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M. B. Jørgensen M. Kanneworff 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):59-64
The anuran middle ear serves to transmit eardrum vibrations to the inner ear. In order to do this efficiently, the eardrum
and middle ear must operate as an impedance transformer matching the low impedance of air to the higher impedance of the fluid-filled
inner ear. In amniotes, one of the mechanisms used to achieve impedance transformation is to have the middle ear work as a
force-amplifying lever system. Here, we present evidence that the grass frog middle ear also implements a lever system. The
columellar footplate, which sits in the oval window, is firmly connected to the otic capsule along its ventral edge. Therefore,
simple in-out movement of the columella is prevented while a rotational movement around the footplate's ventral edge is possible.
The latter movement pattern was confirmed by laser vibrometry measurements of eardrum and footplate vibrations. The results
showed that the footplate vibrations were 20–30 dB weaker than those of the eardrum and that the two structures vibrated 180°
out of phase (at low frequencies). The lever ratio was approximately 6, i.e. somewhat higher than lever ratios reported for
amniotes. Hence, the middle ear lever probably makes a significant contribution to impedance matching in frogs.
Accepted: 1 July 1997 相似文献
2.
J. Wang T. A. Ludwig P. M. Narins 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,178(2):159-172
We investigated directionalities of eardrum vibration and auditory nerve response in anesthetized northern leopard frogs (Rana pipiens pipiens). Simultaneous measures of eardrum velocities and firing rates from 282 auditory nerve fibers were obtained in response to free-field sounds from eight directions in the horizontal plane. Sound pressure at the external surface of the ipsilateral eardrum was kept constant for each presentation direction (± 0.5 dB). Significant effects of sound direction on eardrum velocity were shown in 90% of the cases. Maximum or minimum eardrum velocity was observed more often when sounds were presented from the lateral and posterior fields, or from the anterior and contralateral fields, respectively. Firing rates of 38% of the fibers were significantly affected by sound direction and maximum or minimum firing rate was observed more frequently when sounds were delivered from the lateral fields, or from the anterior and contralateral fields, respectively. Directionality patterns of eardrum velocity and nerve firing also vary with sound frequency. Statistically significant correlation between eardrum velocity and nerve fiber firing rate was demonstrated in only 45% of the fibers, suggesting that sound transmission to the inner ear through extratympanic pathways plays a non-trivial role in the genesis of directionality of auditory nerve responses.Abbreviations CF
characteristic frequency
- SVL
snout-vent length
- TM
tympanic membrane 相似文献
3.
A. P. Purgue 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(5):438-445
Members of the Rana catesbeiana clade display sexually dimorphic eardrums. In this species assemblage the eardrum of males can be 50% larger than in females
of the same body size. There has been, however, no apparent functional explanation for this dimorphism. Measurements of the
acoustical coupling (transfer function) of internally generated sound to the enlarged eardrum of male bullfrogs (R. catesbeiana) show distinct energy peaks coincident with those observed in the spectral envelopes of the release and mating calls. Moreover,
when the tympanic membranes are artificially damped the spectrum of the release call is drastically altered and the total
amount of power radiated decreases substantially. These observations point to a previously unsuspected role for the ears in
the sound broadcasting process of the bullfrog and possibly other anurans with similarly modified tympanic membranes.
Accepted: 19 July 1997 相似文献
4.
Calvin C. K. Ho Peter M. Narins 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2006,192(4):417-429
We studied the directional response of the coupled-eardrum system in the northern leopard frog, Rana pipiens pipiens. Eardrum behavior closely approximates a linear time-invariant system, with a highly correlated input–output relationship
between the eardrum pressure difference and the eardrum velocity. Variations in the eardrum transfer function at frequencies
below 800 Hz indicate the existence of an extratympanic sound transmission pathway which can interfere with eardrum motions.
The eardrum velocity was shown to shift in phase as a function of sound incident angle, which was a direct result of the phase-shift
of the eardrum pressure difference. We used two laser-Doppler vibrometers to measure the interaural vibration time difference
(IVTD) and the interaural vibration amplitude difference (IVAD) between the motions of the two eardrums. The coupled-eardrum
system enhanced the IVTD and IVAD by a factor of 3 and 3 dB, respectively, when compared to an isolated-eardrum system of
the same size. Our findings are consistent with the time-delay sensitivity of other coupled-eardrum systems such as those
found in crickets and flies. 相似文献
5.
