An extensive physiological literature, including experimental and clinical studies in humans, demonstrates that activation of the medial olivocochlear (MOC) efferent system, by either contralateral sound or electrical stimulation, can produce significant alterations in cochlear function and suggests a role for the MOC system in influencing the auditory behavior of binaural hearing. The present data are from psychophysical studies in nonhuman primates which seek to determine if the noted physiological changes in response to contralateral acoustic stimulation have a perceptual counterpart. Four juvenile Japanese macaques were trained to respond to the presence of 1-s sinusoids, presented to the test ear, in an operant reinforcement paradigm. Thresholds were compared for frequencies ranging from 1.0 to 4.0 kHz in quiet, with thresholds measured when continuous, two octave-band noise, centered on the test tone frequency, was presented in the contralateral ear. Contralateral noise was presented at levels of 10–60 dB above detection threshold for the test-tone frequency. While some variability was evident across subjects, both in the frequency distribution and magnitude (as a function of contralateral noise level), all subjects exhibited an increase, or suppression of thresholds in the presence of contralateral noise. On average, thresholds increased systematically with contralateral noise level, to a peak of 7 dB. In one subject, the threshold increase seen with contralateral noise was significantly reduced when the MOC was surgically sectioned on the floor of the IVth ventricle. The characteristics of the measured shifts in behavioral thresholds, in the presence of contralateral noise reported here, are qualitatively and quantitatively similar to both efferent physiological suppression effects and psychophysical central masking threshold shifts which have been reported previously. These data suggest that at least some aspects of “central masking” are efferent-mediated peripheral processes, and that the term “central masking” may be incorrect.

1.
Art
,
J. J.
,
Fettiplace
,
R.
, and
Fuchs
,
P. A.
(
1984
). “
Synaptic hyperpolarization and inhibition of turtle cochlear hair cells
,”
J. Physiol. (London)
356
,
525
550
.
2.
Benton
,
S. L.
, and
Sheeley
,
E. C.
(
1987
). “
Effects of three contralateral maskers on pure-tone thresholds using manual audiometry
,”
Audiology
26
,
227
234
.
3.
Blegvad
,
B.
(
1967
). “
Contralateral masking and Békésy audiometry in normal listeners
,”
Acta Oto-Laryngol.
64
,
157
165
.
4.
Brown
,
M. C.
, and
Nuttall
,
A. L.
(
1984
). “
Efferent control of cochlear inner hair cell responses in the guinea pig
,”
J. Physiol. (London)
354
,
625
646
.
5.
Brownell
,
W. E.
,
Bader
,
C. R.
,
Bertrand
,
D.
, and
Ribaupierre
,
Y.
(
1985
). “
Evoked mechanical response of isolated cochlear outer hair cells
,”
Science
227
,
194
196
.
6.
Buño
,
W.
(
1978
). “
Auditory nerve fiber activity influenced by contralateral ear sound stimulation
,”
Exp. Neurol.
59
,
62
74
.
7.
Collet
,
L.
,
Kemp
,
D. T.
,
Veuillet
,
E.
,
Duclaux
,
R.
,
Moulin
,
A.
, and
Morgan
,
A.
(
1990
). “
Effects of contralateral auditory on active cochlear micromechanical properties in human subjects
,”
Hear. Res.
43
,
251
262
.
8.
Dirks
,
D. D.
, and
Norris
,
J. C.
(
1966
). “
Shifts in auditory thresholds produced by ipsilateral and contralateral maskers at low-intensity levels
,”
J. Acoust. Soc. Am.
40
,
12
19
.
9.
Dirks
,
D.
, and
Malmquist
,
C.
(
1965
). “
Shifts in air conduction thresholds produced by pulsed and continuous contralateral maskers
,”
J. Acoust. Soc. Am.
37
,
631
.
10.
Dolan
,
D. F.
, and
Nuttall
,
A. L.
(
1988
). “
Masked cochlear whole-nerve response intensity functions altered by electrical stimulation of the crossed olivocochlear bundle
,”
J. Acoust. Soc. Am.
83
,
1081
1086
.
11.
Fex
,
J.
(
1967
). “
Efferent inhibition in the cochlea related to hair cell DC activity: Study of postsynaptic activity of the crossed olivocochlear fibers in the cat
,”
J. Acoust. Soc. Am.
41
,
666
675
.
