Rapid adaptation of the 2f1-f2 DPOAE in humans: binaural and contralateral stimulation effects.
The present data were collected in humans to characterize the effects of monaural and binaural stimulation and contralateral noise on the 2f1-f2 distortion-product otoacoustic emission (DPOAE) adaptation response. DPOAE levels (f2/f1=1.21, L1=70 dB SPL, L2=65 dB SPL) were measured in both ears for a range of f2 frequencies (1.2 to 10.0 kHz). The f2 frequency producing the largest amplitude DPOAE was used for further testing employing three different stimulus conditions: the primary tones were presented to only one ear for 4 s; the two tones were presented simultaneously in both ears; and, contralateral broadband noise (60 dB SPL) was presented for 5 s, beginning 4 s after the onset of the monaural primaries in the test ear. Acoustic reflex thresholds were measured to verify that the middle-ear muscles played no systematic role in the measured DPOAE reductions. Estimates of monaural rapid adaptation levels and time constants agreed well with previous human findings. The magnitude of the rapid adaptation under binaural stimulation, as compared with monaural primaries, was 25% greater on average, though adaptation time constants were comparable. With added contralateral noise, the average DPOAE suppression was 1.1 dB (0.3-2.7 dB). The magnitude of the monaural adaptation and the effects of binaural and contralateral stimulation, however, were smaller than those measured previously in experimental animals, though the time constants were in good agreement.
Bassim
Marc K
MK
Hearing Research Laboratories, Division of Otolaryngology-Head and Neck Surgery, Duke University Medical Center, Box 3550, Durham, NC 27710, USA.
Miller
Roger L
RL
Buss
Emily
E
Smith
David W
DW
D000161:Acoustic Stimulation; D000222:Adaptation, Physiological; D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D004525:Efferent Pathways / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D013997:Time Factors