Aberrant tonotopic organization in the inner ear damaged by kanamycin D. Robedson
and B. M. Johnstone
Departmentof Physiology,Universityof WesternAustralia, Nedlands.6009, WesternAustralia
(Received28 December1978;acceptedfor publication26 April 1979)
Spiralganglioncell recordings wereobtainedfrom normaland kanamycin-damaged guineapig cochleas. Resultsshowthat kanamycinpoisoning, whichcauseslossof outerhair cells,leadsto a lossof sharp, sensitive tuningand,in addition,a shiftto lowerfrequencies in the tuningcurvesfrom a damagedregion. The normaltonopticpatternof organization is thereforegreatlydisrupted in the damaged cochleas. PACS numbers: 43.63.La, 43.63.Pd, 43.63.Gw
INTRODUCTION
sisted of 8-10 days subcutaneous injection according to
The neural output of the mammalian cochlea is organized tonotopically, inthat nerve fibers emanating from a given region of the organ of Corti are most sensitive to a particular frequency of acoustic stimulation. This
most sensitive or characteristic frequency (CF)varies in orderly fashion from the base of the cochlear spiral to the apex, the base subserving high and the apex low frequencies. The most direct,
and probably the most accurate
"place-frequency" maps of the neural output have been obtained for the basal coil of the guinea pig cochlea,
usingthe techniqueof spiral ganglionrecording. l's With this method the electrical activity of single primary afferent neurons is measured only about 400 p m from the organ of Corti. If a simple radial pattern of innervation
is assumed,4 the cf of a givenneuroncanbe directly related to the receptor location it presumably inner-
the procedureof Dallos and coworkersf Animalswere kept for 10-27 days after the final injection before acute experimentation. In the second schedule, approximately 10 mg of solid kanamycin sulfate was placed in the round window niche using sterile surgical techniques. Survival times ranged from 9 to 17 days. This latter method did not give reliable outer hair-cell loss in all animals.
Assessment of hair-cell loss in the basal coil was by scanning electronmicroscopy, using techniques similar
to thosereportedby Hunter-Duvar.7 The organof Corti locations opposite spiral ganglion recording sites were marked with small dabs of enamel paint which were readily visible in the scanning microscope. In this way, neural recording sites could be directly related to specific regions on the organ of Corti.
vates.
II.
In this communication, we examine the "place-frequency" relationship in cochleas poisoned with kanamycin,
neurons.
a drug which selectively destroys the outer hair cells of the organ of Corti. The results show that neurons emanating from damaged receptor regions are often most sensitive to quite inappropriate frequencies.
the guineapig havebeenpublishedpreviously? In the present study, extracellular recordings of spike activity were obtained using glass micropipettes filled with 150
mmol/1 NaC1. A neuron's cf was estimated from its tuning curve (a plot of threshold sound-pressure level versus stimulation frequency). A calibrated sound delivery system identical to that employed by WilSon and Johnstone5 was used. data were obtained from young, healthy
guinea pigs (150-350 g). Scanning electron microscopicof the basal
coil
revealed
at most
two or
three outer hair cells missing from the first 6 mm of the organ of Corti in these control animals. Damaged cochleas were produced by one of two schedules of kanamycin sulfate administration. The first con466
The CF of these neurons
showed an orderly distance
from
in normal
cochleas
dependence on location measured as
the basal
end of the basilar
membrane.
Examples of typical ganglion cell tuning curves are shown in Fig. I and the relationship between cf and distance in Fig. 2. These neurons had CFs ranging from from
The essential details of surgical and recording procedures used to record from spiral ganglion neurons in
al examination
Normative data were obtained from 59 spiral ganglion
11-30 kHz encompassing locations on the organ of Corti
I. METHODS
Normative
RESULTS
J. Acoust.Soc.Am. 66(2), Aug. 1979
4.8-1.7
mm from
its basal
end.
