东方蝙蝠在交通噪声环境中的回声定位行为

环境噪声会降低动物声信号可探测性,是动物声信号进化的压力。为了避免人工噪声干扰,多数脊椎动物调整其叫声的频谱-时间结构,如采用延长叫声持续时间、提高频率和增加强度等策略。本研究选择回声定位声波频率范围与交通噪声频率范围相互重叠的东方蝙蝠(Vespertilio sinensis)为研究对象,在自然条件下开展实验,研究交通噪声对蝙蝠回声定位声波的影响。本实验选择交通噪声强度存在差异的两个样点,分别录制东方蝙蝠的回声定位声波,分析其结构参数。在交通噪声强度较高的样点,东方蝙蝠回声定位声波的持续时间、斜率均未显著改变,但起始频率、主频、终止频率及带宽均显著提高。结果表明,东方蝙蝠的回声定位行为在交通噪声干扰下具有明显的可塑性。     

蝙蝠回声定位声波的可塑性及其生态适应

蝙蝠通过调节回声定位声波特征来满足自身的感官需求,表现出回声定位声波的可塑性及其对生态环境与需求的适应。声波频率、强度、脉冲持续时间和间隔时间等特征与蝙蝠所处的生态位密切相关,声波可塑性在蝙蝠进化过程中起着至关重要的作用。本文结合马铁菊头蝠(Rhinolophus ferrumequinum)和大趾鼠耳蝠(Myotis macrodactylus)回声定位声波可塑性的研究,从回声定位声波的方向性、目标距离、环境复杂度和应对干扰4个方面总结了蝙蝠如何通过改变回声定位声波特征来满足自身在导航和捕捉猎物过程中的感官需求与生态适应,并阐述了回声定位声波可塑性的研究现状,为开展蝙蝠声学和行为学研究提供参考。     

综述与专论: 蝙蝠，听觉和回声定位研究的模型动物

科学家以蝙蝠为模式动物,从听觉、回声定位和生态适应与演化等方面开展了研究,取得了令人瞩目的成果。为适应回声定位,蝙蝠听觉系统的结构和功能产生了明显的特化。从外周到中枢形成了对声频率极为有序的表征,甚至在恒频-调频（constant frequency-frequency modulation,CF-FM）蝙蝠耳蜗形成了所谓的听觉凹,以及听皮质功能组构也模块化,成为了具有代表性的特化象征。神经元反应的潜伏期对蝙蝠不仅是基本特性,也是回声定位行为调控的一部分;研究发现,有较长潜伏期的神经元具有较尖锐的回声-延迟调谐特性,而较短潜伏期的神经元则有较宽的回声-延迟调谐特性。蝙蝠听神经元对频率调谐的精准度亦远胜于人类和其他非回声定位动物;而且,源于耳蜗听觉凹的传入在各级听中枢均显示出对回声定位信号第二谐波CF成分的过度表征,以满足对靶物回声多普勒频移探测的需要。时程是回声定位蝙蝠发声信号主动改变的参数之一,而时程调谐神经元则提供了一种编码声音时相特征的重要神经机制,匹配了对回声定位信号时相信息加工的需要。在多种回声定位蝙蝠的听中枢还发现,有回声-延迟调谐神经元,它们不仅能对靶物距离进行调谐,而且...     

调频蝙蝠用回声分类区分植物的神经生理机制研究进展

回声定位蝙蝠具有利用回声定位系统来完成对靶物探测、定位和分类等任务的能力。在这三类基本任务中,关于蝙蝠如何对靶物进行分类的研究起步较晚,且先前的研究大多集中在对简单靶物的分析。然而,蝙蝠接收的绝大部分回声来自复杂的物体,这种回声是必须借助统计学方法描述的复杂回声。近年来,有关调频蝙蝠对从植物返回的复杂回声的分类研究取得了一些重要进展,本文对调频蝙蝠利用回声分类区分植物的行为学证据、分类线索、相关的分类模型以及基于不同分类线索下的神经基础作简要介绍和评述,以期为相关研究人员提供参考。     

高度杂波空间中 CF-FM 蝙蝠下丘回声定位的神经机制

蝙蝠是回声定位的专家。对于在高度杂波空间中捕食的CF-FM蝙蝠,面临着如何从发声和众多由背景环境物体反射的杂波回声中分辨和判断来自靶物的回声所携带信息的问题。已有研究表明,CF-FM蝙蝠可通过发出复杂成分的声脉冲,并通过听中枢的时相和频率整合来处理杂波环境下发声-回声对中包含的靶物距离和相对移动速度的信息。就以上方面在听中脑下丘的神经机制进行概述,以促进人们对听中枢在复杂听环境下对回声定位信号加工原理的认识。     

