TY - JOUR A1 - Korniienko, Yevheniia A1 - Nguyen, Linh A1 - Baumgartner, Stephanie A1 - Vater, Marianne A1 - Tiedemann, Ralph A1 - Kirschbaum, Frank T1 - Correction to: Intragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua male x C. compressirostris female) are fertile (vol 206, pg 571, 2020) JF - Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology Y1 - 2021 U6 - https://doi.org/10.1007/s00359-021-01513-2 SN - 0340-7594 SN - 1432-1351 VL - 207 IS - 6 SP - 773 EP - 773 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Nguyen, Manh Duy Linh A1 - Mamonekene, Victor A1 - Vater, Marianne A1 - Bartsch, Peter A1 - Tiedemann, Ralph A1 - Kirschbaum, Frank T1 - Ontogeny of electric organ and electric organ discharge in Campylomormyrus rhynchophorus (Teleostei: Mormyridae) JF - Journal of comparative physiology; A, Neuroethology, sensory, neural, and behavioral physiology N2 - The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte. KW - Weakly electric fish KW - Development KW - Electric organ discharge KW - Electric KW - organ KW - Electrocyte features Y1 - 2020 U6 - https://doi.org/10.1007/s00359-020-01411-z SN - 0340-7594 SN - 1432-1351 VL - 206 IS - 3 SP - 453 EP - 466 PB - Springer CY - Berlin ; Heidelberg ER - TY - JOUR A1 - Korniienko, Yevheniia A1 - Nguyen, Linh A1 - Baumgartner, Stephanie A1 - Vater, Marianne A1 - Tiedemann, Ralph A1 - Kirschbaum, Frank T1 - Intragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua male x C. compressirostris female) are fertile JF - Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology N2 - Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids betweenCampylomormyrus tamandua male x C. compressirostris female were investigated concerning: (1) fertility; (2) survival of F2-fish and (3) new gene combinations in the F2-generation concerning the structure of the electric organ and features of the electric organ discharge. These F1-hybrids achieved sexual maturity at about 12-13.5 cm total length. A breeding group comprising six males and 13 females spawned 28 times naturally proving these F1-fish to be fertile. On average 228 eggs were spawned, the average fertilization rate was 47.8%. Eggs started to hatch 70-72 h after fertilization, average hatching rate was 95.6%. Average mortality rate during embryonic development amounted to 2.3%. Average malformation rate during the free embryonic stage was 27.7%. Exogenous feeding started on day 11. In total, we raised 353 normally developed larvae all of which died consecutively, the oldest specimen reaching an age of 5 months. During survival, the activities of the larval and adult electric organs were recorded and the structure of the adult electric organ was investigated histologically. KW - mormyridae KW - campylomormyrus KW - F1-hybrids KW - F2-hybrids KW - fertility Y1 - 2020 U6 - https://doi.org/10.1007/s00359-020-01425-7 SN - 0340-7594 SN - 1432-1351 VL - 206 IS - 4 SP - 571 EP - 585 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Korniienko, Yevheniia A1 - Tiedemann, Ralph A1 - Vater, Marianne A1 - Kirschbaum, Frank T1 - Ontogeny of the electric organ discharge and of the papillae of the electrocytes in the weakly electric fish Campylomormyrus rhynchophorus (Teleostei: Mormyridae) JF - The journal of comparative neurology N2 - The electric organ of the mormyrid weakly electric fish,Campylomormyrus rhynchophorus(Boulenger, 1898), undergoes changes in both the electric organ discharge (EOD) and the light and electron microscopic morphology as the fish mature from the juvenile to the adult form. Of particular interest was the appearance of papillae, surface specializations of the uninnervated anterior face of the electrocyte, which have been hypothesized to increase the duration of the EOD. In a 24.5 mm long juvenile the adult electric organ (EO) was not yet functional, and the electrocytes lacked papillae. A 40 mm long juvenile, which produced a short biphasic EOD of 1.3 ms duration, shows small papillae (average area 136 mu m(2)). In contrast, the EOD of a 79 mm long juvenile was triphasic. The large increase in duration of the EOD to 23.2 ms was accompanied by a small change in size of the papillae (average area 159 mu m(2)). Similarly, a 150 mm long adult produced a triphasic