For
all these
neurons, threshold sensitivity at the cf was better than 40 dB.
These results agreed quite well with previous record-
ingsfrom the spiral ganglion. l's They showa linear relationship between log (CF) and linear distance, which has a slope of 2.5 mm/octave. This relationship agrees very well with the location of the cutoff frequencies of the basilar membrane mechanical tuning curves reported
by Wilson andJohnstone 5 for the basal coil of the guinea pig cochlea (dotted line in Fig. 2). The results from kanamycin-poisoned animals were markedly different. Single neurons emanating from regions with totally absent outer hair cells (Fig. 3) showed very broad, insensitive tuning curves. The most sensitive high-frequency portion of the curves were elevated by some 40 dB compared to neurons from the same location
in normal
0001-4966/79/080466-04500.80
cochleas.
Elevations
of threshold
(D1979 Acoustical Societyof America
on
466
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
IHC
I 4
5
6
7
8
910
,
20
30
FREQUENCY, kHz
FIG. 1. Representative single neuron tuning curves from three separate cochlear locations. Solid curves are from normal guinea pigs. Dashed curves are from the same locations
FIG. 3. Scanning electron micrographs of A; normal organ of Corti, and B. kanamycin-damaged organ of Corti. IHC- inner hair cell region, OHC- outer hair cell region. Note absence
but in animals devoid of outer hair cells in these regions. Dis-
of outer
rance
in mm from
basal
end of basilar
membrane
is denoted
hair
cell
stereocilia
in B.
on
ß
left-hand side of each group.
the tails of tuning curves were less; of the order of 1020 dB. This finding is in rough agreement with reports
by other workers, •-10who havefoundelevationof tuning [
[
I
1
30--
_
curve tips and broad tuning curves from kanamycinpoisoned cochleas when single neuron activity is recorded
from
the cochlear
nerve
trunk.
However, perhaps most significant was that the CFs of the neurons were shifted to frequencies up to 1 octave
lower than normal for their location (Fig. 2, Closed circles).
Many of these neurons were so broadly tuned
that the assignment of a CF was somewhat arbitrary. Nevertheless, the high-frequency cutoffs of the neurons were also dramatically shifted to lower frequencies than
normal (Fig. 4). mm
from
basal
end
FIG. 2. Relationship between single ganglion cell C F and location of the radial projection of ganglion recording hole to the organ of Corti. Open circles; units from normal animals. Closed circles; units from regions devoid of outer hair cells in kanamycin treated guinea pigs. Dotted line is relationship between location and cutoff frequency of the basilar membrane
mechanicaltuningcurve.5 467
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
Neurons from these kanamycin-damaged cochleas which arose from undamaged receptor regions, showed
tuning curves more •{early approachingnormal shape
andsensitivity. Suchneuronsalso had•Fs closer to, or in exact agreement with, the normal CF for their location (Fig. 4.) These results clearly show that outer hair-cell loss resulting in threshold changes of 40 dB or more can be D. Robertsonand B. M. Johnstone:Tonotopicorganization
467
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
4
6
8
10
20
30
incorrect conclusions about the relationship between cochlear receptor damage and single neuron response.
100r_l I I I I I I ' ' ''1''"l"'"""l A
Our findings are, in principle,
in accordance with the
8O
statementby Kiang, Liberman, and Levinetø;"If there
6O
cells, there will be a gap in the range of assignable
is a region in the cochlea which is devoid of outer hair
90r' B
CF." It seems from our data that this is probably due
I,•
to neurons from the outer hair cell-damaged region shifting their CF to a lower frequency, and not to a physical absence of responsiveness on the part of these auditory afferents.
