Biomedical subjects

D R Stapells

Publications and source records attributed to D R Stapells.

10 recordsLinked to original sources

PubMed1992

Interaction of click intensity and cochlear hearing loss on auditory brain stem response wave V latency.

Auditory brain stem responses (ABRs) to 95, 80, 60, 40, and 30 dB nHL clicks were retrospectively studied from 103 patients (194 ears) with various degrees of cochlear impairment. Hearing loss and sample size were balanced across gender. Results indicate that the slope of the wave V latency versus 4000 Hz hearing loss function doubles as click intensity is decreased from 80 (0.01 msec/dB HL) to 60 nHL (0.02 msec/dB HL). Overall results indicate a slope increase of 0.0004 msec for each decibel decrease in click intensity from 95 to 30 dB nHL. Intersubject variability increased with increased hearing loss and/or decreased stimulus intensity. The effects of hearing loss on wave V latency are minimal, and intersubject variability is less if high-intensity clicks (greater than or equal to 95 dB nHL) are used. No differences in the effects of hearing loss on wave V latency were seen between males and females. Latency corrections for cochlear hearing loss should, therefore, consider stimulus intensity.

Acoustic Stimulation↗

PubMed1992

Frequency specificity of the auditory brain stem response to bone-conducted tones in infants and adults.

Auditory brain stem responses were obtained from normal-hearing infants and adults in response to bone-conducted 500 and 2000 Hz tones presented in quiet and high-pass noise masking. The tones were presented at 70 (500 and 2000 Hz) and 46 (2000 Hz) dB peak to peak equivalent (re: 1 dyne RMS). The high-pass noise-masked waveforms were subtracted in succession to obtain derived responses, providing estimates of the cochlear regions contributing to the nonmasked responses. Findings indicate that the auditory brain stem response to bone-conducted 500 Hz tones is frequency specific for both infants and adults. For 2000 Hz tones, the results show maximum amplitudes for cochlear regions representing the nominal frequency of the tone for adults. For infants, maximum response amplitudes for the derived responses to 2000 Hz, 70 dB tones were obtained within 1/2 octave of the nominal frequency (1410-2000 Hz). Wave V latencies of the derived responses are similar for both groups for 2000 Hz tones, but shorter for infants to 500 Hz tones, supporting the hypothesis that low-frequency bone-conducted stimuli are effectively more intense in infants than adults.

Acoustics↗

PubMed1991

Maturation of the contralaterally recorded auditory brain stem response.

Ipsilaterally and contralaterally recorded auditory brain stem responses to 80 dB nHL clicks were recorded from 37 infants, aged 2 weeks to 20 mo and from six adults, all with normal auditory function. With increasing age, contralateral waves A, B, C, and D and ipsilateral waves III and V decreased in latency, with the contralateral morphology more closely resembling the ipsilateral morphology as age increased, especially after the age of 9 mo. The mean latencies and their change with age for waves A and B resembled those of ipsilateral waves III and III', respectively; both waves C and D demonstrated similarities with wave V. Large waveform changes were seen with maturation in the latency region of contralateral waves C and D. In 42 of 43 subjects, wave V latency occurred after wave C and before wave D. Peak to peak amplitudes of contralateral waves A-B and D-E' increased with age, but were smaller than those of ipsilateral I'-III and V-V', respectively. The smaller contralateral responses make their use for threshold estimation problematic, especially before the age of 9 months. The contralateral response, however, may help to select wave V in ambiguous cases, and to determine response laterality.

Acoustic Stimulation↗

PubMed1991

The human auditory steady-state evoked potentials.

When auditory stimuli are presented at rates near 40/s, they evoke a steady-state middle latency response. This results from the super-position of the transient responses evoked by each of the rapidly presented stimuli. The steady-state evoked potentials are most appropriately analyzed using frequency-based techniques. The response is larger for stimuli of higher intensity and of lower tonal frequency. The amplitude of the response varies with the state of arousal of the subject. Sleep results in a decrease in the amplitude to between one third and one half of the amplitude during wakefulness. The response is even further attenuated by general anesthesia. This auditory steady-state evoked potential may therefore be helpful in monitoring the state of arousal of a patient undergoing anesthesia.

Adult↗

PubMed1991

Evoked potential assessment of auditory system integrity in infants.

One child in 750 is born with a handicapping hearing impairment. The methods available to screen and evaluate infants at risk (auditory brainstem responses, middle latency responses, and cortical auditory evoked potentials) are reviewed, explained, and illustrated with case histories.

Audiometry, Evoked Response↗

PubMed1990

Thresholds for short-latency auditory-evoked potentials to tones in notched noise in normal-hearing and hearing-impaired subjects.