EOD of comparable duration to the younger stage (24.7 ms) but featured a prominent increase in size of the papillae (average area 402 mu m(2)). Thus, there was no linear correlation between EOD duration and papillary size. The most prominent ultrastructural change was at the level of the myofilaments, which regularly extended into the papillae, only in the oldest specimen-probably serving a supporting function. Physiological mechanisms, like gene expression levels, as demonstrated in someCampylomormyrusspecies, might be more important concerning the duration of the EOD. KW - Campylomormyrus KW - electric organ discharge KW - electrocyte ontogeny KW - electrocyte ultrastructure KW - papillae Y1 - 2020 U6 - https://doi.org/10.1002/cne.25003 SN - 0021-9967 SN - 1096-9861 VL - 529 IS - 5 SP - 1052 EP - 1065 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kössl, Manfred A1 - Hechavarria, Julio A1 - Voss, Cornelia A1 - Schaefer, Markus A1 - Vater, Marianne T1 - Bat auditory cortex - model for general mammalian auditory computation or special design solution for active time perception? JF - European journal of neuroscience N2 - Audition in bats serves passive orientation, alerting functions and communication as it does in other vertebrates. In addition, bats have evolved echolocation for orientation and prey detection and capture. This put a selective pressure on the auditory system in regard to echolocation-relevant temporal computation and frequency analysis. The present review attempts to evaluate in which respect the processing modules of bat auditory cortex (AC) are a model for typical mammalian AC function or are designed for echolocation-unique purposes. We conclude that, while cortical area arrangement and cortical frequency processing does not deviate greatly from that of other mammals, the echo delay time-sensitive dorsal cortex regions contain special designs for very powerful time perception. Different bat species have either a unique chronotopic cortex topography or a distributed salt-and-pepper representation of echo delay. The two designs seem to enable similar behavioural performance. KW - chronotopy KW - echolocation KW - fovea KW - salt-and-pepper KW - target range Y1 - 2015 U6 - https://doi.org/10.1111/ejn.12801 SN - 0953-816X SN - 1460-9568 VL - 41 IS - 5 SP - 518 EP - 532 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Paul, Christiane A1 - Mamonekene, Victor A1 - Vater, Marianne A1 - Feulner, Philine G. D. A1 - Engelmann, Jacob A1 - Tiedemann, Ralph A1 - Kirschbaum, Frank T1 - Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae) JF - Journal of comparative physiology : A, Neuroethology, sensory, neural, and behavioral physiology N2 - The electric organ (EO) of weakly electric mormyrids consists of flat, disk-shaped electrocytes with distinct anterior and posterior faces. There are multiple species-characteristic patterns in the geometry of the electrocytes and their innervation. To further correlate electric organ discharge (EOD) with EO anatomy, we examined four species of the mormyrid genus Campylomormyrus possessing clearly distinct EODs. In C. compressirostris, C. numenius, and C. tshokwe, all of which display biphasic EODs, the posterior face of the electrocytes forms evaginations merging to a stalk system receiving the innervation. In C. tamandua that emits a triphasic EOD, the small stalks of the electrocyte penetrate the electrocyte anteriorly before merging on the anterior side to receive the innervation. Additional differences in electrocyte anatomy among the former three species with the same EO geometry could be associated with further characteristics of their EODs. Furthermore, in C. numenius, ontogenetic changes in EO anatomy correlate with profound changes in the EOD. In the juvenile the anterior face of the electrocyte is smooth, whereas in the adult it exhibits pronounced surface foldings. This anatomical difference, together with disparities in the degree of stalk furcation, probably contributes to the about 12 times longer EOD in the adult. KW - Mormyridae KW - Campylomormyrus KW - Electric organ discharge KW - Electrocyte geometry KW - Electric organ ontogeny Y1 - 2015 U6 - https://doi.org/10.1007/s00359-015-0995-6 SN - 0340-7594 SN - 1432-1351 VL - 201 IS - 4 SP - 357 EP - 374 PB - Springer CY - New York ER - TY - JOUR A1 - Koessl, M. A1 - Hechavarria, J. C. A1 - Voss, C. A1 - Macias, S. A1 - Mora, E. C. A1 - Vater, Marianne T1 - Neural maps for target range in the auditory cortex of echolocating bats JF - Current opinion in neurobiology : reviews of all advances ; evaluation of key references ; comprehensive listing of papers N2 - Computational brain maps as opposed to maps of receptor surfaces strongly reflect functional neuronal design principles. In echolocating bats, computational maps are established that topographically represent the distance of objects. These target range maps are derived from the temporal delay between emitted call and returning echo and constitute a regular representation of time (chronotopy). Basic features of these maps are innate, and in different bat species the map size and precision varies. An inherent advantage of target range maps is the implementation of mechanisms for lateral inhibition and excitatory feedback. Both can help to focus target ranging depending on the actual echolocation situation. However, these maps are not absolutely necessary for bat echolocation since there are bat species without cortical target-distance maps, which use alternative ensemble computation mechanisms. Y1 - 2014 U6 - https://doi.org/10.1016/j.conb.2013.08.016 SN - 0959-4388 SN - 1873-6882 VL - 24 SP - 68 EP - 75 PB - Elsevier CY - London ER - TY - JOUR A1 - Vater, Marianne A1 - Koessl, Manfred T1 - Comparative aspects of cochlear functional organization in mammals JF - Hearing research N2 - This review addresses the functional organization of the mammalian cochlea under a comparative and evolutionary perspective. A comparison of the monotreme cochlea with that of marsupial and placental mammals highlights important evolutionary steps towards a hearing organ dedicated to process higher frequencies and a larger frequency range than found in non-mammalian vertebrates. Among placental mammals, there are numerous cochlear specializations which relate to hearing range in adaptation to specific habitats that are superimposed on a common basic design. These are illustrated by examples of specialist ears which evolved excellent high frequency hearing and echolocation (bats and dolphins) and by the example of subterranean rodents with ears devoted to processing low frequencies. Furthermore, structural functional correlations important for tonotopic cochlear organization and predictions of hearing capabilities are discussed. Y1 - 2011 U6 - https://doi.org/10.1016/j.heares.2010.05.018 SN - 0378-5955 VL - 273 IS - 1-2 SP - 89 EP - 99 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hagemann, Cornelia A1 - Vater, Marianne A1 - Koessl, Manfred T1 - Comparison of properties of cortical echo delay-tuning in the short-tailed fruit bat and the mustached bat JF - Journal of comparative physiology : A, Neuroethology, sensory, neural, and behavioral physiology N2 - Target-distance computation by cortical neurons sensitive to echo delay is an essential characteristic of the auditory system of insectivorous bats. To assess if functional requirements such as detection of small insects versus larger stationary surfaces of plants are reflected in cortical properties, we compare delay-tuned neurons in a frugivorous (C. perspicillata, CP) and an insectivorous (P. parnellii, PP) bat species that belong to related families within the superfamily of Noctilionoidea. The bandwidth and shape of delay-tuning curves and the range of characteristic delays are similar in both species and hence are not related to different echolocation strategies. Most units respond at 2-6 ms echo delay with most sensitive thresholds of 20-30 dB SPL. In CP, units tuned to delays > 12 ms are slightly more abundant and are more sensitive than in PP. All delay-tuned neurons in CP reliably respond to single pure-tone stimuli, whereas such responses are only observed in 49% of delay-tuned units in PP. The cortical representation of echo delay (chronotopy) covers a larger area in CP but is less precise than described in PP. Since chronotopy is absent in certain other insectivorous bat species, it is open if these differences in topography are related to