12.
Flock
,
Å.
, and
Russell
,
I. J.
(
1976
). “
Inhibition of efferent nerve fibres, action on hair cells and afferent synaptic transmission in the lateral line canal of the burbot Lota lota,
J. Physiol. (London)
257
,
45
62
.
13.
Guinan
, Jr.,
J. J.
, and
Gifford
,
M. L.
(
1988
). “
Effects of electrical stimulation of efferent olivocochlear neurons on cat auditory-nerve fibers. III. Tuning curves and thresholds at CF
,”
Hear. Res.
37
,
29
46
.
14.
Guinan
, Jr.,
J. J.
,
Warr
,
W. B.
, and
Norris
,
B. E.
(
1984
). “
Topographic organization of the olivocochlear projections from lateral and medial zones of the superior olivary complex
,”
J. Comp. Neurol.
226
,
21
27
.
15.
Ingham
,
J. G.
(
1959
). “
Variations in cross-masking with frequency
,”
J. Exp. Psychol.
58
,
199
205
.
16.
Kawase
,
T.
,
Delgutte
,
B.
, and
Liberman
,
M. C.
(
1993
). “
Antimasking effects of the olivocochlear reflex. II. Enhancement of auditory-nerve response to masked tones
,”
J. Neurophysiol.
70
,
2533
2548
.
17.
Kawase
,
T.
, and
Liberman
,
M. C.
(
1993
). “
Antimasking effects of the olivocochlear reflex. I. Enhancement of compound action potentials to masked tones
,”
J. Neurophysiol.
70
,
2519
2532
.
18.
Kemp
,
D. T.
(
1978
). “
Stimulated acoustic emissions from the human auditory system
,”
J. Acoust. Soc. Am.
64
,
1386
1391
.
19.
Kemp
,
D. T.
, and
Chum
,
R.
(
1980
). “
Properties of the generator of stimulated acoustic emissions
,”
Hear. Res.
2
,
213
232
.
20.
Kemp
,
D. T.
, and
Souter
,
M.
(
1988
). “
A new rapid component in the cochlear response to brief electrical efferent stimulation
,”
Hear. Res.
34
,
49
62
.
21.
Konishi
,
T.
, and
Slepian
,
J. Z.
(
1970
). “
Effects of the electrical stimulation of the crossed-olivocochlear bundle on cochlear potentials recorded with intracochlear electrodes in guinea pigs
,”
J. Acoust. Soc. Am.
49
,
1762
1769
.
22.
Liberman
,
M. C.
(
1989
). “
Rapid assessment of sound-evoked olivocochlear feedback: Suppression of compound action potentials by contralateral sound
,”
Hear. Res.
38
,
47
56
.
23.
Liberman
,
M. C.
,
Dodd
,
L. W.
, and
Pierce
,
S.
(
1990
). “
Afferent and efferent innervation of the cochlea: Quantitative analysis with light and electron microscopy
,”
J. Comp. Neurol.
301
,
443
460
.
24.
Lidén
,
G.
,
Nilsson
,
G.
, and
Anderson
,
H.
(
1959
). “
Masking in clinical audiometry
,”
Acta Oto-Laryngol.
50
,
125
136
.
25.
Lima da Costa
,
D.
,
Chibois
,
A.
,
Erre
,
J.-P.
,
Blanchet
,
C.
,
Charlet de Sauvage
,
R.
, and
Aran
,
J.-M.
(
1997
). “
Fast, Slow and Steady-state effects of contralateral acoustic activation of the medial olivocochlear efferent system in awake guinea pigs: Action of gentamicin
,”
J. Neurophysiol.
78
,
1826
1836
.
26.
Madden
,
V. J.
, and
Henson
,
M. M.
(
1997
). “
Rapid decalcification of temporal bones with preservation of ultrastructure
,”
Hear. Res.
111
,
76
84
.
27.
Martin, F. N. (1972). Clinical Audiometry and Masking (Bobbs-Merrill, Indianapolis).
28.
Martin
,
F. N.
,
Bailey
, Jr.,
H. A. T.
, and
Pappas
,
J. J.
(
1962
). “
The effect of central masking on thresholds for speech
,”
J. Auditory Res.
5
,
293
.
