Field-specific responses in the auditory cortex of the unanaesthetized Mongolian gerbil to tones and slow frequency modulations

Responses of multi-units in the auditory cortex (AC) of unanaesthetized Mongolian gerbils to pure tones and to linearly frequency modulated (FM) sounds were analysed. Three types of responses to pure tones could be clearly distinguished on the basis of spectral tuning properties, response latencies and overall temporal response pattern. In response to FM sweeps these three types discharged in a temporal pattern similar to tone responses. However, for all type-1 units the latencies of some phasic response components shifted systematically as a function of range and/or speed of modulation. Measurements of response latencies to FMs revealed that such responses were evoked whenever the modulation reached a particular instantaneous frequency (F_i). Effective F_i was: (1) independent of modulation range and speed, (2) always reached before the modulation arrived at a local maximum of the frequency response function (FRF) and consequently differed for downward and upward sweeps, and (3) was correlated with the steepest slope of that FRF maximum. The three different types of units were found in discrete and separate fields or regions of the AC. It is concluded that gross temporal response properties are one of the key features distinguishing auditory cortical regions in the Mongolian gerbil. Accepted: 13 August 1997     

The role of frequency, phase and time for processing of amplitude modulated signals by grasshoppers

Acoustic signals consist of pressure changes over time and can thus be analyzed in the frequency- or in the time-domain. With behavioural experiments we investigated which frequency components (FC) are necessary for the recognition of the periodic envelope of the conspecific song by females of the grasshopper Chorthippus biguttulus. Further, we determined up to which frequency component phase information is required which would indicate processing in the time domain. Responses of females revealed that signals composed of FC between 10 and 50 Hz are sufficient for recognition of the song envelope. A systematic reduction in the number of FC showed that no single frequency component was required; signals without the fundamental frequency were still highly attractive and only three FC may be sufficient for song recognition. Phase changes for frequencies up to 40 Hz strongly changed the attractiveness of song signals but only little at 50 Hz. Females were also tested with rectangular signals in which pause duration was varied. Evidently, and despite the high attractiveness of song signals with a “missing fundamental”, females evaluated the attractiveness of signals in the time-domain, since the selectivity for pause duration predicted the responses to signals composed from FC well.     

计算听觉侧抑制参数的一种方法

以听觉神经系统信息处理方式为研究对象,根据听觉生理的有关知识提出了一种计算听觉侧抑制参数的方法,并进行了利用所提出的听觉侧抑制参数改善语音频谱的实验。     

Discrimination of wingbeat motion by bats,correlated with echolocation sound pattern

Summary Bats of the species Rhinolophus rouxi, Hipposideros lankadiva and Eptesicus fuscus were trained to discriminate between two simultaneously presented artificial insect wingbeat targets moving at different wingbeat rates. During the discrimination trials, R. rouxi, H. lankadiva and E. fuscus emitted long-CF/FM, short-CF/FM and FM echolocation sounds respectively. R. rouxi, H. lankadiva and E. fuscus were able to discriminate a difference in wingbeat rate of 2.7 Hz, 9.2 Hz and 15.8 Hz, respectively, between two simultaneously presented targets at an absolute wingbeat rate of 60 Hz, using a criterion of 75% correct responses.The performance of the different bat species is correlated with the echolocation signal design used by each species, particularly with the presence and relative duration of a narrowband component preceding a broadband FM component. These results provide behavioral evidence supporting the hypothesis that bats that use CF/FM echolocation sounds have adaptations for the perception of insect wingbeat motion and that long-CF/FM species are more specialized for this task than short-CF/FM species.Abbreviations CF constant frequency - FM frequency modulation     

Harmonic and frequency structure used for echolocation sound pattern recognition and distance information processing in the rufous horseshoe bat

Summary The rufous horseshoe bat, Rhinolophus rouxi, was trained to discriminate differences in target distance. During the discrimination trials, the bats emitted complex FM/CF/FM pulses containing first harmonic and dominant second harmonic components.Loud free running artificial pulses, simulating the CF/FM part of the natural echolocation components, interfered with the ability of the bat to discriminate target distance. Changes in the frequency or frequency pattern of the artificial pulses resulted in systematic changes in the degree of interference. Interference occurred when artificial CF/FM pulses were presented at frequencies near those of the bat's own first or second harmonic components.These findings suggest that Rhinolophus rouxi uses both the first and second harmonic components of its complex multiharmonic echolocation sound for distance discrimination. For interference to occur, the sound pattern of each harmonic component must contain a CF signal followed by an FM sweep beginning near the frequency of the CF.Abbreviations CF constant frequency - FM frequency modulated     

A gating mechanism for sound pattern recognition is correlated with the temporal structure of echolocation sounds in the rufous horseshoe bat

Summary The rufous horseshoe bat, Rhinolophus rouxi, was trained to discriminate differences in target distance. Loud free running artificial pulses, simulating the bat's natural long-CF/FM echolocation sounds, interfered with the ability of the bat to discriminate target distance. Interference occurred when the duration of the CF component of the CF/FM artificial pulse was between 2 and 70 ms. A brief (2.0 ms) CF signal 2–68 ms before an isolated FM signal was as effective as a continuous CF component of the same duration. When coupled with the bat's own emissions, a 2 ms FM sweep alone was effective in interfering when it came 42 to 69 ms after the onset of the bat's pulse. The coupled FM artificial pulses did not interfere when they began during the bat's own emissions.It appears that the onset of the CF component activates a gating mechanism that establishes a time window during which FM component signals must occur for proper neural processing. A comparison with a similar gating mechanism in Noctillo albiventris, which emits short-CF/FM echolocation sounds, reveals that the temporal parameters of the time window of the gating mechanism are species specific and specified by the temporal structure of the echolocation sound pattern of each species.Abbreviations FM frequency modulated - CF constant frequency     