环境噪声对蝙蝠回声定位叫声及飞行活动的影响

环境噪声影响动物的活动及其叫声特性,已成为动物面对的一种重要选择压力。为应对噪声的干扰,多数动物类群会远离噪声区域和改变其叫声的频谱时间结构,如延长叫声持续时间、提高叫声频率等,但有些动物的活动和叫声频谱时间结构并不受环境噪声的影响。本研究在自然条件下,研究不同环境噪声强度对蝙蝠活动和回声定位声波的影响。选取噪声强度有差异的12个样点,分别录制各样点大卫鼠耳蝠、西南鼠耳蝠、亚洲长翼蝠及未知蝙蝠的回声定位声波,分析其持续时间、起始频率、峰频、终止频率和带宽,统计蝙蝠通过次数。回归分析结果显示：环境噪声强度与大卫鼠耳蝠、西南鼠耳蝠、亚洲长翼蝠及未知蝙蝠的活动无显著相关性P > 0.05）,与回声定位声波的脉冲持续时间、起始频率、峰频、终止频率及带宽均不显著相关（P > 0.05）。暗示低频低强度（< 20 kHz, < 67.5 dB）的环境噪声可能对高频回声定位蝙蝠的叫声及活动没有显著影响。     

降雨噪声对菲菊头蝠出飞行为的影响

降雨噪声属于常见的自然噪声,由雨滴撞击物体表面产生。目前,有关降雨噪声对动物的潜在影响被普遍忽视。回声定位蝙蝠主要利用声信号在黑暗环境导航空间、探测猎物及社群交流,是开展降雨噪声影响研究的理想类群。本研究选择菲菊头蝠 (Rhinolophus pusillus)作为研究对象,检验降雨噪声是否影响蝙蝠出飞行为。我们在集群栖息地外,播放强降雨噪声、空白对照和种内回声定位声波,开展野外回放实验。利用单因素方差分析及其事后检验,评价菲菊头蝠对不同回放刺激的反应差异。研究发现,相比空白对照,强降雨噪声导致菲菊头蝠的通勤数量百分比平均降低2.82倍,回声定位脉冲数量平均减少4.86倍,集群出飞时间延长3.75 min。相比空白对照,同种回声定位声波对菲菊头蝠出飞行为的影响并不显著。研究结果证实强降雨噪声抑制菲菊头蝠的出飞行为。本研究表明,降雨引起 的噪声干扰可能是导致蝙蝠躲避降雨的重要因素,为野生蝙蝠物种保育与管理提供启示。     

蝙蝠回声定位与捕食对策的研究

蝙蝠的回声定位可以在相当程度上反映出其捕食对策以及栖息环境的特点,回声定位在强度、持续时间及频率等方面的变化模式显示出这类声学信号的多样性,而这种多样性与蝙蝠的捕食对策相关。这方面的研究在国际上历经几十年不衰,然而,在我国,蝙蝠回声定位的研究基本上是空白?..     

普氏蹄蝠下丘谐波内外神经元处理多普勒频移补偿信息的差异

为了探讨普氏蹄蝠下丘神经元在处理多普勒频移补偿后回声定位信号中的作用,实验采用双声刺激模式模拟蝙蝠不同飞行状态下产生多普勒频移补偿后的脉冲-回声对,即发声频率改变,回声频率维持恒定的情况下,研究下丘神经元对不同补偿值下的回声反应恢复率.结果发现:根据神经元在某一补偿值下对回声信号反应的恢复率是否超过70%,可将其分为具有选择性(S)和无选择性(NS)的两类神经元.且谐波内S神经元所占比例(68%)远超过非谐波内S神经元(39%).分析神经元的发放模式发现谐波内S神经元中相位型发放模式比例(44.3%)明显高于其他三种类型神经元.另外,虽然S和NS神经元的强度-潜伏期函数类型均以饱和型为主,但谐波内S神经元强度-潜伏期函数的最佳强度(best amplitude,BA)(95.3±14.0)dB SPL低于NS神经元的BA(104.1±10.2)d B SPL(P0.01),同时也低于非谐波内S神经元的BA(109.7±7.9)dB SPL(P0.01).以上实验结果表明,在下丘水平,神经元就已对多普勒频移补偿后回声定位信号的处理有了分工,集中在谐波内的S神经元通过提高对某一补偿值下回声信号反应的恢复率实现,对回声信息的精确编码,避免其他杂波干扰信息.同时,谐波内S神经元的发放模式和强度-潜伏期函数特点也满足其在复杂环境中精确声学成像的需求.     