29.
May
,
B. J.
, and
McQuone
,
S. J.
(
1995
). “
Effects of bilateral olivocochlear lesions on pure-tone intensity discrimination in cats
,”
Aud. Neurosci.
1
,
385
400
.
30.
Mott
,
J. B.
,
Norton
,
S. J.
,
Neely
,
S. T.
, and
Warr
,
W. B.
(
1989
). “
Changes in spontaneous otoacoustic emissions produced by acoustic stimulation of the contralateral ear
,”
Hear. Res.
38
,
229
242
.
31.
Mountain
,
D. C.
(
1980
). “
Changes in endolymphatic potential and crossed olivocochlear bundle stimulation alter cochlear mechanics
,”
Science
210
,
71
72
.
32.
Nieder
,
P.
, and
Nieder
,
I.
(
1970
). “
Crossed olivocochlear bundle: Electrical stimulation enhances masked neural responses to loud clicks
,”
Brain Res.
21
,
135
137
.
33.
Palva
,
L. L.
(
1954
). “
Masking in audiometry
,”
Acta Oto-Laryngol. Suppl.
118
,
156
.
34.
Pang, X. D., and Peake, W. T. (1986). “
How do contractions of the stapedius muscle alter the acoustic properties of the middle ear?” in Peripheral Auditory Mechanisms, edited by J. B. Allen, J. L. Hall, A. Hubbard, S. T. Neely, and A. Tubis (Springer-Verlag, New York), pp. 36–43
.
35.
Perry
,
B. P.
,
McSwain
,
S. D.
,
Conlon
,
B. J.
, and
Smith
,
D. W.
(
1999
). “
A comparison of efferent suppression of compound action potentials by simultaneous and non-simultaneous contralateral noise paradigms
,”
Audiology
38
,
1
6
.
36.
Probst
,
R.
,
Lonsbury-Martin
,
B. L.
, and
Martin
,
G. K.
(
1991
). “
A review of otoacoustic emissions
,”
J. Acoust. Soc. Am.
89
,
2027
2067
.
37.
Puria
,
S.
,
Guinan
,
J. J.
, and
Liberman
,
M. C.
(
1996
). “
Olivocochlear reflex assays: Effects of contralateral sound on compound action potentials versus ear-canal distortion products
,”
J. Acoust. Soc. Am.
99
,
500
507
.
38.
Rossi
,
G.
,
Actis
,
R
,
Solero
,
P.
,
Rolando
,
M.
, and
Pejrone
,
M. D.
(
1993
). “
Cochlear interdependence and micromechanics in Man and their relations with the activity of the medial olivocochlear efferent system (MOES)
,”
J. Laryngol. Otol.
107
,
883
891
.
39.
Sato
,
M.
,
Henson
,
M. M.
, and
Smith
,
D. W.
(
1997
). “
Normal synaptic morphology of outer hair cells in the organ of Corti of the Japanese Macaque
,”
Hear. Res.
108
,
46
54
.
40.
Scharf
,
B.
,
Magnan
,
J.
,
Collet
,
L.
,
Ulmer
,
E.
, and
Chays
,
A.
(
1994
). “
On the role of the olivocochlear bundle in hearing: A case study
,”
Hear. Res.
75
,
11
26
.
41.
Sherrick
,
C. E.
, and
Albernaz
,
P. L. M.
(
1961
). “
Auditory threshold shifts produced by pulsed contralateral stimuli
,”
J. Acoust. Soc. Am.
33
,
1381
1386
.
42.
Siegel
,
J. H.
, and
Kim
,
D. O.
(
1982
). “
Efferent neural control of cochlear mechanics? Olivocochlear bundle stimulation affects cochlear biomechanic non-linearity
,”
Hear. Res.
6
,
171
182
.
43.
Smith, D. W. (1998). “Effects of contralateral noise on absolute thresholds in non-human primates: Is “central masking” an efferent-mediated peripheral process?” in Psychophysical and Physiological Advances in Hearing, edited by A. R. Palmer, A. Rees, A. Q. Summerfield, and R. Medis (Whurr Publishers, London), pp. 26–33.
44.
Smith
,
D. W.
, and
Olszyk
,
V. B.
(
1997
). “
Auditory behavioral thresholds for Japanese macaques using insert earphones
,”
Am. J. Primatol.