Variance in female responses to the fine structure of male song in the field cricket, Gryllus integer

Although female mating preferences are a focus of current controversy,little detailed information exists on female preferences withinnatural populations. In the field cricket Gryllus integer, malecalls attract sexually receptive females, and females preferentiallymove toward male calls with longer calling bouts (periods ofcalling containing no pause greater than 0.10 s in real time).This study investigated female preferences for other variablesof the male song, including syllable period, chirp pause, andnumber of syllables per chirp. Male song was measured in thefield to determine mean values for each variable in nature.Female preferences were determined using a locomotor-compensatordevice, on which females ran in response to sequential playbacksof synthesized male song. Mean female preferences correspondedroughly to mean male song variables. Nonetheless, females variedgreatly in their responses to synthesized calls differing insyllable period, syllable number, and chirp pause. Moreover,individual females who were more selective for any one variablealso tended to be more selective for others. These results showthat females may differ from one another in their mating preferencesand degrees of selectivity, even within a single population.     

AM representation in green treefrog auditory nerve fibers: neuroethological implications for pattern recognition and sound localization

In addition to spectral call components, temporal patterns in the advertisement-call envelope of green treefrog males (Hyla cinerea) provide important cues for female mate choice. Rapid amplitude modulation (AM) with rates of 250–300 Hz is typical for this species advertisement calls. Here we report data on the encoding of these rapid call modulations by studying the responses of single auditory nerve fibers to two-tone stimuli with envelope periodicities close to those of the natural call. The free-field response properties of 86 nerve fibers were studied from 32 anesthetized males. The accuracy of stimulus envelope coding was quantified using both a Gaussian function fit to the interspike interval histograms derived from the first seven 20-ms stimulus segments, and the vector-strength metric applied to the phase-locked responses. Often, AM encoding in the initial stimulus segment was more faithful than that in its second half. This result may explain why conspecific females prefer calls in which the initial segment is unmasked rather than masked. Both the questions of pattern recognition and localization are discussed, and the data are related to behavioral observations of female choice and localization performance in this species.     

Frequency modulated sound pattern analysis in the lesser bulldog bat: the role of interactions between adjacent frequency elements of complex sounds

A stereotyped approach phase vocalization response of Noctilio albiventris to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bats depended on the temporal pattern of frequency change of the continuously sweeping frequency modulated (FM) component of the signals. When the bats were presented with a CF/FM signal containing a time-reversed upward FM sweep, they responded with approach phase behavior at a performance level that was significantly below that seen with a CF/FM signal containing a naturally structured downward FM sweep. When the FM sweep was divided into a series of brief pure tone steps, the extent to which the bats showed a difference in their capability to process upward versus downward FM sweeps depended on the difference in frequency between the pure tone steps. The bats effectively processed downward but not upward FM sweeps when the difference in frequency between pure tone frequency elements of the FM sweeps was from about 100–200 Hz, but they effectually processed both downward and upward FM sweeps when the tonal elements composing the FM sweeps were separated by more than about 200 Hz. This suggests that the ability of the bats to effectively process downward but not upward FM sweeps is based on local interactions between adjacent frequency elements of the complex sounds.Abbreviations CF constant frequency - FM frequency modulated     

露螽科四种昆虫的核型研究

本文以螽斯精巢为实验材料,经过低渗、固定、压片、空气干燥、Giemsa染色制备染色体标本,对螽斯总科露螽科4种螽斯的核型进行了研究,结果Phaneroptera falcata 2n♂=27, Phaneroptera gracilis 2n♂=25,Ducetia japonica 2n♂=29,Isopsera sp.2n♂=31,均为近端着丝粒染色体,性别决定机制均为XO♂/XX♀型, X染色体为染色体组中最大的染色体。作者认为,Isopsera sp.（2n♂=31）可能是露螽科中较原始的种类,Ducetia japonica(2n♂=29),Phaneroptera falcata (2n♂=27),Phaneroptera gracilis (2n♂=25)可能是由2n♂=31进化来的衔接融合在露螽科染色体进化中起着重要作用。Abstract：Karyotypes of four species belonging to three genera of the Phaneropteridae were investigated.The diploid number of chromosomes is as follows: Phaneroptera falcata species 2n♂=27(XO),Phaneroptera gracilis 2n♂ =25 (XO),Ducetia japonica 2n =29 (XO) and Isopsera sp.2n♂=31(XO) ,all chromosomes are acrocentric,the X chromosomes are the largest members of the sets.It may be assumed that Isopsera sp. 2n♂=31 represents the basic number of chromosomes.The other species,Ducetia japonica 2n♂=29, Phaneroptera falcata 2n♂=27, Ph.gracilis 2n♂=25 could originate 2n♂=31 .Tandem fusions may be important in the karyotype evolution of Phaneropteridae.