Cortical electric response audiometry hearing threshold estimation: accuracy, speed, and the effects of stimulus presentation features.
ABSTRACT A number of stimulus presentation features of the tone burst-evoked N1-P2 cortical response were investigated to identify any advantage over simple stimulation when the test is used for hearing threshold estimation. The speed of establishing objective thresholds at 1, 3, and 8 kHz in both ears was also measured in what was designed to be an efficient test protocol, together with the precision of the threshold estimates with reference to subjects' conventional audiograms.
Twenty-four volunteer subjects were recruited and tested by both behavioral and electrophysiological methods. A low-intensity, 3-kHz stimulus was used when the stimulus features were studied. The parameter was the N1-P2 amplitude.
Changing the side of presentation (randomly or by alternating ears), varying the interstimulus interval and inserting a 10-second recovery period midway though an averaging run had no demonstrable effect on response amplitude, both individually or in combination, contrary to earlier reports. Establishing the 6 threshold estimates took an average 20.6 minutes. The mean error in the N1-P2 threshold estimate was 6.5 dB, with no significant effect of frequency. After correcting for this bias, 94% of individual threshold estimates were within 15 dB of the behavioral threshold and 80% were within 10 dB.
This study suggests that cortical electric response audiometry has a performance that is as good as or better than the auditory brain stem response for threshold estimation in adults and that sophisticated stimulation techniques do not appear to be required. An efficient test protocol that automates many laborious tasks reduces the test time to less than half that previously reported in the literature for this response.
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ABSTRACT: Aging is often accompanied by hearing loss, which impacts how sounds are processed and represented along the ascending auditory pathways and within the auditory cortices. Here, we assess the impact of mild binaural hearing loss on the older adults' ability to both process complex sounds embedded in noise and to segregate a mistuned harmonic in an otherwise periodic stimulus. We measured auditory evoked fields (AEFs) using magnetoencephalography while participants were presented with complex tones that had either all harmonics in tune or had the third harmonic mistuned by 4 or 16% of its original value. The tones (75 dB sound pressure level, SPL) were presented without, with low (45 dBA SPL), or with moderate (65 dBA SPL) Gaussian noise. For each participant, we modeled the AEFs with a pair of dipoles in the superior temporal plane. We then examined the effects of hearing loss and noise on the amplitude and latency of the resulting source waveforms. In the present study, results revealed that similar noise-induced increases in N1m were present in older adults with and without hearing loss. Our results also showed that the P1m amplitude was larger in the hearing impaired than in the normal-hearing adults. In addition, the object-related negativity (ORN) elicited by the mistuned harmonic was larger in hearing impaired listeners. The enhanced P1m and ORN amplitude in the hearing impaired older adults suggests that hearing loss increased neural excitability in auditory cortices, which could be related to deficits in inhibitory control.Frontiers in Systems Neuroscience 01/2014; 8:8. DOI:10.3389/fnsys.2014.00008
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ABSTRACT: Cortical auditory evoked potentials (CAEPs) are an emerging tool for hearing aid fitting evaluation in young children who cannot provide reliable behavioral feedback. It is therefore useful to determine the relationship between the sensation level of speech sounds and the detection sensitivity of CAEPs, which is the ratio between the number of detections and the sum of detections and non-detections. Twenty-five sensorineurally hearing impaired infants with an age range of 8 to 30 months were tested once, 18 aided and 7 unaided. First, behavioral thresholds of speech stimuli /m/, /g/, and /t/ were determined using visual reinforcement orientation audiometry. Afterwards, the same speech stimuli were presented at 55, 65, and 75 dB sound pressure level, and CAEPs were recorded. An automatic statistical detection par-adigm was used for CAEP detection. For sensation levels above 0, 10, and 20 dB respectively, detection sensitivities were equal to 72±10, 75±10, and 78±12%. In 79% of the cases, automatic detection P-values became smaller when the sensation level was increased by 10 dB. The results of this study suggest that the presence or absence of CAEPs can provide some indication of the audibility of a speech sound for infants with sensorineural hearing loss. The detection of a CAEP might provide confidence, to a degree commensurate with the detec-tion probability, that the infant is detecting that sound at the level pre-sented. When testing infants where the audibility of speech sounds has not been established behaviorally, the lack of a cortical response indicates the possibility, but by no means a certainty, that the sensa-tion level is 10 dB or less.01/2012; DOI:10.4081/audiores.2012.e13
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ABSTRACT: Cortical auditory evoked potentials (CAEPs) are considered the electrophysiological equivalent of the pure tone audiogram (PTA) and can be used to assess the functional consequences of auditory deprivation and hearing aid acclimatization. Objectives: Threshold estimation and central auditory system evaluation in normal hearing children and those with hearing loss using cortical auditory evoked potentials. Study design: This work involved two groups: GI (20 normal hearing children) and GII (36 children with moderately-severe flat sensorineural hearing loss. The second group was divided into two subgroups: GIIa (20 children fitted with hearing aids) and GIIb (16 children not yet fitted with a hearing aid). Methodology: Basic audiological evaluation and CAEPs using speech and tone stimuli were performed and compared. The latencies and amplitude of different CAEP components were compared between both groups at the same sensation level. Results: GIIb showed a larger difference at 500 Hz compared to other frequencies, in contrast to GI and GIIa. CAEP latencies were significantly delayed in GIIb compared to GI or GIIa but CAEP amplitude showed no significant difference. Conclusions: Tone or speech evoked-cortical potentials can be used for threshold estimation in children with a high degree of consistency across different frequencies. Hearing aids can impact on cortical processing of simple or complex stimuli.Audiological Medicine 08/2012; 10(3). DOI:10.3109/1651386X.2012.699610