41
,
323
329
.
45.
Smith
,
D. W.
,
Turner
,
D. A.
, and
Hensen
,
M. M.
(
1999
). “
The role of the medial olivocochlear efferent system in psychophysical ‘central masking’
,”
Abst. Assn. Res. Otolaryngol.
22
,
96
,
24
.
46.
Snyder
,
J. M.
(
1973
). “
Central masking in normal listeners
,”
Acta Oto-Laryngol.
75
,
419
424
.
47.
Sokolich, W. G. (1981). Closed sound delivery system, U.S. Patent 4,251,686.
48.
Strickland
,
E. A.
, and
Viemeister
,
N. F.
(
1995
). “
An attempt to find psychophysical evidence for efferent action in humans
,”
Abst. Assn. Res. Otolaryngol.
18
,
690
,
173
.
49.
Studebaker
,
G. A.
(
1964
). “
Clinical masking of air- and bone-conduction stimuli
,”
J. Speech Hear. Res.
29
,
32
.
50.
Studebaker
,
G. A.
(
1967
). “
Clinical masking of the non-test ear
,”
J. Speech Hearing Dis.
32
,
360
.
51.
Veuillet
,
E.
,
Collet
,
L.
, and
Duclaux
,
R.
(
1991
). “
Effect of contralateral auditory stimulation on active cochlear micro-mechanical properties in human subjects: Dependence on stimulus variables
,”
J. Neurophysiol.
65
,
724
735
.
52.
Warr, W. B., Guinan, J. J., and White, J. S. (1986). “Organization of the efferent fibers: The lateral and medial olivocochlear systems,” in Neurobiology of Hearing: The Cochlea, edited by R. A. Altschuler, D. W. Hoffman, and R. P. Bobbin (Raven, New York), pp. 333–348.
53.
Warren
III,
E. H.
, and
Liberman
,
M. C.
(
1989a
). “
Effects of contralateral sound on auditory nerve responses. I. Contributions of cochlear efferents
,”
Hear. Res.
37
,
89
104
.
54.
Warren
III,
E. H.
, and
Liberman
,
M. C.
(
1989b
). “
Effects of contralateral sound on auditory nerve responses. II. Dependence on stimulus variables
,”
Hear. Res.
37
,
105
122
.
55.
Wegel
,
R. L.
, and
Lane
,
C. E.
(
1924
). “
The auditory masking of one pure tone by another and its probable relations to the dynamics of the inner ear
,”
Phys. Rev.
23
,
266
285
.
56.
Wiederhold
,
M. L.
, and
Kiang
,
N. Y. S.
(
1970
). “
Effects of electrical stimulation of the crossed olivocochlear bundle on single auditory-nerve fibers in the cat
,”
J. Acoust. Soc. Am.
48
,
950
965
.
57.
Williams
,
D. M.
, and
Brown
,
A. M.
(
1995
). “
Contralateral and ipsilateral suppression of the 2f1−f2 distortion product in human subjects
,”
J. Acoust. Soc. Am.
97
,
1130
1140
.
58.
Williams
,
E. A.
,
Brookes
,
G. B.
, and
Prasher
,
D. K.
(
1993
). “
Effects of contralateral acoustic stimulation on otoacoustic emissions following vestibular neurectomy
,”
Scand. Audiol.
22
,
197
203
.
59.
Winslow
,
R. L.
, and
Sachs
,
M. B.
(
1987
). “
Effect of electrical stimulation of the crossed olivocochlear bundle on auditory nerve response to tones in noise
,”
J. Neurophysiol.
57
,
1002
1021
.
60.
Zwislocki
,
J. J.
(
1971
). “
Central masking and neural activity in the cochlear nucleus
,”
Audiology
10
,
48
59
.
61.
Zwislocki
,
J. J.
,
Buining
,
E.
, and
Glantz
,
J.
(
1968
). “
Frequency distribution of central masking
,”
J. Acoust. Soc. Am.
4
,
1267
1271
.
62.
Zwislocki
,
J. J.
,
Damianopoulos
,
E. N.
,
Buining
,
E.
, and
Glantz
,
J.
(
1967
). “
Central masking: Some steady-state and transient effects
,”
Percept. Psychophys.
2
,
59
64
.
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