Biomedical subjects

Gary Rance

Publications and source records attributed to Gary Rance.

10 recordsLinked to original sources

PubMed2006

A comparison of 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) thresholds in awake adult subjects.

Evoked potential thresholds using the 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) were recorded at 500 Hz and 4000 Hz test frequencies in 36 subjects with normal acuity, and 30 subjects with sensorineural hearing loss. ASSR threshold sensation levels (SLs) were lower in ears with greater degrees of hearing loss, and for the 500 Hz stimulus. Mean SLs (maximum duration of a single recording: 89 seconds) were as follows at 500 Hz and 4000 Hz respectively: normal hearing group, 16.9+/-10.3 dB and 42.4+/-14.4 dB; mild-moderate group, 10.6+/-8.8 dB and 23.8+/-8.1 dB; severe-profound group, 10.0+/-13.2 dB and 21.5+/-18.9 dB. CAEP SLs showed no change with hearing level and CAEP/behavioural differences were similar at each test frequency. Mean SLs for CAEP threshold (single recording duration: 84 seconds) at 500 Hz and 4000 Hz respectively were: normal hearing group, 10.3+/-6.4 dB and 11.5+/-3.8 dB; mild-moderate group, 8.4+/-7.4 dB and 13.2+/-12.4 dB; severe-profound group, 11.0+/-6.6 dB and 15.9+/-16.4 dB. The results of this study suggest that while both 40 Hz ASSR and CAEP can reflect the behavioural audiogram, CAEPs may provide a more reliable estimate of hearing in awake adults.

Acoustic Stimulation↗

PubMed2006

Maturation of auditory steady-state responses in normal babies.

OBJECTIVE: To track the development of the auditory steady-state response (ASSR) through the neonatal and early infant periods in a group of normal-hearing babies. DESIGN: This longitudinal study involved assessment at four data collection points. ASSR thresholds to modulated 500 Hz and 4 kHz tones were established in 20 full-term subjects at 0, 2, 4, and 6 wks of age. RESULTS: Significant developmental changes were observed for both test frequencies. Mean ASSR threshold levels decreased by approximately 10 dB between the week 0 and week 6 data collection points. CONCLUSIONS: The results of this study indicate that ASSR threshold levels in normal-hearing neonates and young infants are different from those observed in older subjects. Clinical application of the ASSR procedure in this population will need to take into account developmental changes occurring in the first weeks of life. Furthermore, the findings indicate that ASSR thresholds in normal-hearing babies at 6 wks of age are not yet mature.

Age Factors↗

PubMed2006

Comparison of auditory steady-state responses and tone-burst auditory brainstem responses in normal babies.

OBJECTIVE: To follow the development of tone-burst auditory brainstem response (TB-ABR) and auditory steady-state response (ASSR) thresholds in a group of normal babies through the first 6 wk of life. DESIGN: This longitudinal study involved assessment at four data-collection points. TB-ABR and ASSR thresholds to 500-Hz and 4-kHz stimuli were established in 17 full-term subjects at 0, 2, 4, and 6 wk of age. Stimulus-modulation rates for ASSR assessment were 74 Hz (for 500-Hz tones) and 95 Hz (for 4-kHz tones). TB-ABR responses were recorded to stimuli presented at 39.1 Hz. RESULTS: Mean ASSR thresholds (calibrated in dBHL) at 500 Hz ranged from 44.4 to 39.7 dB HL across the recording period, and at 4 kHz they ranged from 37.9 to 32.1 dB HL. TB-ABR thresholds (calibrated in dBnHL) were significantly lower, ranging from 36.8 to 36.2 dB nHL at 500 Hz and from 16.5 to 15.9 dB nHL at 4 kHz. However, when the stimuli used for each test were calibrated in the same units (peak equivalent dB SPL), the results were similar. That is, the differences between the two techniques were only an artifact of the calibration. ASSR thresholds were more variable than TB-ABR, particularly at the neonatal measurement point. Within-subject changes across the test period were observed for ASSR thresholds but not for TB-ABR. CONCLUSIONS: The longitudinal findings presented in this study suggest that for normal neonates, the TB-ABR technique may offer a more reliable basis for prediction of hearing levels than ASSR assessment. This is not because TB-ABR thresholds (calibrated in dBnHL) are lower, but because the response is less affected by maturational development in the first weeks of life and is less variable across subjects.