70
6O
It is perhaps debatable whether the phenomenonwe observe actually constitutes a "CF shift" in the strict sense of the term. Some authors have reported neurons which do tune to frequencies encompassed by regions devoid of outer hair cells. 8'tt Dallos and Harris tt in
% hair cell •HC present
100 0
6
5 4 3 mm from basal
2 end
chinchilla cochleas found tuning curves apparently
from such regions, which still possessedsharp tuning
D
tips, though greatly elevated in threshold and much reduced in depth. We have never found such units and in this respect our results are in closer agreement with
70
thoseof Kiang, Liberman, and Levine.9'tø Possibly what we observe is simply the residual low-frequency portion of the tuning curve with the tip completely missing. However, recent data from our laboratory (V. A. Alder, unpublished results; A. R. Cody, unpublished
50
results) strongly imply that there is a graded shift of 4
6
8
10
20
30
FREQUENCY, kHz
FIG. 4. Tuning curves from three spiral ganglion locations in a kanamyein-poisoned animal. A and B are from regions with missing outer hair cells, D from an undamagedregion. Pattern of hair-cell
loss shown in C.
Distance
in C has been
aligned with the frequency axes of A, B, and D according to the normal data shown in Fig. 2.
associated
with
a dramatic
shift
in the CF of neurons
emanating from these damaged regions. III.
DISCUSSION
The above results have far-reaching implications for studies on cochlear pathology. All previous recordings of single neuron activity from cochleas with hair cell loss have been obtained
from
the cochlear
nerve
trunk
in
the internalauditorymeatus.8'tt In thesestudies,the region from which a neuron emanates has to be inferred
from its CF and the place-frequency map of the normal
cochlea. • AsKiang,Liberman,andLevine tønote;"Any correlation of auditory physiology with cochlear histology is based on the premise that the CF dimension in the
auditory nerve maps in some continuousway onto the • longitudinal dimension of the cochlea."
Our results show
that the map may.be different in the normal and abnormal cochlea and that the only way to draw conclusions with certainty is to use a direct method of relating unit activity to location as we have done. For example, a unit whose CF is shifted from 18 to 12 kHz might be supposed to arise from a point 4.7 mm from the end of the basilar membrane when in fact it may actually innervate the 3.2-mm point. Such gross discrepancies could lead to
the CF to lower frequencies, accompanying threshold elevation, rather than a simple upward elevation and subsequent disappearance of the tuning tip. The discrepancy between our results and those of
DallosandHarristt mightbe explainedby partial inner hair-cell
damage in our animals,
for which we have
some ultrastructural evidence (Robertson, unpublished results). This, however, does not alter the basic point; that assigning a cochlear location to auditory afferents, solely on the bases of CF or high-frequency cutoff may be a risky procedure and could introduce errors of up to one octave. Future studies aimed at correlating receptor damage with changes in neural output, must take into account such alterations in tonotopic organization as we have demonstrated. We also feel our results may be important for understanding disturbances of hearing function in sensorineural deafness. If auditory neurons from regions with hair-cell damage are not only elevated in threshold but have their tuning curves shifted as we have found, then the ability of higher brain centers to frequency analyze incoming information must surely be greatly impaired. This impairment would be in addition to that which may be caused by any broadening of the tuning curve and loss of sensitivity. Other authors have previously drawn attention to this possibility that the presence of abnormal responses may be more detrimental than a complete abt0 sence of responsiveness. ACKNOWLEDGMENTS
This work was supported by a grant to B. M. J. from the Australian
Research
a Queen Elizabeth
Grants
II Fellow.
Commission.
D. R. was
The authors wish to
,
468
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
D. Robertsonand B. M. Johnstone' Tonotopic organization
468
.
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
acknowledge the participation of A. R. Cody in several experiments, and J. R. Johnstone for helpful discussion.
probe," J. Acoust. Soc. Am. 57, 705 (1975).
6P.Dallos, M. C. ]3illone,J. D. Durrant, C-Y. Wang, and S. Raynor,
"Cochlear
differences,"
inner and outer hair cells:
Functional
Science 177, 356 (1972).
7I. M. Hunter-Duvar, "Electronmicroscopicassessmentof the cochlea," Acta Oto. Larymgol. Suppl. 351 (1978).
