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  • 1
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Many one-eared female crickets (Gryllus campestris andGryllus bimaculatus), whether the loss is due to surgery or to developmental accident, can maintain characteristic, stable courses with respect to the direction of male calling song, when tested on the Kramer spherical tread-mill. The error angles are usually less than 90°, so that Regen's (1924) remark about the success of such females in finding singing males is supported. 2. Some females with developmental unilateral hearing deficit, confirmed both histologically and by sparing of tracking after removal of the suspect leg, track nearly as accurately as normal animals with two ears. 3. Experiments in which tympana were immobilized with wax, whether tracking behavior or interneuron responses were monitored, show that the anterior tympanum — considered for some time to be irrelevant to hearing — mediates appreciable sound input to the auditory receptors, at least when the posterior tympana are blocked. 4. The above results resolve two current paradoxes regarding comparison of tympanum immobilization in behavior with the mechanics of receptor excitation: First, because even unambiguously one-eared animals can maintain stable sound-oriented courses, such tracking performance with waxed tympana does not argue that total tympanal immobilization spares some auditory function of that ear (cf. Schmitz et al. 1983). The argument assumes that tracking would not be expected if one ear were silenced; the assumption is evidently false. Second, it has been unclear why waxing of both posterior tympana raises tracking threshold only ca. 20 dB (Schmitz 1983) whereas the tympanalmechanics studies of Kleindienst et al. (1983) have suggested a much greater deficit. Our finding that one must wax the anterior tympana as well, in order to produce deficit greater than ca. 20 dB, clarifies the situation. That is, in the biophysical experiments both tympana of the leg were immobilized by the procedures used (pressure matching and water immersion), whereas in most current behavioral tympanum-waxing experiments (but not in those of Bailey and Thomson 1977) the anterior tympana have been ignored. 5. A novel behavioral effect was observed with all four tympana blocked. Thresholds for orientation were ca. 90–100 dB, but in every case the animals tended to walk away from the loudspeaker. 6. The search for an explanation of one-eared tracking leads us to analogies with the recovery from imbalance following such surgery as hemilabyrinthectomy in vertebrates. A ‘phantom tympanum’, on the side with deficit, could in principle participate in corrective tracking, by the usual notions of bilateral comparison.
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  • 3
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. In view of the surprising recent demonstration that developmentally one-eared female crickets can track sound sources (Huber et al. 1984), we have looked for correlates in the morphological and physiological properties of auditory interneurons of these animals. One foreleg was amputated in the 3rd/4th or penultimate (8/9th) larval instar; in both cases the leg regenerated without developing a functional ear. In the adult stage, these animals were studied first for their phonotactic behavior and then by intracellular recording and staining; three types of auditory interneurons in the prothoracic ganglion were identified: the omega neuron ON1, and the ascending neurons AN1 and AN2. 2. Of these three neuron types, those that normally receive excitatory input from the side now deafferented send dendrites across the midline of the ganglion, along specific pathways, to end in the auditory neuropil of the intact side (Figs. 1–4). 3. The new connections are functional, as shown by the responses of the neurons to synthesized calling songs presented to the remaining ear. With respect to the copying of chirp structure, threshold curves and intensity characteristics, these neurons respond like cells in intact animals that are presented with the same stimulus on the side ipsilateral to the main input region of the neurons (Figs. 2–4). The implication is that in animals with one ear missing, functional pathways within the central nervous system are reorganized, resulting in better orientation of one-eared animals.
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  • 4
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Physiological recordings were obtained from identified receptors in the tympanal organ ofGryllus bimaculatus. By immersing the prothoracic leg in Ringer solution and removing the anterior tympanic membrane the auditory receptors were exposed without significantly altering the frequency response of the auditory organ (Fig. 1). Each receptor was tuned to a specific sound frequency. For sound frequencies below this characteristic frequency the roll-off in sensitivity decreased from 20–30 dB/octave to 10–15 dB/octave as the characteristic frequency of receptors increased from 3–11 kHz (Fig. 4A). For each individual receptor the slope, dynamic range and maximum spike response were similar for different sound frequencies (Fig. 9A). The receptors were tonotopically organized with the characteristic frequency of the receptors increasing from the proximal to the distal end of the array (Figs. 5, 6). Several receptors had characteristic frequencies of 5 kHz. These receptors were divided into two groups on the basis of their maximum spike response produced in response to pure tones of increasing intensity (Fig. 7). Independent of the tuning of the receptor no two-tone inhibition was observed in the periphery, thus confirming that such interactions are a property of central integration.
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  • 5
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intact and one-eared crickets,Gryllus bimaculatus, were tested for phonotactic behavior in a closed-loop and an open-loop situation and for related physiological characteristics of an identified auditory neuron pair, the left and the right AN2. Intact animals that performed phonotaxis in the closed-loop condition showed intended turning tendencies in the open-loop condition that correlated with the directional characteristics of their AN2s (Figs. 1–3). Animals in which one foreleg had been amputated during postembryonic development (one-eared regenerates) were classified according to their phonotactic performance as tracking or unoriented animals. The ability of one-eared regenerates to track a sound source was closely correlated with the direction of turning tendencies in the open-loop behavior and to specific features of their AN2 pair (Figs. 4–6). Some animals with one foreleg amputated as adults (one-eared amputees) perform stable phonotactic walking. Their open-loop behavior, however, is different from that of the tracking one- eared regenerates (Fig. 7). One-eared amputees showed stable phonotactic walking when calling song was presented from above and the sound intensity was varied according to the actual walking angle of the animal. The only orientational cue under this condition is the difference of sound intensity at different walking directions (Figs. 8–11). Different mechanisms are discussed for sound localization in one-eared regenerates and one- eared amputees based on turning tendencies which depend on the instantaneous stimulus intensity or on the intensity change between successive stimuli.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1351
    Keywords: Directional hearing ; Medial septum ; Cricket auditory system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In the cricket Gryllus bimaculatus, it is demonstrated that the medial septum in the prothoracic trachea of the auditory system plays an important role in shaping the directional sensitivity of the ear. After perforation of the medial septum, the directional characteristic of intact animals, showing a mean right-to-left difference in sensitivity of 14 dB, becomes more omnidirectional with a mean right-to-left difference of only 7 dB. Correspondingly, the rate of change in auditory sensitivity for a sound source moving from frontal to contralateral is reduced to 0.78 dB/10° versus 1.5 dB/10° in intact animals (Figs. 2, 3). A computer simulation of phonotaxis based on these findings predicts a reduction in phonotactic performance in animals with a perforated septum. This prediction is in good quantitative agreement with experimental data (Fig. 4) and emphasizes the importance of an intact septum for effective phonotaxis in crickets.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0097-8485
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 75 (1989), S. 425-432 
    ISSN: 1432-2234
    Keywords: Lower bounds ; MCSCF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A MCSCF-method for minimization of the variance yielding an optimal basisset of variance minimizing orbitals in analogy to Löwdin's natural orbitals for minimal energy is developed.
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  • 9
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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