Summary
-
1.
Five species of neotropical bats, which emit echolocation pulses different than those employed by bats previously studied, were investigated in an attempt to find corresponding differences in mechanisms of neural analysis. Evoked potentials were recorded from the posterior colliculi and more peripheral levels in anesthetized specimens.
-
2.
Each species was found to be most sensitive in approximately the same frequency range it uses in its emitted pulses: Chilonycteris rubiginosa at 63 kc/s, Pteronotus suapurensis at 50 kc/s, Saccopteryx bilineata at 42 kc/s, Phyllostomus hastatus at 50 kc/s, and Carollia perspicillata at 80 kc/s. Sensitivity was especially sharply “tuned” in the bats employing predominantly constant frequency pulses (Chilonycteris and Saccopteryx).
-
3.
Chilonycteris, Saccopterys and Pteronotus have prominent evoked potential responses to the end of a tone pip. In Chilonycteris and Saccopteryx these “off”-responses are extremely sharply tuned to a 2–5 kc/s frequency band centered just below the frequency of greatest sensitivity of the “on” response. The presence of an “off”-response appears to be correlated with the use of long, predominantly constant frequency pulses.
-
4.
The rate of recovery of responsiveness following an initial signal varied, being rapid at the level of the colliculus in Phyllostomus and Carollia (100% in 2–3 msec, slight supranormal responsiveness, and no subsequent depression), also rapid in Pteronotus, (but with an unusual degree of facilitation of responsiveness at intervals of 1–2 msec, followed by 5–10 msec of deep depression), and comparatively slow in Chilonycteris and Saccopteryx (full recovery in 10 msec or more).
-
5.
In bats using long orientation pulses which overlap with returning echoes (Chilonycteris and Saccopteryx), the “off”-responses are found to provide a more visible record of the presence of echoes and their time of arrival than do the “on”-responses.
-
6.
Chilonycteris respond to the orientation pulses of other Chilonycteris with prominent “off”-responses, which apparently are evoked by the termination of the constant frequency portion of each pulse rather than the downward FM sweep.
-
7.
Phyllostomus and Chilonycteris are sharply sensitive to changes in signal angle, Pteronotus is moderately so, and Saccopteryx and Carollia are relatively insensitive to angle at the level of the colliculus. In Saccopteryx and Carrollia the auditory nerve response is more sharply sensitive to angular change of the signal.
-
8.
In several species, but most prominently in Pteronotus, large DC potentials, of the same duration as the signal, were recorded in the vicinity of the cochlea and VIII nerve. These potentials were probably “summating potentials” and sometimes showed reversal of polarity with changes in signal frequency.
-
9.
In one preparation (Pteronotus), a DC potential was seen that was apparently contralateral in origin, had a latency 1 msec longer than the ipsilateral “summating potential”, and showed adaptation suggestive of a neural origin. It is suggested that a direct neural pathway between the two ears may exist.
-
10.
It is concluded that species differences in response patterns are at least in part a result of evolutionary adaptation governed by the type of emitted orientation sounds employed.
Similar content being viewed by others
References
Fex, J.: Efferent inhibition in the cochlea related to hair-cell dc activity: study of postsynaptic activity of the crossed olivo-cochlear fibres in the cat. J. acoust. Soc. Amer. 41, 666–676 (1967).
Friend, J. H., Suga, N., Suthers, R. A.: Neural responses in the inferior colliculus of echolocating bats to artifical orientation sounds and echoes. J. cell. Physiol. 67, 319–332 (1966).
Griffin, D. R.: Listening in the dark. New Haven: Yale Univ. Press 1958.
—: Comparative studies of the orientation sounds of bats. Symp. zool. Soc. (Lond.) 7, 61–72 (1962).
—, Novick, A.: Acoustic orientation of neotropical bats. J. exp. Zool. 130, 251–300 (1955).
Grinnell, A. D.: Neurophysiological correlates of echolocation in bats. Ph. D. thesis, Harvard Univ., 1962. Tech. Report No 30, Office of Naval Research. Contr. No 1866 (12) NR-301-219 (1962).
—: The neurophysiology of audition in bats: Intensity and frequency parameters. J. Physiol. (Lond.) 167, 38–66 (1963a).
—: The neurophysiology of audition in bats: Temporal parameters. J. Physiol. (Lond.) 167, 67–96 (1963b).
—: The neurophysiology of audition in bats: Directional localization and binaural interaction. J. Physiol. (Lond.) 167, 97–113 (1963c).
—: The neurophysiology of audition in bats: Resistance to interference. J. Physiol. (Lond.) 167, 114–127 (1963d).