Acoustic Stimulation↗

PubMed2005

Auditory neuropathy/dys-synchrony and its perceptual consequences.

Auditory neuropathy/dys-synchrony is a form of hearing impairment in which cochlear outer hair cell function is spared but neural transmission in the auditory pathway is disordered. This condition, or group of conditions with a common physiologic profile, accounts for approximately 7% of permanent childhood hearing loss and a significant (but as yet undetermined) proportion of adult impairment. This paper presents an overview of the mechanisms underlying auditory neuropathy/dys-synchrony-type hearing loss and the clinical profile for affected patients. In particular it examines the perceptual consequences of auditory neuropathy/dys-synchrony, which are quite different from those associated with sensorineural hearing loss, and considers currently available, and future management options.

Adult↗

PubMed2005

Hearing threshold estimation in infants using auditory steady-state responses.

Successful early intervention in children with permanent hearing loss requires assessment techniques that can accurately reflect the behavioral audiogram in infancy. This retrospective study compared auditory steady-state response (ASSR) findings from subjects tested in the first three months of life with subsequently obtained behavioral hearing levels. ASSR audiograms were established using amplitude and frequency modulated tones at octave frequencies (500 Hz to 4 kHz). Results obtained from 575 subjects including 285 with normal hearing, 271 with sensorineural hearing loss, and 19 with auditory neuropathy-type hearing loss are presented. ASSR and behavioral hearing thresholds for subjects in the normal and sensorineural groups were highly correlated, with Pearson r values exceeding 0.95 at each of the test frequencies. In contrast, ASSR thresholds in children with AN-type hearing loss did not accurately reflect the behavioral audiogram. Overall, the findings indicate that ASSR testing can offer useful insights into the hearing acuity of children tested in infancy.

Acoustic Stimulation↗

PubMed2004

Perceptual characterization of children with auditory neuropathy.

OBJECTIVE: To characterize the perceptual abilities of a group of children with auditory neuropathy (AN)-type hearing loss, correlating results on a range of psychophysical tasks with open-set speech perception performance. DESIGN: Frequency resolution, temporal resolution and frequency discrimination ability was assessed in a group of 14 children with AN. Data also were obtained from a cohort of matched subjects with sensorineural hearing loss, and from a group of normally hearing children. RESULTS: Frequency resolution (notched noise masking) results for the AN subjects were equivalent to those of the normal-hearing subjects reflecting the "normal" outer hair cell function that characterizes the AN condition. Temporal resolution (TMTF) findings were, however, abnormal in many AN subjects and the degree of temporal disruption was correlated with speech discrimination (CNC) score. Frequency discrimination ability (for both fixed and frequency modulated stimuli) was also affected in those children with poor temporal resolution. CONCLUSIONS: The findings of this study indicate that the perceptual profiles of children with AN are quite different from those with sensorineural hearing loss. Where subjects in the latter group presented with impaired frequency resolution and normal temporal processing, the AN subjects typically showed normal frequency resolution and varying degrees of temporal disruption. The severity of this temporal abnormality, which appeared to affect both temporal resolution/amplitude modulation detection and the temporal aspects of frequency discrimination (such as phase locking), was strongly correlated to speech perception performance.

Audiometry, Speech↗

PubMed2002

Speech perception and cortical event related potentials in children with auditory neuropathy.