Natasha Mhatre Fernando Montealegre-Z Rohini Balakrishnan Daniel Robert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(5):453-462
Crickets have two tympanal membranes on the tibiae of each foreleg. Among several field cricket species of the genus Gryllus (Gryllinae), the posterior tympanal membrane (PTM) is significantly larger than the anterior membrane (ATM). Laser Doppler
vibrometric measurements have shown that the smaller ATM does not respond as much as the PTM to sound. Hence the PTM has been
suggested to be the principal tympanal acoustic input to the auditory organ. In tree crickets (Oecanthinae), the ATM is slightly
larger than the PTM. Both membranes are structurally complex, presenting a series of transverse folds on their surface, which
are more pronounced on the ATM than on the PTM. The mechanical response of both membranes to acoustic stimulation was investigated
using microscanning laser Doppler vibrometry. Only a small portion of the membrane surface deflects in response to sound.
Both membranes exhibit similar frequency responses, and move out of phase with each other, producing compressions and rarefactions
of the tracheal volume backing the tympanum. Therefore, unlike field crickets, tree crickets may have four instead of two
functional tympanal membranes. This is interesting in the context of the outstanding question of the role of spiracular inputs
in the auditory system of tree crickets. 相似文献
6.
Morten Buhl Jørgensen Barbara Schmitz Jakob Christensen-Dalsgaard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(2):223-232
1. | We used laser vibrometry and free field sound stimulation to study the frequency responses of the eardrum and the lateral body wall of awake male Eleutherodactylus coqui. |
2. | The eardrum snowed one of two distinct frequency responses depending on whether the glottis was open (GO response) or closed (GC response) during the measurement. |
3. | The lateral body wall vibrated with a maximum amplitude close to that of the eardrum and in the same frequency range. |
4. | Covering the frog's body wall with vaseline reduced the vibration amplitude of the GC response by up to 15 dB. |
5. | When a closed sound delivery system was used to stimulate a local area of the body wall the eardrum also showed one of two types of responses. |
6. | These results suggest that sound is transmitted via the lung cavity to the internal surface of the eardrum. This lung input has a significant influence on the vibrations of the eardrum even when the glottis is closed. |
7. | The vibration amplitude of the eardrum changed with the angle of sound incidence. The directionality was most pronounced in a narrow frequency range between the two main frequencies of the conspecific advertisement call. |
7.
Morten Buhl Jørgensen H. Carl Gerhardt 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(2):177-183
1. We used laser vibrometry to study the vibrational frequency response of the eardrum of female gray tree frogs for different positions of the sound source in three-dimensional space. Furthermore, we studied the accuracy of 3-D phonotaxis in the same species for sounds with different frequency contents. 2. The directionality of the eardrum was most pronounced in a narrow frequency range between 1.3 and 1.8 kHz. 3. The average 3-D, horizontal and vertical jump error angles for phonotactic approaches with a sound similar to the natural advertisement call (1.1 and 2.2 kHz frequency components) were 23 degrees, 19 degrees and 12 degrees, respectively. 4. 3-D jump error angle distributions for the 1.4 + 2.2 kHz, 1.0 kHz and 2.0 kHz sounds were not significantly different from that for the 1.1 + 2.2 kHz sound. 5. The average 3-D jump error angle for the 1.4 kHz sound was 36 degrees, and the distribution was significantly different from that for the 1.1 + 2.2 kHz sound. Hence, phonotactic accuracy was poorer in the frequency range of maximum eardrum directionality. 6. Head scanning was not observed and is apparently unnecessary for accurate sound localization in three-dimensional space. 7. Changes in overall sound pressure level experienced by the frog during phonotactic approaches are not an important cue for sound localization. 相似文献
8.
Morten Buhl Jørgensen Jakob Christensen-Dalsgaard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):503-511
We studied the directionality of spike timing in the responses of single auditory nerve fibers of the grass frog, Rana temporaria, to tone burst stimulation. Both the latency of the first spike after stimulus onset and the preferred firing phase during
the stimulus were studied. In addition, the directionality of the phase of eardrum vibrations was measured. The response latency
showed systematic and statistically significant changes with sound direction at both low and high frequencies. The latency
changes were correlated with response strength (spike rate) changes and were probably the result of directional changes in
effective stimulus intensity. Systematic changes in the preferred firing phase were seen in all fibers that showed phaselocking
(i.e., at frequencies below 500–700 Hz). The mean phase lead for stimulation from the contralateral side was approximately
140° at 200 Hz and decreased to approximately 100° at 700 Hz. These phaseshifts correspond to differences in spike timing
of approximately 2 ms and 0.4 ms respectively. The phaseshifts were nearly independent of stimulus intensity. The phase directionality
of eardrum vibrations was smaller than that of the nerve fibers. Hence, the strong directional phaseshifts shown by the nerve
fibers probably reflect the directional characteristics of extratympanic pathways.
Accepted: 23 November 1996 相似文献
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