蝙蝠声音信号功能研究进展

声音信号介导动物的资源竞争、配偶选择及反捕食等系列生活史事件,对维持动物种群稳定与群落平衡至关重要。蝙蝠占据夜空生态位,视觉退化,听觉发达,一直被视为声学研究的模式生物。本文围绕蝙蝠回声定位声波与交流声波的功能,综述当前研究现状,展望未来发展方向。纵观已有研究,蝙蝠回声定位声波具有多重功能,包括空间导航与猎物探测、水体与植被识别、协调觅食活动及传递交流信息。蝙蝠利用交流声波从事社群活动,包括社群联系、资源防御、繁殖活动及求救呼叫。绝大多数研究关注蝙蝠回声定位声波的功能,有关蝙蝠交流声波的功能近年才引起重视。未来工作有待进一步探究蝙蝠声音信号产生的影响机制。     

Preference of a revolving target to a stationary one by the big brown bat, Eptesicus fuscus

Utilizing a three-ramp platform, we studied the detection of a revolving and a stationary target in the presence of background clutter by trained Eptesicus fuscus. During the test, the mean amplitude of echo from either target was always larger than that of the background echoes at the bat-to-target distance of 30, 70 and 100 cm. The amplitude of the echo reflected back from a revolving target was modulated between a maximum and a minimum value. An electric motor was used to revolve a target. The frequency contents of the motor noise were mostly below 1 kHz. While the total percent response of approaching either target is always more than 90% at every bat-to-target distance tested, the bats approach a revolving target more frequently than a stationary one. Echolocation pulses emitted by the bats during the test were recorded and analyzed. The bats shortened their pulse durations and interpulse intervals and lowered the frequency contents as they entered into the crawling phase from the searching phase. Potential interference of background echoes and ambient noise with the performance of the bats is discussed. The preference of a revolving target to a stationary one by the bats is perhaps due to the fact that a revolving target has a higher releasing value than a stationary one does.     

Regulation of vocal amplitude by the blue-throated hummingbird, Lampornis clemenciae

Animals that rely on vocal communication must broadcast sound so that a perceptible signal is transmitted over an appropriate distance. We found that male blue-throated hummingbirds modified the amplitude of their vocalizations in response to both naturally occurring and experimenter-controlled changes in ambient noise levels. This phenomenon is known as the Lombard effect and may increase the efficiency of acoustic signalling. This study demonstrates the effect under natural field conditions and documents the first hummingbird species (Apodiformes: Trochilidae) to show this behaviour. We measured sound pressure levels (SPLs) of Serial Chip territorial advertisement calls across a natural range of ambient noise, primarily due to creeks within male territories. We found a significant correlation between the amplitude of Serial Chips and the amplitude of background noise. To test this relationship, we broadcast recordings of creek noise at high and low amplitudes while target individuals were producing Serial Chip vocalizations. We measured vocal SPLs before and during the playback. Individuals responded to changes in playback creek noise by changing the amplitude of Serial Chip production. We also measured transmission properties of Serial Chip calls through natural habitat to calculate the approximate amplitude of vocalizations at the position of the calling bird. We suggest that amplitude regulation of vocalizations contibutes to signal transmission distance along with the established relationships between singing behaviour, acoustic structure and habitat. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.     

Changes in the amplitude and direction of goal-directed hand movements in the lack of visual information

The goal of the present investigation was to determine the precision of goal-directed hand movements in the lack of visual information. The movement amplitude and direction was examined under different experimental conditions. Subjects were ten female and ten male university students. The motor test was drawing 10 cm long straight line and 24 cm long zigzag line in four different experimental conditions. 1) The drawing with open eyes was followed immediately with drawing with closed eyes. 2) The drawing was executed from memory in the lack of visual information. 3) Drawing with restricted amplitude or direction. 4) Drawing with verbal feedback. The errors of the target distance and the lateral deviations from the target were different under the different experimental conditions. The largest errors and underestimation of the target distance occurred in drawing horizontal straight line with closed eyes. No statistically significant gender differences were found. It is concluded that the practice, adjustment of single movement parameter to the target, and the verbal feedback assist better the accuracy of unseen goal-directed hand movement than the recent visual memory.     