1j. R. Johnstone,"Properties of ganglioncells from the extreme basal region of guinea pig cochlea," in Psycholvhysics and PhyMology of Hearing, edited by E. F. Evans and J.P. Wilson (Academic, New York, 1977), pp. 89-98.
2D. Robertson,"Studiesof singleneuronactivity in the cochlear ganglion of the guinea pig," Ph.D. thesis, McGill University, Montreal, 1975.
3D.RobertsonandG. A. Manley, 'Wianipulation of frequency analysis in the cochlear ganglion of the guinea pig, "J. Comp. Physiol. 91, 363 (1974).
4H.Spoendlin,"Innerrationdensitiesof the cochlea," Acta Oto. Laryngol. 73, 235 (1972).
•J. P. WilsonandJ• R. Johnstone,"Basilar membraneand middle ear vibration in guinea pig measured by capacitive
469
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
BE.F. EvansandR. V. Harrison,"Correlationbetweencochlear outer hair cell damage and deterioration of cochlear nerve fibre tuning properties in the guinea pig," J. Physiol. London, 256, 43P (1976).
'+N.Y.S.Kiang, E. C. Moxon,andR. A. Levine, "Auditory nerve activity in cats with normal and abnormal cochleas," in Sensorineural Hearing Loss, edited by G. E. W. Wolsten-
holme and J. Knight (Churchill, London, 1970), pp. 241-273.'
løN.Y. S Kiang, M. C. Liberman,andR. A. Levine, "Auditory nerve activity in cats exposed to ototoxic drugs and high intensity sounds," Ann. Otol. Rhino. Laryngol. 75, 752 (1976).
l•P. DallosandD. Harris, "Propertiesof auditorynerveresponses in absence of outer hair cells," J. Neurophysiol. 41, 365 (1978).
D. RobertsonandB. M. Johnstone:Tonotopicorganization
469
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
and B. M. Johnstone
Departmentof Physiology,Universityof WesternAustralia, Nedlands.6009, WesternAustralia
(Received28 December1978;acceptedfor publication26 April 1979)
Spiralganglioncell recordings wereobtainedfrom normaland kanamycin-damaged guineapig cochleas. Resultsshowthat kanamycinpoisoning, whichcauseslossof outerhair cells,leadsto a lossof sharp, sensitive tuningand,in addition,a shiftto lowerfrequencies in the tuningcurvesfrom a damagedregion. The normaltonopticpatternof organization is thereforegreatlydisrupted in the damaged cochleas. PACS numbers: 43.63.La, 43.63.Pd, 43.63.Gw
INTRODUCTION
sisted of 8-10 days subcutaneous injection according to
The neural output of the mammalian cochlea is organized tonotopically, inthat nerve fibers emanating from a given region of the organ of Corti are most sensitive to a particular frequency of acoustic stimulation. This
most sensitive or characteristic frequency (CF)varies in orderly fashion from the base of the cochlear spiral to the apex, the base subserving high and the apex low frequencies. The most direct,
and probably the most accurate
"place-frequency" maps of the neural output have been obtained for the basal coil of the guinea pig cochlea,
usingthe techniqueof spiral ganglionrecording. l's With this method the electrical activity of single primary afferent neurons is measured only about 400 p m from the organ of Corti. If a simple radial pattern of innervation
is assumed,4 the cf of a givenneuroncanbe directly related to the receptor location it presumably inner-
the procedureof Dallos and coworkersf Animalswere kept for 10-27 days after the final injection before acute experimentation. In the second schedule, approximately 10 mg of solid kanamycin sulfate was placed in the round window niche using sterile surgical techniques. Survival times ranged from 9 to 17 days. This latter method did not give reliable outer hair-cell loss in all animals.