echolocation behaviour. KW - Echolocation KW - Auditory cortex KW - Chronotopy KW - Carollia perspicillata KW - Pteronotus parnellii Y1 - 2011 U6 - https://doi.org/10.1007/s00359-010-0530-8 SN - 0340-7594 VL - 197 IS - 5 SP - 605 EP - 613 PB - Springer CY - New York ER - TY - JOUR A1 - Kössl, Manfred A1 - Voss, Cornelia A1 - Mora, Emanuel C. A1 - Macias, Silvio A1 - Föller, Elisabeth A1 - Vater, Marianne T1 - Auditory cortex of newborn bats is prewired for echolocation JF - Nature Communications N2 - Neuronal computation of object distance from echo delay is an essential task that echolocating bats must master for spatial orientation and the capture of prey. In the dorsal auditory cortex of bats, neurons specifically respond to combinations of short frequency-modulated components of emitted call and delayed echo. These delay-tuned neurons are thought to serve in target range calculation. It is unknown whether neuronal correlates of active space perception are established by experience-dependent plasticity or by innate mechanisms. Here we demonstrate that in the first postnatal week, before onset of echolocation and flight, dorsal auditory cortex already contains functional circuits that calculate distance from the temporal separation of a simulated pulse and echo. This innate cortical implementation of a purely computational processing mechanism for sonar ranging should enhance survival of juvenile bats when they first engage in active echolocation behaviour and flight. Y1 - 2012 U6 - https://doi.org/10.1038/ncomms1782 SN - 2041-1723 VL - 3 IS - 2 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Hechavarria, Julio C. A1 - Macias, Silvio A1 - Vater, Marianne A1 - Mora, Emanuel C. A1 - Kössl, Manfred T1 - Evolution of neuronal mechanisms for echolocation specializations for target-range computation in bats of the genus Pteronotus JF - The journal of the Acoustical Society of America N2 - Delay tuning was studied in the auditory cortex of Pteronotus quadridens. All the 136 delay-tuned units that were studied responded strongly to heteroharmonic pulse-echo pairs presented at specific delays. In the heteroharmonic pairs, the first sonar call harmonic marks the timing of pulse emission while one of the higher harmonics (second or third) indicates the timing of the echo. Delay-tuned units are organized chronotopically along a rostrocaudal axis according to their characteristic delay. There is no obvious indication of multiple cortical axes specialized in the processing of different harmonic combinations of pulse and echo. Results of this study serve for a straight comparison of cortical delay-tuning between P. quadridens and the well-studied mustached bat, Pteronotus parnellii. These two species stem from the most recent and most basal nodes in the Pteronotus lineage, respectively. P. quadridens and P. parnellii use comparable heteroharmonic target-range computation strategies even though they do not use biosonar calls of a similar design. P. quadridens uses short constant-frequency (CF)/frequency-modulated (FM) echolocation calls, while P. parnellii uses long CF/FM calls. The ability to perform "heteroharmonic" target-range computations might be an ancestral neuronal specialization of the genus Pteronotus that was subjected to positive Darwinian selection in the evolution. Y1 - 2013 U6 - https://doi.org/10.1121/1.4768794 SN - 0001-4966 VL - 133 IS - 1 SP - 570 EP - 578 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Hechavarria, Julio C. A1 - Macias, Silvio A1 - Vater, Marianne A1 - Voss, Cornelia A1 - Mora, Emanuel C. A1 - Kossl, Manfred T1 - Blurry topography for precise target-distance computations in the auditory cortex of echolocating bats JF - Nature Communications N2 - Echolocating bats use the time from biosonar pulse emission to the arrival of echo (defined as echo delay) to calculate the space depth of targets. In the dorsal auditory cortex of several species, neurons that encode increasing echo delays are organized rostrocaudally in a topographic arrangement defined as chronotopy. Precise chronotopy could be important for precise target-distance computations. Here we show that in the cortex of three echolocating bat species (Pteronotus quadridens, Pteronotus parnellii and