Biomedical subjects

L M Moran

Publications and source records attributed to L M Moran.

4 recordsLinked to original sources

PubMed1998

Objective evaluation of aided thresholds using auditory steady-state responses.

Auditory steady-state responses to amplitude-modulated tones with modulation frequencies between 80 and 105 Hz can be recorded when multiple stimuli are presented simultaneously through a soundfield speaker and amplified using a hearing aid. Responses were recorded at carrier frequencies of 500, 1000, 2000, and 4000 Hz in a group of 35 hearing-impaired children using hearing aids. The physiologic responses were recorded at intensities close to the behavioral thresholds for sounds in the aided condition, with average differences between the physiologic and behavioral thresholds of 17, 13, 13, and 16 dB for carrier frequencies 500, 1000, 2000, and 4000 Hz. The technique shows great promise as a way to assess aided thresholds objectively in subjects who cannot reliably respond on behavioral testing.

Audiometry, Pure-Tone↗

PubMed1996

Frequency-specific audiometry using steady-state responses.

OBJECTIVE: To evaluate the audiometric usefulness of steady-state responses to multiple simultaneous tones, amplitude-modulated at 75 to 110 Hz. DESIGN: Steady-state responses to multiple tones amplitude-modulated at different rates between 75 and 110 Hz and presented simultaneously were recorded at different intensities in normal adults, well babies, normal adults with simulated hearing loss, and adolescents with known hearing losses. Response thresholds were compared with behavioral thresholds. RESULTS: In normal adults the thresholds for steady-state responses to tones of 0.5, 1, 2, and 4 kHz were 14 +/- 11, 12 +/- 11, 11 +/- 8, and 13 +/- 11 dB, respectively, above behavioral thresholds for air-conducted stimuli, and 11 +/- 5, 14 +/- 8, 9 +/- 8, and 10 +/- 10 dB above behavioral thresholds for bone-conducted stimuli. In well babies tested in a quiet environment, the thresholds were 45 +/- 13, 29 +/- 10, 26 +/- 8, and 29 +/- 10 dB SPL. In adolescents with known hearing losses, the steady-state responses thresholds predict behavioral thresholds with correlation coefficients (r) of 0.72, 0.70, 0.76, and 0.91 at 0.5, 1, 2, and 4 kHz, respectively. CONCLUSION: Steady-state responses to tone amplitude-modulated at 75 to 110 Hz can be used for frequency-specific objective audiometry. The multiple-stimulus technique allows thresholds to be estimated for eight different stimuli at the same time.

Adolescent↗

PubMed1994

Recording auditory brainstem responses from infants.

Auditory brainstem responses (ABRs) can be reliably recorded from infants in the first few months of life. Since they are normally recognizable down to intensities that are 30 dB above normal hearing thresholds, ABRs elicited by clicks are useful in screening for hearing-impairment in infancy. The ABRs can also provide further diagnostic information about the hearing losses that are detected by screening: the threshold for the response represents a reasonable estimate of the severity of the hearing loss; bone-conduction studies can assess the extent of a conductive loss; and frequency-specific techniques can evaluate hearing thresholds at different frequencies. At present, ABRs are mainly used for screening infants who have been treated in neonatal intensive care units. Because the majority of infants with hearing impairment are not seen in these units, it might be worthwhile to use ABRs in a more widespread screening program.

Evoked Potentials, Auditory, Brain Stem↗

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↗