Assessment of hair-cell loss in the basal coil was by scanning electronmicroscopy, using techniques similar
to thosereportedby Hunter-Duvar.7 The organof Corti locations opposite spiral ganglion recording sites were marked with small dabs of enamel paint which were readily visible in the scanning microscope. In this way, neural recording sites could be directly related to specific regions on the organ of Corti.
vates.
II.
In this communication, we examine the "place-frequency" relationship in cochleas poisoned with kanamycin,
neurons.
a drug which selectively destroys the outer hair cells of the organ of Corti. The results show that neurons emanating from damaged receptor regions are often most sensitive to quite inappropriate frequencies.
the guineapig havebeenpublishedpreviously? In the present study, extracellular recordings of spike activity were obtained using glass micropipettes filled with 150
mmol/1 NaC1. A neuron's cf was estimated from its tuning curve (a plot of threshold sound-pressure level versus stimulation frequency). A calibrated sound delivery system identical to that employed by WilSon and Johnstone5 was used. data were obtained from young, healthy
guinea pigs (150-350 g). Scanning electron microscopicof the basal
coil
revealed
at most
two or
three outer hair cells missing from the first 6 mm of the organ of Corti in these control animals. Damaged cochleas were produced by one of two schedules of kanamycin sulfate administration. The first con466
The CF of these neurons
showed an orderly distance
from
in normal
cochleas
dependence on location measured as
the basal
end of the basilar
membrane.
Examples of typical ganglion cell tuning curves are shown in Fig. I and the relationship between cf and distance in Fig. 2. These neurons had CFs ranging from from
The essential details of surgical and recording procedures used to record from spiral ganglion neurons in
al examination
Normative data were obtained from 59 spiral ganglion
11-30 kHz encompassing locations on the organ of Corti
I. METHODS
Normative
RESULTS
J. Acoust.Soc.Am. 66(2), Aug. 1979
4.8-1.7
mm from
its basal
end.
For
all these
neurons, threshold sensitivity at the cf was better than 40 dB.
These results agreed quite well with previous record-
ingsfrom the spiral ganglion. l's They showa linear relationship between log (CF) and linear distance, which has a slope of 2.5 mm/octave. This relationship agrees very well with the location of the cutoff frequencies of the basilar membrane mechanical tuning curves reported
by Wilson andJohnstone 5 for the basal coil of the guinea pig cochlea (dotted line in Fig. 2). The results from kanamycin-poisoned animals were markedly different. Single neurons emanating from regions with totally absent outer hair cells (Fig. 3) showed very broad, insensitive tuning curves. The most sensitive high-frequency portion of the curves were elevated by some 40 dB compared to neurons from the same location
in normal
0001-4966/79/080466-04500.80
cochleas.
Elevations
of threshold
(D1979 Acoustical Societyof America
on
466
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
IHC
I 4
5
6
7
8
910
,
20
30
FREQUENCY, kHz
FIG. 1. Representative single neuron tuning curves from three separate cochlear locations. Solid curves are from normal guinea pigs. Dashed curves are from the same locations
FIG. 3. Scanning electron micrographs of A; normal organ of Corti, and B. kanamycin-damaged organ of Corti. IHC- inner hair cell region, OHC- outer hair cell region. Note absence
but in animals devoid of outer hair cells in these regions. Dis-
of outer
rance
in mm from
basal
end of basilar
membrane
is denoted
hair
cell
stereocilia
in B.
on
ß
left-hand side of each group.
the tails of tuning curves were less; of the order of 1020 dB. This finding is in rough agreement with reports
by other workers, •-10who havefoundelevationof tuning [
[
I
1
30--
_
curve tips and broad tuning curves from kanamycinpoisoned cochleas when single neuron activity is recorded
from
the cochlear
nerve
trunk.
However, perhaps most significant was that the CFs of the neurons were shifted to frequencies up to 1 octave
lower than normal for their location (Fig. 2, Closed circles).