Carollia perspicillata), chronotopy is not precise but blurry. In all three species, neurons throughout the chronotopic map are driven by short echo delays that indicate the presence of close targets and the robustness of map organization depends on the parameter of the receptive field used to characterize neuronal tuning. The timing of cortical responses (latency and duration) provides a binding code that could be important for assembling acoustic scenes using echo delay information from objects with different space depths. Y1 - 2013 U6 - https://doi.org/10.1038/ncomms3587 SN - 2041-1723 VL - 4 IS - 10 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Huggenberger, Stefan A1 - Vater, Marianne A1 - Deisz, Rudolf A. T1 - Interlaminar differences of intrinsic properties of pyramidal neurons in the auditory cortex of mice N2 - Cortical information processing depends crucially upon intrinsic neuronal properties modulating a given synaptic input, in addition to integration of excitatory and inhibitory inputs. These intrinsic mechanisms are poorly understood in sensory cortex areas. We therefore investigated neuronal properties in slices of the auditory cortex (AC) of normal hearing mice using whole-cell patch-clamp recordings of pyramidal neurons in layers II/III, IV, V, and VI in the current- and voltage clamp mode. A total of 234 pyramidal neurons were included in the analysis revealing distinct laminar differences. Regular spiking (RS) neurons in layer II/III have significantly lower resting membrane potential, higher threshold for action potential generation, and larger K-ir and I-h amplitudes compared with layer V and VI RS neurons. These currents could improve temporal resolution in the upper layers of the AC. Additionally, the presence of a T-type Ca2+ current could be an important factor of RS neurons in these upper layers to amplify temporally closely correlated inputs. Compared with upper layers, lower layers (V and VI) exhibit a higher relative abundance of intrinsic bursting neurons. These neurons may provide layer-specific transfer functions for interlaminar, intercortical, and corticofugal information processing. Y1 - 2009 UR - http://cercor.oxfordjournals.org/ U6 - https://doi.org/10.1093/cercor/bhn143 SN - 1047-3211 ER - TY - JOUR A1 - Vater, Marianne A1 - Foeller, Elisabeth A1 - Mora, Emanuel C. A1 - Coro, Frank A1 - Russell, Ian J. A1 - Kössl, Manfred T1 - Postnatal maturation of primary auditory cortex in the mustached bat, pteronotus parnellii N2 - The primary auditory cortex (AI) of adult Pteronotus parnellii features a foveal representation of the second harmonic constant frequency (CF2) echolocation call component. In the corresponding Doppler-shifted constant frequency (DSCF) area, the 61 kHz range is over-represented for extraction of frequency-shift information in CF2 echoes. To assess to which degree AI postnatal maturation depends on active echolocation or/and reflects ongoing cochlear maturation, cortical neurons were recorded in juveniles up to postnatal day P29, before the bats are capable of active foraging.At P1-2, neurons in posterior AI are tuned sensitively to low frequencies (22-45 dB SPL, 28-35 kHz). Within the prospective DSCF area, neurons had insensitive responses (>60 dB SPL) to frequencies <40 kHz and lacked sensitive tuning curve tips. Up to P10, when bats do not yet actively echolocate, tonotopy is further developed and DSCF neurons respond to frequencies of 51-57 kHz with maximum tuning sharpness (Q(10dB)) of 57. Between P11 and 20, the frequency representation in AI includes higher frequencies anterior and dorsal to the DSCF area. More multipeaked neurons (33%) are found than at older age. In the oldest group, DSCF neurons are tuned to frequencies close to 61 kHz with Q(10dB) values <= 212, and threshold sensitivity, tuning sharpness and cortical latencies are adult-like. The data show that basic aspects of cortical tonotopy are established before the bats actively echolocate. Maturation of tonotopy, increase of tuning sharpness, and upward shift in the characteristic frequency of DSCF neurons appear to strongly reflect cochlear maturation. Y1 - 2010 UR - http://jn.physiology.org/ U6 - https://doi.org/10.1152/jn.00517.2009 SN - 0022-3077 ER - TY - JOUR A1 - Vater, Marianne T1 - Evolutionary plasticity of cochlear design in echolocating bats Y1 - 1997 SN - 981-02-2712-4 ER - TY - JOUR A1 - Vater, Marianne A1 - Covey, Ellen A1 - Casseday, John H. T1 - The columnar region of the ventral nucleus of the lateral lemniscus in the big brown bat (Eptesicus fuscus) : synaptic arrangements and structural correlates of feedforward inhibitory function Y1 - 1997 ER - TY - JOUR A1 - Kuhn, Birgit A1 - Vater, Marianne T1 - The postnatal development of F-actin in tension fibroblasts of the spiral ligament of the gerbil cochlea. Y1 - 1997 SN - 0378-5955 ER - TY - JOUR A1 - Kemmer, Michaela A1 - Vater, Marianne T1 - The distribution of GABA and glycine immunostaining in the cochlear nucleus of the mustached bat (Pteronotus parnellii). Y1 - 1997 ER - TY - JOUR A1 - Vater, Marianne T1 - Adaptation of the auditory periphery of bats for echolocation Y1 - 1998 SN - 1-56098-825-8 ER - TY - JOUR A1 - Kössl, Manfred A1 - Mora, Emanuel C. A1 - Coro, Frank A1 - Vater, Marianne T1 - Two-toned echolocation calls from Molossus molossus in Cuba. Y1 - 1999 SN - 0022-2372 ER - TY - JOUR A1 - Vater, Marianne T1 - Cochlear specializations in bats Y1 - 2000 SN - 3-527-27587-8 ER - TY - JOUR A1 - Vater, Marianne T1 - Cochlear specializations in bats Y1 - 2000 SN - 3-527-27587-8 ER - TY - JOUR A1 - Vater, Marianne T1 - Auditory brainstem processing in bats Y1 - 2000 SN - 3-527-27587- 8 ER - TY - JOUR A1 - Kössl, Manfred A1 - Vater, Marianne T1 - Consequences of outer hair cell damage for otoacoustic emissions and audiovocal feedback in the mustached bat Y1 - 2000 SN - 1525-3961 ER - TY - JOUR A1 - Vater, Marianne T1 - Evolutionary plasticity and ontogeny of the bat cochlea. Y1 - 2000 SN - 0-521-62632-3 ER - TY - JOUR A1 - Kemmer, Michaela A1 - Vater, Marianne T1 - Cellular and subcellular distribution of AMPA-type glutamate receptor subunits and metabotropic glutamate receptor 1alpha in the cochlear nucleus of the horseshoe bat (Rhinolophus rouxi). Y1 - 2001 SN - 0378-5955 ER - TY - JOUR A1 - Kemmer, Michaela A1 - Vater, Marianne T1 - Functional organization of the dorsal cochlear nucleus of the horseshoe bat (Rhinolophus rouxi) studied by GABA and glycine immunocytochemistry and electron microscopy. Y1 - 2001 SN - 0340-2061 ER - TY - JOUR A1 - Foeller, Elisabeth A1 - Vater, Marianne A1 - Kössl, Manfred T1 - Laminar analysis of inhibition in the gerbil primary auditory cortex. Y1 - 2001 SN - 1525-3961 ER - TY - JOUR A1 - LeGrimellec, Christian A1 - Giocondi, Marie-Cecile A1 - Lenoir, Marc A1 - Vater, Marianne A1 - Sposito, Gerard A1 - Pujol, Remy T1 - High-resolution three-dimensional imaging of the lateral plasma membrane of cochlear outer hair cells by atomic force microscopy Y1 - 2002 ER - TY - JOUR A1 - Mora, Emanuel C. A1 - Macias, S. A1 - Vater, Marianne A1 - Coro, Frank A1 - Kossl, Manfred T1 - Specializations for aerial hawking in the echolocation system of Molossus molossus (Molossidae, Chiroptera) N2 - While searching for prey, Molossus molossus broadcasts narrow-band calls of 11.42 ms organized in pairs of pulses that alternate in frequency. The first signal of the pair is at 34.5 kHz, the second at 39.6 kHz. Pairs of calls with changing frequencies were only emitted when the interpulse intervals were below 200 ms. Maximum duty cycles during search phase are close to 20%. Frequency alternation of search calls is interpreted as a mechanism for increasing duty cycle and thus the temporal continuity of scanning, as well as increasing the detection range. A neurophysiological correlate for the processing of search calls was found in the inferior colliculus. 64% of neurons respond to frequencies in the 30- to 40-kHz range and only in this frequency range were closed tuning curves found for levels below 40 dB SPL. In addition, 15% of the neurons have double-tuned frequency-threshold curves with best thresholds at 34 and 39 kHz. Differing from observations in other bats, approach calls of M. molossus are longer and of higher frequencies than search calls. Close to the roost, the call frequency is increased to 45.049.8 kHz and, in addition, extremely broadband signals are emitted. This demonstrates high plasticity of call design Y1 - 2004 SN - 0340-7594 ER -