OBJECTIVES: 1) To investigate the unaided and aided speech perception abilities of children with auditory neuropathy (AN) and to compare their performance to children with sensorineural hearing loss. 2) To establish whether cortical event related potentials (ERPs) could be recorded in children with AN, and to determine the relationship between the presence of these responses and speech perception. DESIGN: Unaided and aided speech perception assessments (PBK words), and cortical-ERP testing was carried out in a group of 18 children with AN. Data also were obtained from a cohort of age and hearing level matched children with sensorineural hearing loss. RESULTS: The speech perception performance of the 15 children with AN able to complete a PBK-word assessment, fell into two distinct categories. The children either showed no open-set speech perception ability (7/15 cases), or performance levels similar to their sensorineural counterparts (8/15 cases). Approximately 50% of children with AN showed ERPs of normal latency, amplitude and morphology. In all cases, response presence (at normal latencies) was consistent with reasonable speech perception ability, and response absence was consistent with negligible speech perception. CONCLUSIONS: In approximately 50% of children with auditory neuropathy, the provision of amplification results in significant open-set speech perception improvements. The results confirm the previously published reports that speech perception ability cannot be reliably estimated from the behavioral audiogram in children with AN. Obligatory ERP test results may offer a means of predicting perceptual skills in newly diagnosed youngsters as the presence of ERPs (with age-appropriate latency and morphology) was correlated with significant open set speech perception abilities and amplification benefit. The absence of the ERP in contrast, indicated profound hearing disability evidenced by profound hearing loss and/or extremely poor speech perception.

Adolescent↗

PubMed2002

Assessment of hearing in infants with moderate to profound impairment: the Melbourne experience with auditory steady-state evoked potential testing.

Auditory steady-state evoked potential (ASSEP) testing has been used in the assessment of hearing in infants at the University of Melbourne School of Audiology Clinic during the past 10 years. This study examines the evoked potential and behavioral hearing test findings for 200 children in whom permanent, moderate to profound hearing loss was diagnosed with the ASSEP procedure. The ASSEP audiograms were obtained with amplitude and frequency modulated tones at octave frequencies (500 to 4,000 Hz). In 184 infants, the hearing loss appeared to be of sensorineural origin. For these children, there was a strong correlation between ASSEP findings and behavioral thresholds, with Pearson r coefficients ranging from 0.81 to 0.93 with test frequency. As such, the ASSEP findings obtained in the first months of life were accurate enough to form a basis for fitting amplification and early intervention. For the 16 children whose hearing loss appeared to be the result of auditory neuropathy, however, ASSEP thresholds showed little or no relationship to the behavioral audiogram.

Age Factors↗

PubMed2002

The auditory steady-state response: comparisons with the auditory brainstem response.

Two studies are reported in which the threshold estimates from auditory steady-state response (ASSR) tests are compared to those of click- or toneburst-evoked auditory brainstem responses (ABRs). The first, a retrospective review of 51 cases, demonstrated that both the click-evoked ABR and the ASSR threshold estimates in infants and children could be used to predict the pure-tone threshold. The second, a prospective study of normal-hearing adults, provided evidence that the toneburst-evoked ABR and the modulated tone-evoked ASSR thresholds were similar when both were detected with an automatic detection algorithm and that threshold estimates varied with frequency, stimulus rate, and detection method. The lowest thresholds were obtained with visual detection of the ABR. The studies illustrate that ASSRs can be used to estimate pure-tone threshold in infants and children at risk for hearing loss and also in normal-hearing adults.

Adult↗

PubMed2002

Prediction of hearing threshold in infants using auditory steady-state evoked potentials.

This retrospective study examines the relationship between auditory steady-state evoked potential (ASSEP) thresholds determined in infancy and subsequently obtained behavioral hearing levels in children with normal hearing or varying degrees of sensorineural hearing loss. Overall, the results from 211 subjects showed that the two test techniques were highly correlated, with Pearson r values exceeding .95 at each of the audiometric test frequencies between 500 and 4000 Hz. Analysis of the findings for babies with significant hearing loss (moderate to profound levels) showed similar threshold relationships to those obtained in previous studies involving adults and older children. The results for infants with normal or near-normal hearing did, however, differ from those reported for older subjects, with behavioral thresholds typically 10 to 15 dB better than would have been predicted from their ASSEP levels.

Acoustic Impedance Tests↗