Effects of noise bandwidth and amplitude modulation on masking in frog auditory midbrain neurons

Natural auditory scenes such as frog choruses consist of multiple sound sources (i.e., individual vocalizing males) producing sounds that overlap extensively in time and spectrum, often in the presence of other biotic and abiotic background noise. Detection of a signal in such environments is challenging, but it is facilitated when the noise shares common amplitude modulations across a wide frequency range, due to a phenomenon called comodulation masking release (CMR). Here, we examined how properties of the background noise, such as its bandwidth and amplitude modulation, influence the detection threshold of a target sound (pulsed amplitude modulated tones) by single neurons in the frog auditory midbrain. We found that for both modulated and unmodulated masking noise, masking was generally stronger with increasing bandwidth, but it was weakened for the widest bandwidths. Masking was less for modulated noise than for unmodulated noise for all bandwidths. However, responses were heterogeneous, and only for a subpopulation of neurons the detection of the probe was facilitated when the bandwidth of the modulated masker was increased beyond a certain bandwidth - such neurons might contribute to CMR. We observed evidence that suggests that the dips in the noise amplitude are exploited by TS neurons, and observed strong responses to target signals occurring during such dips. However, the interactions between the probe and masker responses were nonlinear, and other mechanisms, e.g., selective suppression of the response to the noise, may also be involved in the masking release.     

Relative motion parallax and target localisation in the locust,Schistocerca gregaria

Summary This paper addresses two questions. 1. Does Schistocerca gregaria detect edges which are defined solely by velocity-contrast, that is by the difference in the image speeds generated by an object and its background when the locust moves? 2. Is the locust's ability to measure the distance of a target by motion parallax independent of the relative motion between target and back-ground?A locust walking on a circular platform was surrounded by a stationary cylinder which was lined with an irregular texture. Against this background, the insect viewed 3 stationary, equidistant targets. One target was black, one grey and the last was textured like the cylinder. Peers and jumps were aimed preferentially at the textured and black targets showing that targets can be detected by virtue of their velocity-contrast with the background. When textured targets were wide, jumps were seen to be aimed at the targets' edge.To assess whether velocity-contrast between target and background distorts distance-estimates, we used jump-velocity as a measure of apparent distance and examined how it varied with different arrangements of target and background. When a textured background is close to a target or the target is very wide, velocity contrast is small. The locust's jump-velocity is then 10% greater than when velocity-contrast is increased by making the background distant or the target narrow. This suggests that the locust is efficient at separating signals encoding absolute motion from those encoding relative motion.     

Auditory aftereffects of approaching and withdrawing sound sources: Dependence on the trajectory and location of adapting stimuli

Perception of approaching and withdrawing sound sources and their action on auditory aftereffects were studied in the free field. Motion of adapting stimuli was mimicked in two ways: (1) simultaneous opposite changes of amplitude of broadband noise impulses at two loudspeakers placed at 1.1 and 4.5 m from the listener; (2) an increase or a decrease of amplitude of broadband noise impulses in only one loudspeaker, the nearer or the remote one. Motion of test stimuli was mimicked in the former way. Listeners determined direction of the test stimuli motion without any adaptation (control) or after adaptation to stationary, slowly moving (with an amplitude change of 2 dB) and rapidly moving (amplitude change of 12 dB) stimuli. Percentages of “withdrawal” reports were used for construction of psychometric curves. Three phenomena of auditory perception were observed. In the absence of adaptation, a growing-louder effect was revealed, i.e., listeners reported more frequently the test sounds as the approaching ones. Once adapted to stationary or slowly moving stimuli, listeners showed a location-dependent aftereffect. Test stimuli were reported as withdrawing more often as compared with control. The effect was associated with the previous one and was weaker when the distance to the loudspeaker producing adapting stimuli was greater. After adaptation to rapidly moving stimuli, a motion aftereffect was revealed. In this case, listeners reported a direction of test stimuli motion as being opposite to that of adapting stimuli. The motion aftereffect was more pronounced when the adapting stimuli motion was mimicked in the former way, as this method allows estimation of their trajectory. There was no relationship between the motion aftereffect and the growing-louder effect, whichever way the adapting stimuli were produced. There was observed a tendency for reduction of aftereffects of approaching and for intensification of aftereffects of withdrawal with growing distance from source of adapting stimuli.     