Many of these neurons were so broadly tuned
that the assignment of a CF was somewhat arbitrary. Nevertheless, the high-frequency cutoffs of the neurons were also dramatically shifted to lower frequencies than
normal (Fig. 4). mm
from
basal
end
FIG. 2. Relationship between single ganglion cell C F and location of the radial projection of ganglion recording hole to the organ of Corti. Open circles; units from normal animals. Closed circles; units from regions devoid of outer hair cells in kanamycin treated guinea pigs. Dotted line is relationship between location and cutoff frequency of the basilar membrane
mechanicaltuningcurve.5 467
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
Neurons from these kanamycin-damaged cochleas which arose from undamaged receptor regions, showed
tuning curves more •{early approachingnormal shape
andsensitivity. Suchneuronsalso had•Fs closer to, or in exact agreement with, the normal CF for their location (Fig. 4.) These results clearly show that outer hair-cell loss resulting in threshold changes of 40 dB or more can be D. Robertsonand B. M. Johnstone:Tonotopicorganization
467
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
4
6
8
10
20
30
incorrect conclusions about the relationship between cochlear receptor damage and single neuron response.
100r_l I I I I I I ' ' ''1''"l"'"""l A
Our findings are, in principle,
in accordance with the
8O
statementby Kiang, Liberman, and Levinetø;"If there
6O
cells, there will be a gap in the range of assignable
is a region in the cochlea which is devoid of outer hair
90r' B
CF." It seems from our data that this is probably due
I,•
to neurons from the outer hair cell-damaged region shifting their CF to a lower frequency, and not to a physical absence of responsiveness on the part of these auditory afferents.
70
6O
It is perhaps debatable whether the phenomenonwe observe actually constitutes a "CF shift" in the strict sense of the term. Some authors have reported neurons which do tune to frequencies encompassed by regions devoid of outer hair cells. 8'tt Dallos and Harris tt in
% hair cell •HC present
100 0
6
5 4 3 mm from basal
2 end
chinchilla cochleas found tuning curves apparently
from such regions, which still possessedsharp tuning
D
tips, though greatly elevated in threshold and much reduced in depth. We have never found such units and in this respect our results are in closer agreement with
70
thoseof Kiang, Liberman, and Levine.9'tø Possibly what we observe is simply the residual low-frequency portion of the tuning curve with the tip completely missing. However, recent data from our laboratory (V. A. Alder, unpublished results; A. R. Cody, unpublished
50
results) strongly imply that there is a graded shift of 4
6
8
10
20
30
FREQUENCY, kHz
FIG. 4. Tuning curves from three spiral ganglion locations in a kanamyein-poisoned animal. A and B are from regions with missing outer hair cells, D from an undamagedregion. Pattern of hair-cell
loss shown in C.
Distance
in C has been
aligned with the frequency axes of A, B, and D according to the normal data shown in Fig. 2.
associated
with
a dramatic
shift
in the CF of neurons
emanating from these damaged regions. III.
DISCUSSION
The above results have far-reaching implications for studies on cochlear pathology. All previous recordings of single neuron activity from cochleas with hair cell loss have been obtained
from
the cochlear
nerve
trunk
in
the internalauditorymeatus.8'tt In thesestudies,the region from which a neuron emanates has to be inferred
from its CF and the place-frequency map of the normal
cochlea. • AsKiang,Liberman,andLevine tønote;"Any correlation of auditory physiology with cochlear histology is based on the premise that the CF dimension in the
auditory nerve maps in some continuousway onto the • longitudinal dimension of the cochlea."
