RESUMO
The amplitude modulation-following response (AMFR), an auditory evoked potential elicited by continuous amplitude-modulated tones, can be recorded for carrier frequencies across the audiometric range. AMFR thresholds (based on the amplitude spectra of the responses) have been found to closely follow behavioral thresholds in six normal-hearing and four hearing-impaired adults. In the current work, we studied the reliability of the AMFR as an index of behavioral low-frequency (500 and 1000 Hz) thresholds in a larger sample (n = 16) of hearing-impaired adults with mild to moderate hearing loss. The AMFR amplitudes and detection thresholds were strongly correlated across the two recording sessions, and AMFR thresholds obtained in both sessions were strongly correlated to behavioral thresholds. The average absolute difference between the AMFR and behavioral thresholds was 7.3 dB and 6.4 dB for 500 Hz and 1000 Hz, respectively.
Assuntos
Limiar Auditivo , Potenciais Evocados Auditivos , Perda Auditiva Neurossensorial/diagnóstico , Estimulação Acústica , Adulto , Audiometria de Tons Puros , Feminino , Audição/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , SonoRESUMO
The amplitude modulation-following response (AMFR) is an auditory scalp-recorded potential, evoked using continuous, amplitude-modulated tones. The current study was designed to explore the audiometric utility of the AMFR by demonstrating the frequency specificity of the response and assessing the relation between behaviorally measured pure-tone thresholds and AMFR detection thresholds. Subjects in this study were six normal-hearing and four hearing-impaired adults. High-pass masking results in the normal hearing subjects demonstrated that the AMFR is associated with a narrow range of activation along the cochlea around the carrier frequency. Frequency-specific results from the hearing-impaired subjects confirmed this finding. Thresholds for the AMFR, defined in spectral terms, were consistent with the behavioral estimates in both the normal and the hearing-impaired subjects.
Assuntos
Audiometria de Resposta Evocada/métodos , Limiar Auditivo , Potenciais Evocados Auditivos/fisiologia , Perda Auditiva Neurossensorial/fisiopatologia , Estimulação Acústica/métodos , Acústica , Adulto , Audiometria de Tons Puros , Comportamento , Cóclea/fisiologia , Feminino , Análise de Fourier , Perda Auditiva Neurossensorial/diagnóstico , Humanos , Masculino , Mascaramento PerceptivoRESUMO
The relation between the auditory brain stem potential called the frequency-following response (FFR) and the low pitch of complex tones was investigated. Eleven complex stimuli were synthesized such that frequency content varied but waveform envelope periodicity was constant. This was accomplished by repeatedly shifting the components of a harmonic complex tone upward in frequency by delta f of 20 Hz, producing a series of six-component inharmonic complex tones with constant intercomponent spacing of 200 Hz. Pitch-shift functions were derived from pitch matches for these stimuli to a comparison pure tone for each of four normal hearing adults with extensive musical training. The FFRs were recorded for the complex stimuli that were judged most divergent in pitch by each subject and for pure-tone signals that were judged equal in pitch to these complex stimuli. Spectral analyses suggested that the spectral content of the FFRs elicited by the complex stimuli did not vary consistently with component frequency or the first effect of pitch shift. Furthermore, complex and pure-tone signals judged equal in pitch did not elicit FFRs of similar spectral content.