoso auditivo central em relação aos seus possíveis diagnósticos, Síndrome Fetal do Álcool, Síndrome Fetal do Álcool Parcial, Distúrbios ao Nascimento Relacionados ao Álcool e Distúrbio do Neurodesenvolvimento Relacionado ao Álcool, sua extensão e o método de avaliação auditiva. Estratégia de pesquisa Busca sistemática e integrativa nas bases de dados PubMed, LILACS e SciELO, com os termos em português e inglês “síndrome fetal do álcool”, “desordens relacionadas ao uso do álcool” associadas a “audição”. Critérios de seleção Dos 123 resumos identificados, foram seis selecionados, publicados até maio de 2015. Análise dos dados Foram elencados tópicos a serem respondidos, caracterização da casuística; o diagnóstico decorrente da exposição fetal nas crianças; método de avaliação auditiva; e resultados descritos. Resultados Entre as avaliações comportamentais, foram utilizados os testes dicóticos verbais com sílabas e com sentenças e o teste fala com ruído. Entre os testes eletrofisiológicos, no Potencial Evocado Auditivo de Tronco Encefálico, foi detectada alteração de sincronia neural, e no Potencial Evocado Auditivo de Longa Latência – P300, valores de latência precoces. Conclusão Existem evidências de que as crianças e adultos jovens expostos ao álcool na gestação apresentam sinais de comprometimento do sistema nervoso auditivo central, mas não foi possível caracterizar essas alterações nos diferentes subtipos diagnósticos do espectro. As vias auditivas corticais foram as mais investigadas e o método eletrofisiológico o mais utilizado, com um resultado inesperado em dois deles, a latência precoce da N2 e da P300.

ABSTRACT Purpose To identify the effects of alcohol intake during pregnancy on the central auditory nervous system in relation to their possible diagnosis, Fetal Alcohol Syndrome, partial Fetal Alcohol Syndrome, Alcohol-Related Birth Defects and Alcohol-Related Neurodevelopmental Disorder, his extension and the hearing assessment method. Research strategy Systematic and integrative review searched the databases PubMed, LILACS and SciELO, with terms in Portuguese and English “fetal alcohol syndrome”, “alcohol-related disorders” associated with “hearing”. Selection criteria: We identified 123 abstracts, six were selected and published until May 2015. Data analysis Were listed topics to be answered, characterization of the sample; the diagnosis result of fetal exposure; method of hearing assessment and described results. Results Among the behavioral assessments, Verbal Dichotic Tests with syllables and sentences and Speech in Noise Test, were used. Among the electrophysiological tests, the Brainstem Auditory Evoked Potential was detected change neural synchrony, and Long-Latency Auditory Evoked Potential – P300, early latency values. Conclusion There is evidence that children exposed to alcohol in utero present central auditory nervous system involvement signals, but it was not possible to identify the influence of different subtypes and their losses. Cortical auditory pathways were the most investigated and the electrophysiological method as used with an unexpected result in two of them, early N2 and P300 latency.

Variables in P300 recording: task type and electrode position

ABSTRACT Purpose To analyze the latency and amplitude of P300 responses obtained with electrodes positioned at Cz and Fz and in different tasks of infrequent stimulus identification in normal hearing individuals. Methods Forty adults of both genders participated in the study. Three recordings with three different tasks were obtained for the identification of the infrequent stimulus; simultaneous recordings were obtained from Cz and Fz positions. Results Cz position showed significantly greater amplitudes and lower latencies than Fz. Regarding the three tasks, only “pronouncing the word ’thin’” was different from “raising a finger”, with lowest latencies for the verbal task. Regarding amplitude, significantly higher values were observed for “raising a finger”, followed by “pronouncing the word ‘thin’” and mental counting. Conclusion Cz obtained the best values, highest amplitude and lowest latency. Lowest latencies were obtained for the task of “pronouncing the word ‘thin’” and the highest amplitudes were obtained for “raising a finger”.