The thresholds for the short-latency auditory evoked potentials (SLAEPs) to short-duration tones presented in notched-noise masking were evaluated in 20 normal-hearing and 20 hearing-impaired subjects. The differences (dB) between these thresholds (dB nHL) and the pure-tone behavioral thresholds (dB HL) across all 40 subjects were 11.6, 6.1, 6.3 and 0.8 dB for 500, 1,000, 2,000 and 4,000 Hz, respectively. These differences were significantly smaller for the hearing-impaired subjects than for the normal-hearing subjects. Ninety-eight percent of the SLAEP threshold estimations were within 30 dB of the subjects' pure-tone behavioral thresholds and 91% were within 20 dB.

Adolescent↗

PubMed1989

Auditory brain stem responses to bone-conducted tones in infants.

The auditory brain stem responses (ABRs) to 500- and 2,000-Hz bone-conducted (BC) tones were recorded from 48 infants with ears exhibiting various external and middle ear states (normal, otitis media, auditory meatal atresia). Amplitudes were greater, wave V latencies longer, and detectability better for responses to 500-Hz BC tones compared to 2,000-Hz BC tones. Overall, most (94% to 100%) infants with normal cochlear sensitivity demonstrate ABRs to 20-dB normal hearing level (nHL) 500-Hz BC tones and 30-dB nHL 2,000-Hz BC tones. In cases in which masking is difficult (eg, bilateral atresia), infant ipsilateral/contralateral ABR asymmetries may help determine from which cochlea a response to the BC tones originates. In conclusion, two-channel ABR recordings to BC tones appear to be feasible for demonstrating normal cochlear sensitivity in infants.

Audiometry, Evoked Response↗

PubMed1988

Otitis media, auditory sensitivity, and language outcomes at one year.

The relationship among otitis media, auditory sensitivity, and emerging language was examined in a group of 1-year-old children who were prospectively followed since birth. Pneumatic otoscopy was used to document the otologic status of the children's ears at each medical visit. There were 13 babies with normal ratings in each ear at 80% more of their visits (designated as "otitis free") and 12 babies with bilaterally positive otoscopy results at 30% or more of their first year visits (designated "otitis positive"). In comparison to the otitis free infants, the group of otitis positive babies demonstrated reduced auditory sensitivity as measured by auditory brain stem response (ABR) and poorer expressive language abilities. However, differences in receptive language were not detected. These results suggest that otitis media may have an impact on auditory sensitivity and developing language as early as 1 year of age.

Audiometry, Evoked Response↗

PubMed1987

Auditory steady-state responses: threshold prediction using phase coherence.

These experiments add a measure of response phase variance--'phase coherence'--to the analysis procedures applied to auditory steady-state responses (SSR). The effects of stimulus frequency, intensity, rate and total number (i.e., recording time) were studied using 11 normal adult subjects. In a first experiment, SSR phase coherence was found to be highest at presentation rates near 40/sec, even when response amplitudes were higher at other rates. Further, phase coherence was observed to be linearly related (r = 0.91) to signal-to-noise ratio. Two further experiments demonstrated that phase coherence can correctly detect responses to near-threshold stimuli. In 15 min runs, significant phase coherence was detected within 6 dB of behavioral threshold in 6 subjects for 0.5 and 2.0 kHz signals, while phase coherence in no-stimulus control runs did not reach significance. Minimum data collection time required to record significant (P less than 0.01) responses was studied for 10 subjects. In 2 of 40 recordings at 10 dB SL phase coherence remained insignificant after even 15 min. However, average recording time to reach significance at 10 dB SL was less than 4 min in 38 of 40 recordings, and less than 1 min at 25 dB SL (18 of 18 recordings). These results indicate that using phase coherence to detect the presence of the 40/sec auditory steady-state response, efficient threshold search procedures may be devised to provide fast, accurate, and objective estimates of auditory behavioral thresholds in nearly all normal adults.

Acoustic Stimulation↗

PubMedDate not supplied

Inconsistency of auditory middle latency and steady-state responses in infants.

Auditory middle latency and steady-state responses (MLR/SSRs) were recorded in normal infants (aged 3 weeks to 28 months) and adults. SSR amplitudes were maximum using stimulus presentation rates near 40 Hz in adults. By contrast, the infant data showed no consistent amplitude maximum across the rates tested (9-59 Hz). With the exception of the brain-stem response wave V to MLR Na deflection, MLR components in infants' responses to 10.85 Hz clicks did not show any consistent pattern. To investigate the hypothesis that the 40 Hz SSR is derived from overlapping of the 10 Hz MLR components, 43.4 Hz SSRs were synthesized from the responses recorded at 10.85 Hz and compared with those recorded at 43.4 Hz. The predictive accuracy of the synthesized 43.4 Hz SSRs was significantly better in adults than in infants. The results of these studies indicate the presence of large age-related differences in the auditory MLR and SSR, and in the relationship between the two responses.

Acoustic Stimulation↗