Our results show
that the map may.be different in the normal and abnormal cochlea and that the only way to draw conclusions with certainty is to use a direct method of relating unit activity to location as we have done. For example, a unit whose CF is shifted from 18 to 12 kHz might be supposed to arise from a point 4.7 mm from the end of the basilar membrane when in fact it may actually innervate the 3.2-mm point. Such gross discrepancies could lead to
the CF to lower frequencies, accompanying threshold elevation, rather than a simple upward elevation and subsequent disappearance of the tuning tip. The discrepancy between our results and those of
DallosandHarristt mightbe explainedby partial inner hair-cell
damage in our animals,
for which we have
some ultrastructural evidence (Robertson, unpublished results). This, however, does not alter the basic point; that assigning a cochlear location to auditory afferents, solely on the bases of CF or high-frequency cutoff may be a risky procedure and could introduce errors of up to one octave. Future studies aimed at correlating receptor damage with changes in neural output, must take into account such alterations in tonotopic organization as we have demonstrated. We also feel our results may be important for understanding disturbances of hearing function in sensorineural deafness. If auditory neurons from regions with hair-cell damage are not only elevated in threshold but have their tuning curves shifted as we have found, then the ability of higher brain centers to frequency analyze incoming information must surely be greatly impaired. This impairment would be in addition to that which may be caused by any broadening of the tuning curve and loss of sensitivity. Other authors have previously drawn attention to this possibility that the presence of abnormal responses may be more detrimental than a complete abt0 sence of responsiveness. ACKNOWLEDGMENTS
This work was supported by a grant to B. M. J. from the Australian
Research
a Queen Elizabeth
Grants
II Fellow.
Commission.
D. R. was
The authors wish to
,
468
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
D. Robertsonand B. M. Johnstone' Tonotopic organization
468
.
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
acknowledge the participation of A. R. Cody in several experiments, and J. R. Johnstone for helpful discussion.
probe," J. Acoust. Soc. Am. 57, 705 (1975).
6P.Dallos, M. C. ]3illone,J. D. Durrant, C-Y. Wang, and S. Raynor,
"Cochlear
differences,"
inner and outer hair cells:
Functional
Science 177, 356 (1972).
7I. M. Hunter-Duvar, "Electronmicroscopicassessmentof the cochlea," Acta Oto. Larymgol. Suppl. 351 (1978).
1j. R. Johnstone,"Properties of ganglioncells from the extreme basal region of guinea pig cochlea," in Psycholvhysics and PhyMology of Hearing, edited by E. F. Evans and J.P. Wilson (Academic, New York, 1977), pp. 89-98.
2D. Robertson,"Studiesof singleneuronactivity in the cochlear ganglion of the guinea pig," Ph.D. thesis, McGill University, Montreal, 1975.
3D.RobertsonandG. A. Manley, 'Wianipulation of frequency analysis in the cochlear ganglion of the guinea pig, "J. Comp. Physiol. 91, 363 (1974).
4H.Spoendlin,"Innerrationdensitiesof the cochlea," Acta Oto. Laryngol. 73, 235 (1972).
•J. P. WilsonandJ• R. Johnstone,"Basilar membraneand middle ear vibration in guinea pig measured by capacitive
469
J. Acoust.Soc.Am., Vol. 66, No. 2, August1979
BE.F. EvansandR. V. Harrison,"Correlationbetweencochlear outer hair cell damage and deterioration of cochlear nerve fibre tuning properties in the guinea pig," J. Physiol. London, 256, 43P (1976).
'+N.Y.S.Kiang, E. C. Moxon,andR. A. Levine, "Auditory nerve activity in cats with normal and abnormal cochleas," in Sensorineural Hearing Loss, edited by G. E. W. Wolsten-
holme and J. Knight (Churchill, London, 1970), pp. 241-273.'
løN.Y. S Kiang, M. C. Liberman,andR. A. Levine, "Auditory nerve activity in cats exposed to ototoxic drugs and high intensity sounds," Ann. Otol. Rhino. Laryngol. 75, 752 (1976).
l•P. DallosandD. Harris, "Propertiesof auditorynerveresponses in absence of outer hair cells," J. Neurophysiol. 41, 365 (1978).
D. RobertsonandB. M. Johnstone:Tonotopicorganization
469
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 129.174.21.5 On: Sat, 20 Dec 2014 01:27:21
