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Comparative Study
. 2011 Dec;282(1-2):128-37.
doi: 10.1016/j.heares.2011.08.007. Epub 2011 Aug 26.

The relationship between MOC reflex and masked threshold

Angela Garinis  1 , Lynne Werner, Carolina Abdala
Affiliations
Comparative Study

The relationship between MOC reflex and masked threshold

Angela Garinis et al. Hear Res. 2011 Dec.

Abstract

Otoacoustic emission (OAE) amplitude can be reduced by acoustic stimulation. This effect is produced by the medial olivocochlear (MOC) reflex. Past studies have shown that the MOC reflex is related to listening in noise and attention. In the present study, the relationship between strength of the contralateral MOC reflex and masked threshold was investigated in 19 adults. Detection thresholds were determined for 1000-Hz, 300-ms tone presented simultaneously with one repetition of a 300-ms masker in an ongoing train of masker bursts. Three masking conditions were tested: 1) broadband noise 2) a fixed-frequency 4-tone complex masker and 3) a random-frequency 4-tone complex masker. Broadband noise was expected to produce energetic masking and the tonal maskers were expected to produce informational masking in some listeners. DPOAEs were recorded at fine frequency intervals from 500 to 4000 Hz, with and without contralateral acoustic stimulation. MOC reflex strength was estimated as a reduction in baseline level and a shift in frequency of DPOAE fine-structure maxima near 1000-Hz. MOC reflex and psychophysical testing were completed in separate sessions. Individuals with poorer thresholds in broadband noise and in random-frequency maskers were found to have stronger MOC reflexes.

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Figures

Figure 1
Figure 1
DPOAE fine structure in the no-CAS (red) and +CAS (blue) conditions for one adult subject.
Figure 2
Figure 2
Mean masked thresholds for broadband noise (BBN), fixed 4-tone complex (FIXED) and random 4-tone complex (RANDOM). Error bars represent one standard error of the mean.
Figure 3
Figure 3
Mean MOCR for single points measured below (MOCRLF) and above (MOCRHF) 1000-Hz. Error bars represent one standard error of the mean.
Figure 4
Figure 4
Mean MOCS in two frequency ranges. Error bars represent one standard error of the mean.
Figure 5
Figure 5
Scatterplot of MOCRLF as a function of masked threshold for the RANDOM condition.
Figure 6
Figure 6
Scatterplot of MOCS891 as a function of masked thresholds for BBN condition.
Figure 7
Figure 7
Mean MOCRLF and MOCRHF for low-threshold and high-threshold groups in three masking conditions
Figure 8
Figure 8
Mean MOCS891 and MOCS1122 for low- and high threshold groups in three masking conditions.
See this image and copyright information in PMC

References

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