Discrimination performance and echolocation signal integration requirements for target detection and distance determination in the CF/FM bat,Noctilio albiventris

Summary Bats of the speciesNoctilio albiventris were trained to detect the presence of a target or to discriminate differences in target distance by means of echolocation. During the discrimination trials, the bats emitted pairs of pulses at a rate of 7–10/s. The first was an 8 ms constant frequency (CF) signal at about 75 kHz. This was followed after about 28 ms by a short-constant frequency/ frequency modulated (short-CF/FM) signal composed of a 6 ms CF component at about 75 kHz terminating in a 2 ms FM component sweeping downward to about 57 kHz. There was no apparent difference in the pulse structure or emission pattern used for any of the tasks. The orientation sounds of bats flying in the laboratory and hunting prey under natural conditions follow the same general pattern but differ in interesting ways.The bats were able to discriminate a difference in target distance of 13 mm between two simultaneously presented targets and of 30 mm between single sequentially presented targets around an absolute distance of 35 cm, using a criterion of 75% correct responses.The bats were unable to detect the presence of the target or to discriminate distance in the presence of continuous white noise of 54 dB or higher SPL. Under conditions of continuous white noise, the bats increased their pulse repetition rate and the relative proportion of CF/FM pulses.The bats required a minimum of 1–2 successive CF/FM pulse-echo pairs for target detection and 2–3 to discriminate a 5 cm difference in distance. When the distance discrimination tasks were made more difficult by reducing the difference in distance between the two targets the bats needed to integrate information from a greater number of successive CF/FM pulse-echo pairs to make the discrimination.Abbreviations CF constant frequency - FM frequency modulation     

Perception of approaching and withdrawing sound sources after exposure to broadband noise: The importance of spatial domain

The existence of space-specific differences in auditory aftereffects has been tested under short-term (5 s) exposure to broadband noise (20–20000 Hz). Adapting stimuli were emitted as constant-amplitude noise sequences. Test stimuli could be of constant and changing amplitude: increasing amplitude of noise pulses in a sequence mimicked an approaching sound source, whereas a decrease in amplitude was perceived as withdrawal. The experiments were done in an anechoic chamber. Auditory aftereffects were assessed under the following conditions: (a) adapting and test stimuli were emitted through a loudspeaker mounted at a distance of 1.1 m from the listener (i.e., subjectively near); (b) both stimuli were emitted from a distance of 4.5 m (subjectively far); (c) adapting and test stimuli were emitted from different distances. The results showed that the characteristics of perception of the imitated sound source motion were similar in proximity and remoteness, which was observed both in the control (without adaptation) and after adaptation to noise. In the absence of adaptation, the psychophysical curves were asymmetrical: the listeners reported approaching of test stimuli more often for both spatial domains. However, the overestimation of test stimuli as drawing closer was more pronounced when they were emitted from the distance of 1.1 m, i.e., from near the listener. After the adaptation to noise, the aftereffects showed spatial specificity and were observed only when adapting and test stimuli belonged to the same spatial domain. These aftereffects were similar in their pattern and strength both in proximity and remoteness: the listeners reported withdrawal of test stimuli more frequently as compared with the control. As a result of these aftereffects, the symmetry of psychometric curves was restored, and the estimation of the direction of sound source motion in the experiment became equiprobable.     

Collinear interactions and contour integration

The visibility of a local target is influenced by the global configuration of the stimulus. Collinear configurations are a specific case in which facilitation or suppression of the target has been found to be dependent on the contrast threshold of the target. The role of collinear interactions in perceptual grouping, especially in contour integration, is still controversial. In the current study, the role of collinear interactions in noise was investigated using experimental conditions similar to those utilized in studies of contour integration. The contrast detection paradigm in the presence of similar Gabor elements presented in the background was used. The results show that contrast detection threshold of the target alone is increased (suppression) when it is embedded in randomly oriented background elements. However, when the target is flanked by two collinear Gabor elements, the target is facilitated even at higher target contrast levels. Facilitation is not found for orthogonal configurations. The results suggest that the response to a local element in a contour is modified by lateral facilitative and suppressive inputs from elements comprising the smooth contour and randomly oriented background elements, respectively. Thus, detection of elements along a contour should be considered as integration of global neuronal activity rather than as the output of local and individual neurons.     

背景噪声对人感知声音时间信息的影响

对声音时间信息的分辨在人和动物感知声音信息的过程中至关重要.在自然声环境中,声音信息总处于一定的噪声背景下.文章以间隔探测阈值为指标测定了人对纯音和噪声的间隔探测阈值,以及持续噪声背景对间隔探测阈值的影响.声音信号采用1000～10000 Hz的纯音信号和白噪声信号,声音强度为70 dB SPL.背景噪声为持续白噪声,强度分别为45、55、65 dB SPL.结果表明,对纯音信号,随着背景噪声强度增加,间隔探测阈值有升高的趋势.对噪声信号来说,45、55 dB SPL的背景噪声对噪声信号的间隔探测阈值无显著影响,但65 dB SPL的背景噪声使间隔探测阈值显著升高.研究结果提示,背景噪声能够在一定程度上影响人对声音时间信息的感知,影响的程度与背景噪声的强度有关.