Summary
-
1.
Absolute thresholds to tone and noise bursts were measured for 177 single auditory fibers in the eighth nerves of 8 adult green treefrogs (Hyla cinerea). The lowest tonal thresholds were found between 300 and 600 Hz (at about 30 dB SPL) and lowest noise thresholds between 500 and 1,200 Hz (at about 10 dB spectrum level, noise bandwidth 20–10,000 Hz).
-
2.
Masking effects of continuous broad-band noise on the response to tone bursts were studied using rate-intensity and latency-intensity curves and PST-histograms. The dynamics of masking can be described by two noise levels, one at which a fiber starts responding to background noise (in the presence of tone bursts), and the other at which the response of a fiber is totally dominated by noise (the response to the tone bursts is masked). This ‘dynamic range of masking’ varies around 20 dB measured in rateintensity curves and around 10 dB in latency-intensity curves.
-
3.
The fibers are divided into four response types according to their response rate change in the masking paradigm. The differences can be explained by different influences of summation, adaptation and suppression in the four groups of fibers.
-
4.
Masked thresholds of the fibers were used for calculation of the masking susceptibility, which is equal to the bandwidth of the critical ratio (CR-band) filter of a fiber. Fibers with best excitatory frequencies (BEFs) below 700 Hz have CR-bandwidths mostly between 10 and 100 Hz, those with higher BEFs have CR-bands mostly between 50 and 1,000 Hz. CR-bands were found in nerve fibers originating in both hearing organs (amphibian and basilar papilla) in treefrogs.
-
5.
The neural CR-bandwidths are significantly related to the sharpness of tuning (Q10-values) and they agree well with the 3 dB bandwidths of the tuning curves of the respective fibers.
-
6.
The mean neural CR-bandwidths near 900 and 3,000 Hz mid-frequency are very similar to those behaviorally measured at these frequencies. This similarity suggests that the mechanism of the CR-band (critical band) filter is of peripheral origin and may be identical with the filtering process leading to the frequency tuning curve of a single fiber in the auditory nerve.
Similar content being viewed by others
Abbreviations
- BEF:
-
best excitatory frequency
- CR-band :
-
critical ratio band
- PST-histogram :
-
post-stimulus-time histogram
- SPL :
-
sound pressure level
References
Capranica RR (1976) Morphology and physiology of the auditory systems. In: Llinás R, Precht W (eds) Frog neurobiology. Springer, Berlin Heidelberg New York, pp 551–575
Capranica RR (1977) Auditory processing of vocal signals in anurans. In: Taylor DH, Guttman SI (eds) The reproductive biology of Amphibians. Plenum Press, New York London, pp 337–355
Ehret G (1975) Masked auditory thresholds, critical ratios, and scales of the basilar membrane of the house mouse (Mus musculus). J Comp Physiol 103:329–341
Ehret G, Gerhardt HC (1980) Auditory masking and effects of noise on responses of the green treefrog (Hyla cinerea) to synthetic mating calls. J Comp Physiol 141:13–18
Evans EF (1974) Auditory frequency selectivity and the cochlear nerve. In: Zwicker E, Terhardt E (eds) Facts and models in hearing. Springer, Berlin Heidelberg New York, pp 118–129
Evans EF (1975) Cochlear nerve and cochlear nucleus. In: Keidel WD, Neff WD (eds) Handbook of sensory physiology, vol V/2. Springer, Berlin Heidelberg New York, pp 1–108
Evans EF, Wilson JP (1973) The frequency selectivity of the cochlea. In: Møller AR (ed) Basic mechanisms in hearing. Academic Press, New York London, pp 519–551
Evans EF, Rosenberg J, Wilson JP (1970) The effective bandwidth of cochlear nerve fibers. J Physiol (London) 207:62–63 P
