Summary
-
1.
Recordings were made from 135 single inferior colliculus neurons of the Greater horseshoe bat,Rhinolophus ferrumequinum. These bats emit sonar signals which are characterized by a long constant frequency (CF-) component and a terminal frequency modulated (FM-) component. The responses of the units to CF- and FM-stimuli with different modulation heights, durations and directions were studied.
-
2.
The majority of single units studied had minimum thresholds that were either equal for CF- and FM-signals of the same duration or lower for the CF-stimulus. Only rarely was the sensitivity for FM-signals higher than for a CF-signal.
-
3.
With FM-signals the response properties of units with best frequencies between 65–81 kHz, i.e. in the frequency range of the FM-component of the echolocation call, did not differ significantly from units with best frequencies in lower frequency ranges. Relatively many units with best frequencies in the filter region of the audiogram (81–88 kHz) required FM-signals with particular modulation heights and rates to elicit excitatory responses.
-
4.
Response patterns and spike count functions were found to differ with CF- vs. FM-signals. The most common difference was a smaller number of impulses per stimulus and a temporally more restricted (‘phasic’) discharge pattern to FM-signals than to CF-signals. Greater discharge activity to FM-signals occurred in only a few units. ‘Latency constant’ and ‘FM-specialized’ neurons, as reported for other species were also found.
-
5.
Inhibition was frequently observed with FM-stimuli in spontaneously active neurons. An accurate prediction of a neuron's response to FM-signals from knowledge of the excitatory and inhibitory response areas to CF-signals was not always possible.
-
6.
The responses of ‘FM-specialized’ neurons to the FM-component of a CF-FM-stimulus was not significantly altered by the presence of a CF-component in the filter region of the audiogram.
-
7.
Responses of single units to signal and noise combinations are described.
-
8.
Data are discussed in relation to results on the processing of FM-signals in other bats.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Abbreviations
- BF :
-
best frequency
- CF :
-
constant frequency
- FM :
-
frequency modulated
- FTC :
-
frequency-threshold-curve
- IC :
-
inferior colliculus
- SNR :
-
signal/noise ratio
- SPL :
-
sound pressure level re. 0.00002 N·m−2
References
Grinnell, A.D.: Comparative auditory physiology of neotropical bats employing different echolocation signals. Z. Vergl. Physiol.68, 117–153 (1970)
Grinnell, A.D.: Neural processing mechanisms in echolocating bats correlated with differences in emitted sounds. J. Acoust. Soc. Am.54, 147–156 (1973)
Long, G.R., Schnitzler, H.-U.: Behavioural audiograms from the bat,Rhinolophus ferrumequinum. J. Comp. Physiol.100, 211–219 (1975)
Machmerth, H., Theiss, D., Schnitzler, H.-U.: Konstruktion eines Luftultraschallgebers mit konstantem Frequenzgang im Bereich von 15 kHz–130 kHz. Acustica34, 81–85 (1975)
Möller, J.: Die Funktion von Hemmeinflüssen bei Neuronen der lemniscalen Hörbahn bei der Echoortung vonRhinolophus ferrumequinum. Doctoral dissertation, University of Stuttgart (1977)
Möller, J., Neuweiler, G., Zöller, H.: Response characteristics of inferior colliculus neurons of the awake CF-FM batRhinolophus ferrumequinum. I. Single tone stimulation. J. Comp. Physiol.125, 217–225 (1978)
Neuweiler, G.: Neurophysiologische Untersuchungen am Echoortungssystem der großen Hufeisennase,Rhinolophus ferrumequinum Schreber, 1774. Z. Vergl. Physiol.67, 273–306 (1970)
Neuweiler, G.: Recognition mechanisms in echolocation of bats. In: Recognition of complex acoustic signals. Bullock, T.H. (ed.), pp. 111–126. Berlin: Dahlem Konferenzen 1977
Neuweiler, G., Vater, M.: Response patterns to pure tone of cochlear nucleus units in the CF-FM bat,Rhinolophus ferrumequinum. J. Comp. Physiol.115, 119–133 (1977)
Novick, A.: Echolocation in bats: Some aspects of pulse design. Am. Sci.59, 198–209 (1971)
Pollak, G.D., Marsh, D.S., Bodenhamer, R., Souther, A.: Characteristics of phasic-on neurons in inferior colliculus of unanaesthetized bats with observations relating to mechanisms for echoranging. J. Neurophysiol.40, 926–942 (1977a)