—: Mechanisms of overcoming interference in echolocating animals. In: Animal sonar systems, ed. R-G. Busnel, p. 451–481. Jouy-en-Josas-78, France: Imprimerie Louis-Jean (gab) 1967.
—: The comparative physiology of hearing. Ann. Rev. Physiol. 31, 545–580 (1969).
—, Griffin, D. R.: The sensitivity of echolocation in bats. Biol. Bull. 114, 10–22 (1958).
—, Grinnell, V. S.: Neural correlates of vertical localization by echo-locating bats. J. Physiol. (Lond.) 181, 830–851 (1965).
Grummon, R. A., Novick, A.: Obstacle avoidance in the bat Macrotus mexicanus. Physiol. Zool. 36, 361–369 (1963).
Harrison, J. B.: Temperature effects on response in the auditory system of the little brown bat, Myotis lucifugus. Physiol. Zool. 38, 34–48 (1965).
Henson, O. W., Jr.: The activity and function of the middle ear muscles in echolocating bats. J. Physiol. (Lond.) 180, 871–887 (1965).
—: The perception and analysis of biosonar signals by bats. In: Animal sonar systems, ed. R.-G. Busnel. Jouy-en-Josas-78, France: Laboratoire de Physiologie Acoustique 1967.
Hubel, D. H.: Tungsten microelectrode for recording from single units. Science 125, 549–550 (1967).
Kuhl, W. G., Schodder, R., Schröder, F.-K.: Condenser transmitters with solid dielectrics for airborn ultrasonics. Acustica 4, 519–532 (1954).
McCue, J. J. G.: Ultrasonic instrumentation for research on bats. IRE Internat. Convention Record, 310–315 (1961).
Novick, A.: Orientation in neotropical bats. I. Natalidae and emballonuridae. J. Mammalogy 43, 449–455 (1962).
—: Pulse duration in the echolocation of insects by the bat, Pteronotus. Ergebn. Biol. 26, 21–26 (1963).
—, Vaisnys, J. R.: Echolocation of flying insects by the bat, Chilonycteris parnellii. Biol. Bull. 127, 478–488 (1964).
Pye, A.: The structure of the cochlea in Chiroptera. I. Microchiroptera: Emballonuroidea and Rhinolophoidea. J. Morph. 118, 495–510 (1966a).
—: The structure of the cochlea in Chiroptera. III. Microchiroptera: Phyllostomato idea. J. Morph. 121, 241–254 (1967).
Sandel, T. T., Kiang, N. Y.-S.: Off-responses from the auditory cortex of anesthetized cats: effects of stimulus parameters. Arch. ital. Biol. 99, 105–120 (1961).
Schnitzler, H.-U.: Discrimination of thin wires by flying horseshoe bats (Rhino lophidae). In: Animal sonar systems, ed. R.-G. Busnel, p. 69–87. Jouy-en Josas-78, France: Imprimerie Louis-Jean (gab) 1967.
—: Die Ultraschall-Ortungslaute der Hufeisen-Fledermäuse (Chiroptera-Rhinolophi dae) in verschiedenen Orientierungssituationen. Z. vergl. Physiol. 57, 376–408 (1968).
Suga, N.: Recovery cycles and responses to frequency modulated tone pulses in auditory neurons of echolocating bats. J. Physiol. (Lond.) 175, 50–80 (1964a).
—: Single unit activity in cochlear nucleus and inferior colliculus of echo-locating bats. J. Physiol. (Lond.) 172, 449–474 (1964b).
—: Analysis of frequency modulated sound by auditory neurons of echolocating bats. J. Physiol. (Lond.) 179, 26–53 (1965a).
—: Functional properties of auditory neurons in the cortex of echolocating bats. J. Physiol. (Lond.) 181, 671–700 (1965b).
—: Analysis of frequency-modulated and complex sounds by single auditory neurones of bats. J. Physiol. (Lond.) 198, 51–80 (1968).
Vasiliev, A. G.: A comparative description of the auditory system of bats Vespertilionidae and Rhinolophidae (Electrophysiological data). Dokl. Akad Nauk SSSR 175, 1414–1417 (1967).
Author information
Authors and Affiliations
Additional information
It is a pleasure to acknowledge the generosity of the Smithsonian Institution-Canal Zone Biological Area in making their facilities available for this research. Support was provided by a grant from NIH to the author, and by grants fron NSF, NIH, AFOSR and ONR to Prof. T. H. Bullock.
Rights and permissions
About this article
Cite this article
Grinnell, A.D. Comparative auditory neurophysiology of neotropical bats employing different echolocation signals. Z. Vergl. Physiol. 68, 117–153 (1970). https://doi.org/10.1007/BF00297691
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00297691