Fay RR (1974) Masking of tones by noise for the goldfish (Carassius auratus). J Comp Physiol Psychol 87:708–716
Feng AS, Narins PM, Capranica RR (1975) Three populations of primary auditory fibers in the bullfrog (Rana catesbeiana): Their pheripheral origins and frequency sensitivities. J Comp Physiol 100:221–229
Fletcher H (1940) Auditory patterns. Rev Mod Phys 12:47–65
Gerhardt HC (1974) The significance of some spectral features in mating call recognition in the green treefrog (Hyla cinerea). J Exp Biol 61:229–241
Gerhardt HC (1976) Significance of two frequency bands in long distance vocal communication in the green treefrog. Nature 261:692–694
Goldberg JM, Greenwood DD (1966) Response of the neurons of the dorsal and posteroventral cochlear nuclei of the cat to acoustic stimuli of long duration. J Neurophysiol 29:72–93
Greenwood DD, Goldberg JM (1970) Response of neurons in the cochlear nuclei to variations in noise bandwidth and to tone-noise combinations. J Acoust Soc Am 47:1022–1040
Kiang NYS, Watenabe T, Thomas EC, Clark LF (1965) Discharge patterns of single fibers in the cat's auditory nerve. Res Monograph No 35. M.I.T. Press, Cambridge
Liff HJ, Goldstein MH (1970) Peripheral inhibition in auditory fibers in the frog. J Acoust Soc Am 47:1538–1547
Markl H, Ehret G (1973) Die Hörschwelle der Maus (Mus musculus). Eine kritische Wertung der Methoden zur Bestimmung der Hörschwelle eines Säugetieres. Z Tierpsychol 33:274–286
Moffat AJM, Capranica RR (1974) Sensory processing in the peripheral auditory system of treefrogs (Hyla). J Acoust Soc Am 55:480
Möller J, Neuweiler G, Zöller H (1978) Response characteristics of inferior colliculus neurons of the awake CF-FM batRhinolophus ferrumequinum. J Comp Physiol 125:217–225
Patterson RD, Green DM (1978) Auditory masking. In: Carterette EC, Friedman MP (eds) Handbook of perception, vol IV. Academic Press, New York London, pp 337–361
Pickles JO (1975) Normal critical bands in the cat. Acta Otolaryngol 80:245–254
Pickles JO (1979) Psychophysical frequency resolution in the cat as determined by simultaneous masking and its relation to auditory nerve resolution. J Acoust Soc Am 66:1725–1732
Pickles JO, Comis SD (1976) Auditory-nerve-fiber bandwidths and critical bandwidths in the cat. J Acoust Soc Am 60:1151–1156
Rhode WS, Geisler CD, Kennedy DT (1978) Auditory nerve fiber responses to wide-band noise and tone combinations. J Neurophysiol 41:692–704
Sachs MB, Kiang NYS (1968) Two-tone inhibition in auditory nerve fibers. J Acoust Soc Am 43: 1120–1128
Saunders JC, Denny RM, Bock GR (1978) Critical bands in the parakeet (Melopsittacus undulatus). J Comp Physiol 125:359–365
Scharf B (1970) Critical bands. In: Tobias JV (ed) Foundations of modern auditory theory, vol 1. Academic Press, New York London, pp 159–202
Smith RL (1979) Adaptation, saturation, and physiological masking in single auditory-nerve fibers. J Acoust Soc Am 65:166–178
Watson CS (1963) Masking of tones by noise for the cat. J Acoust Soc Am 35:167–172
Zwicker E, Feldtkeller R (1967) Das Ohr als Nachrichtenempfänger. Hirzel, Stuttgart
Author information
Authors and Affiliations
Additional information
This study was conducted at Cornell University and supported by grants of the Deutsche Forschungsgemeinschaft to G. Ehret (Eh 53/4) and of the N.I.H. to R.R. Capranica (NS-09244). We gratefully acknowledge A.J.M. Moffat for technical help and valuable comments on the manuscript.
Rights and permissions
About this article
Cite this article
Ehret, G., Capranica, R.R. Masking patterns and filter characteristics of auditory nerve fibers in the green treefrog (Hyla cinerea). J. Comp. Physiol. 141, 1–12 (1980). https://doi.org/10.1007/BF00611872
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00611872