Pollak, G.D., Bodenhamer, R., Marsh, D.S., Souther, A.: Recovery cycles of single neurons in the inferior colliculus of unanaesthetized bats obtained with frequency-modulated and constantfrequency sounds. J. Comp. Physiol.120, 215–250 (1977b)
Pollak, G.D., Marsh, D.S., Bodenhamer, R., Souther, A.: A single unit analysis of the inferior colliculus in unanaesthetized bats: Response patterns and spike count functions generated by constant-frequency and frequency-modulated sounds. J. Neurophysiol.41, 677–692 (1978)
Rose, J.E., Greenwood, D.D., Goldberg, J.M., Hind, J.E.: Some discharge characteristics of single neurons in the inferior colliculus of the cat. Tonotopic organization, relation of spike counts to tone intensity, and firing patterns of single elements. J. Neurophysiol.26, 294–320 (1963)
Schnitzler, H.-U.: Die Ultraschall-Ortungslaute der Hufeisenfledermäuse (Chiroptera-Rhinolophidae) in verschiedenen Ortungssituationen. Z. Vergl. Physiol.57, 376–408 (1968)
Schuller, G.: Echoortung beiRhinolophus ferrumequinum mit frequenzmodulierten Lauten. Evoked potentials im Colliculus inferior. J. Comp. Physiol.77, 306–331 (1972)
Schuller, G., Pollak, G.: Disproportionate frequency representation in the inferior colliculus of Doppler-compensating Greater Horseshoe bats: Evidence for an acoustic fovea. J. Comp. Physiol.132, 47–54 (1979)
Schuller, G., Neuweiler, G., Schnitzler, H.-U.: Collicular responses to the frequency-modulated final part of echolocation sounds inRhinolophus ferrumequinum. Z. Vergl. Physiol.74, 153–155 (1971)
Schuller, G., Beuter, K., Schnitzler, H.-U.: Response to frequency shifted artificial echoes in the batRhinolophus ferrumequinum. J. Comp. Physiol.89, 275–286 (1974)
Simmons, J.A.: The resolution of target range by echolocating bats. J. Acoust. Soc. Am.54, 157–173 (1973)
Simmons, J.A., Howell, D.J., Suga, N.: Information content of bat sonar echoes. Am. Sci.63, 204–215 (1975)
Simmons, J.A., Lavender, W.A., Lavender, B.A., Childs, J.E., Hulebak, K., Rigden, M.R., Sherman, J., Woolman, B.: Echolocation in freetailed bats (Tadarida). J. Comp. Physiol.125, 291–299 (1978)
Suga, N.: Echoranging neurons in inferior colliculus of bats. Science170, 449–452 (1970)
Suga, N.: Feature extraction in the auditory system of bats. In: Basic mechanisms in hearing. Møller, A.R. (ed.). New York, London: Academic Press 1973
Suga, N.: Specializations of the auditory system for reception and processing of species-specific sounds. Fed. Proc.37, 2342–2354 (1978)
Suga, N., Simmons, J.A., Jen, P. H.-S.: Peripheral specializations for fine frequency analysis of Doppler-shifted echoes in the auditory system of the “CF-FM” bat,Pteronotus parnellii. J. Exp. Biol.63, 161–192 (1975)
Suga, N., Neuweiler, G., Möller, J.: Peripheral auditory tuning for fine frequency analysis in the CF-FM bat,Rhinolophus ferrumequinum. IV. Properties of peripheral auditory neurons. J. Comp. Physiol.106, 111–125 (1976)
Vater, M., Schlegel, P., Zöller, H.: Comparative auditory neurophysiology of the inferior colliculus of two Molossid bats,Molossus ater andMolossus molossus. I. Gross evoked potentials and single unit responses to pure tones. J. Comp. Physiol.131, 137–145 (1979)
Vater, M., Schlegel, P.: Comparative auditory neurophysiology of the inferior colliculus of two Molossid bats,Molossus ater andMolossus molossus. II. Single unit responses to frequencymodulated signals and signal and noise combinations. J. Comp. Physiol.131, 147–160 (1979)
Whitfield, I.C., Evans, E.F.: Responses of auditory cortical neurons to stimuli of changing frequency. J. Neurophysiol.28, 655–672 (1965)
Author information
Authors and Affiliations
Additional information
I thank the members of the Arbeitskreis Neuro- und Rezeptorphysiologie for their interest and discussions, Dr. O.W. Henson for correction of the English version and Heike Hahn for valuable technical assistance.
Supported by the grants: Deutsche Forschungsgemeinschaft Br 593/2, Ne 146/8, Ne 146/10; SFB 45
Rights and permissions
About this article
Cite this article
Vater, M. Single unit responses to linear frequency-modulations in the inferior colliculus of the Greater horseshoe bat,Rhinolophus ferumequinum . J. Comp. Physiol. 141, 249–264 (1981). https://doi.org/10.1007/BF01342671
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01342671