Abstract
To analyze the presence of auditory cortical potential and its correlation with psychoacoustic detection of speech sounds as well as the latency of the P1, N1 e P2 components presented in free field in hearing impaired adults with and without amplification. We evaluated 22 adults with moderate to severe symmetrical bilateral sensorineural hearing loss, regular users of bilateral hearing aids. Speech sounds of low (/m/), medium (/g/) and high (/t/) frequencies were presented in sound field in decreasing intensities of 75, 65 and of 55 dBSPL in free field with and without hearing aids. The used equipment performs automatic statistical detection of the presence of response; forthermore, the latencies of waves P1, N1 e P2 were labeled and the psychoacoustic perception was registered. The results demonstrated the increased presence of cortical response with hearing aids. We observed the correlation between psychoacoustic perception and automatic detection of 91% for the sounds /g/ and /t/ and ranged from 73 to 86% for the sound /m/. The averages of latencies P1-P2-N1 decreased with both increasing intensity and the use of hearing aids for the three sounds. The differences were significant for the sounds /g/ and /t/ in comparison with and without hearing aids. There was increase in the presence of cortical auditory evoked potential with hearing aids. Automatic detection of cortical response provided with hearing aids showed 91% agreement with the psychoacoustic perception of the speech signal. In the analysis of latency measures of the P1, N1 and P2 components, it was observed a decrease with the increase of the signal intensity and the use of amplification for the three speech stimuli /m/, /g/ and /t/.
Highlights
The auditory evoked potentials (AEPs) are electrical modifications in the auditory nervous system, generated in several levels of the central auditory nervous system by an acoustic stimulus
The auditory assessment using the cortical auditory evoked potentials (CAEPs) presents several advantages, because it allows evaluating the whole auditory system and because it can be registered among awake participants, obtained with a variety of acoustic stimuli presented both with headphones and in free field, which is an especially favorable situation[1,3]
The results showed that the average of latencies of components P1, N1 and P2 reduced with the increasing intensity and with the use of hearing-aid devices for the three sounds /m/, /t/, and /g/
Summary
The auditory evoked potentials (AEPs) are electrical modifications in the auditory nervous system, generated in several levels of the central auditory nervous system by an acoustic stimulus. They are classified according to latency (interval of time between the presentation of the sound stimulus and wave peak) into three groups: short-latency potentials, occurring in the first 10–12 ms; middle-latency potentials, occurring between 12 and 50 ms; and long-latency potentials, called cortical potentials, occurring between 50 and 600 ms[1]. The most common exogenous cortical auditory evoked potentials (CAEPs) are P1, N1 e P2 These components provide information concerning the arrival of sound information to the auditory cortex[2]. By considering the significant maturational changes occurring in CAEP throughout development, the major variability of responses, besides the technical limitation of electrodes, filters, and amplifiers to capture these potentials, added to the difficulty to interpret responses and the high costs of the equipment, the clinical use of CAEP has been hampered until recently[3,4]
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