Biomedical subjects

Patricia Van Roon

Publications and source records attributed to Patricia Van Roon.

4 recordsLinked to original sources

PubMed2006

Simultaneous latency estimations for distortion product otoacoustic emissions and envelope following responses.

The purpose of this research was to simultaneously estimate processing delays in the cochlea and brainstem using the same acoustic stimuli. Apparent latencies were estimated from ear canal measurements of 2f1-f2 distortion product otoacoustic emissions (DPOAEs), and scalp recordings of the f2-f1 envelope following response (EFR). The stimuli were equal level tone pairs (65 dB SPL) with the upper tone f2 set at either 900 or 1800 Hz to fix the initiation site of the DPOAE and EFR. The frequency of f1 was swept continuously between frequency limits chosen to keep the EFR response between 150 and 170 Hz. The average DPOAE latencies were 9.6 and 6.2 ms for f2 =900 and 1800 Hz, and the corresponding EFR latencies were 12.4 and 8.8 ms. In a control condition, a third (suppressor) tone was added near the DPOAE response frequency to evaluate whether the potential source at fdp was contributing significantly to the measured emission. DPOAE latency is the sum of both inward and outward cochlear delays. The EFR apparent latency is the sum of inward cochlear delay and neural processing delay. Neural delay was estimated as approximately 5.3 ms for both frequencies of stimulation.

Acoustic Stimulation↗

PubMed2005

Estimating audiometric thresholds using auditory steady-state responses.

Human auditory steady-state responses (ASSRs) were recorded using stimulus rates of 78-95 Hz in normal young subjects, in elderly subjects with relatively normal hearing, and in elderly subjects with sensorineural hearing impairment. Amplitude-intensity functions calculated relative to actual sensory thresholds (sensation level or SL) showed that amplitudes increased as stimulus intensity increased. In the hearing-impaired subjects this increase was more rapid at intensities just above threshold ("electrophysiological recruitment") than at higher intensities where the increase was similar to that seen in normal subjects. The thresholds in dB SL for recognizing an ASSR and the intersubject variability of these thresholds decreased with increasing recording time and were lower in the hearing impaired compared to the normal subjects. After 9.8 minutes of recording, the average ASSR thresholds (and standard deviations) were 12.6 +/- 8.7 in the normal subjects, 12.4 +/- 11.9 dB in the normal elderly, and 3.6 +/- 13.5 dB SL in the hearing-impaired subjects.

Adult↗

PubMed2002

Intracerebral sources of human auditory steady-state responses.

The objective of this study was to localize the intracerebral generators for auditory steady-state responses. The stimulus was a continuous 1000-Hz tone presented to the right or left ear at 70 dBSPL. The tone was sinusoidally amplitude-modulated to a depth of 100% at 12, 39, or 88 Hz. Responses recorded from 47 electrodes on the head were transformed into the frequency domain. Brain electrical source analysis treated the real and imaginary components of the response in the frequency domain as independent samples. The latency of the source activity was estimated from the phase of the source waveform. The main source model contained a midline brainstem generator with two components (one vertical and lateral) and cortical sources in the left and right supratemporal plane, each containing tangential and radial components. At 88 Hz, the largest activity occurred in the brainstem and subsequent cortical activity was minor. At 39 Hz, the initial brainstem component remained and significant activity also occurred in the cortical sources, with the tangential activity being larger than the radial. The 12-Hz responses were small, but suggested combined activation of both brainstem and cortical sources. Estimated latencies decreased for all source waveforms as modulation frequency increased and were shorter for the brainstem compared to cortical sources. These results suggest that the whole auditory nervous system is activated by modulated tones, with the cortex being more sensitive to slower modulation frequencies.

Acoustic Stimulation↗

PubMed2002

Estimating the audiogram using multiple auditory steady-state responses.

Multiple auditory steady-state responses were evoked by eight tonal stimuli (four per ear), with each stimulus simultaneously modulated in both amplitude and frequency. The modulation frequencies varied from 80 to 95 Hz and the carrier frequencies were 500, 1000, 2000, and 4000 Hz. For air conduction, the differences between physiologic thresholds for these mixed-modulation (MM) stimuli and behavioral thresholds for pure tones in 31 adult subjects with a sensorineural hearing impairment and 14 adult subjects with normal hearing were 14+/-11, 5+/-9, 5+/-9, and 9+/-10 dB (correlation coefficients .85, .94, .95, and .95) for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. Similar results were obtained in subjects with simulated conductive hearing losses. Responses to stimuli presented through a forehead bone conductor showed physiologic-behavioral threshold differences of 22+/-8, 14+/-5, 5+/-8, and 5+/-10 dB for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. These responses were attenuated by white noise presented concurrently through the bone conductor.

Adult↗