Abstract
Objective To study objectively auditory temporal processing in a group of normal hearing subjects and in a group of hearing-impaired individuals with auditory neuropathy (AN) using electrophysiological and psychoacoustic methods. Methods Scalp recorded evoked potentials were measured to brief silent intervals (gaps) varying between 2 and 50 ms embedded in continuous noise. Latencies and amplitudes of N100 and P200 were measured and analyzed in two conditions: (1) active, when using a button in response to gaps; (2) passive, listening, but not responding. Results In normal subjects evoked potentials (N100/P200 components) were recorded in response to gaps as short as 5 ms in both active and passive conditions. Gap evoked potentials in AN subjects appeared only with prolonged gap durations (10–50 ms). There was a close association between gap detection thresholds measured psychoacoustically and electrophysiologically in both normals and in AN subjects. Conclusions Auditory cortical potentials can provide objective measures of auditory temporal processes. Significance The combination of electrophysiological and psychoacoustic methods converged to provide useful objective measures for studying auditory cortical temporal processing in normals and hearing-impaired individuals. The procedure used may also provide objective measures of temporal processing for evaluating special populations such as children who may not be able to provide subjective responses.
Highlights
The ability to make fine temporal discriminations of acoustic signals contributes to a number of auditory perceptions including speech discrimination and the localization of sound
Temporal processing deficits measured by gap detection have been reported for older listeners (Schneider and Hamstra, 1999), children with dyslexia (Ingelghem et al, 2001), patients with sensorineural hearing loss (Nelson and Thomas, 1997), and individuals with auditory neuropathy (Zeng et al, 1999)
Accuracy and reaction time (RT) measures Accuracy in the active condition was affected by gap duration (F(4,40)Z75.0, P!0.001)
Summary
The ability to make fine temporal discriminations of acoustic signals contributes to a number of auditory perceptions including speech discrimination and the localization of sound. A popular method in psychoacoustics for measuring temporal processes is the threshold for detecting silent gaps in noise (for example, see Phillips, 1999). Middle-latency magnetic fields (Rupp et al, 2002) and cortical potentials (mismatch negativity or MMN) (Bertoli et al, 2001, 2002; Desjardins et al, 1999) have been recorded. These physiological measures are sensitive to temporal gaps, but they have not received extensive use for the objective assessment of
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