Neural inhibition sharpens auditory spatial selectivity of bat inferior collicular neurons

This study examines the role of neural inhibition in auditory spatial selectivity of inferior collicular neurons of the big brown bat, Eptesicus fuscus, using a two-tone inhibition paradigm. Two-tone inhibition decreases auditory spatial response areas but increases the slopes of directional sensitivity curves of inferior collicular neurons. Inferior collicular neurons have either directionally-selective or hemifield directional sensitivity curves. A directionally-selective curve always has a peak which is at least 50% larger than the minimum. A hemifield directional sensitivity curve rises from an ipsilateral angle by more than 50% and either reaches a plateau or declines by less than 50% over a range of contralateral angles. Two-tone inhibition does not change directionally-selective curves but changes most hemifield directional sensitivity curves into directionally-selective curves. Auditory spatial selectivity determined both with and without two-tone inhibition increases with increasing best-excitatory frequency. Sharpening of auditory spatial selectivity by two-tone inhibition is larger for neurons with smaller differences between excitatory and inhibitory best frequencies. The effect of two-tone inhibition on auditory spatial selectivity increases with increasing inhibitory tone intensity but decreases with increasing intertone interval. The implications of these findings in bat echolocation are discussed. Accepted: 18 January 2000     

毛腿鼠耳蝠(Myotis fimbriarus)血液的研究

本文对毛腿鼠耳蝠血液的有形成分和百分比等项正常数值进行了测定,并对各类血细胞的主要形态作了描述。 所测的各项数值与前人报道的数据比较,其红细胞数目和血红素含量都高于同属的其他种,也较其他哺乳动物为高。毛腿鼠耳蝠与该属有些种类的淋巴细胞数目占全部白细胞的百分数最高,也明显高于其他哺乳动物。     

Integration time for short broad band clicks in echolocating FM-bats (Eptesicus fuscus)

Vespertilionid FM-bats (four Eptesicus fuscus and one Vespertilio murinus) were trained in an electronic phantom target simulator to detect synthetic echoes consisting of either one or two clicks. The threshold sound pressure for single clicks was around 47 dB peSPL for all five bats corresponding to a threshold energy of -95 dB re 1 Pa² * s. By varying the interclick interval, T, for double clicks it was shown that the threshold intensity was around — 3 dB relative to the threshold for single clicks at T up to 2.4 ms, indicating perfect power summation of both clicks. A threshold shift of -13.5 dB for a 1 ms train of 20 clicks (0.05 ms interclick interval) confirmed that the bats integrated the power of the stimuli. At T longer than around 2.5 ms the threshold for double clicks was the same as for single clicks. Thus, the bats performed like perfect energy detectors with an integration time of approximately 2.4 ms. This integration time is an order of magnitude shorter than that reported for bats listening passively for pure tones. In our setup the bats emitted sonar signals with durations of 2–3 ms. Hence, the results may indicate that while echolocating the bats integration time is adapted to the duration of the sonar emissions.Abbreviations AGC automatic gain control - FM frequency modulated - peSPL peak equivalent sound pressure level - rms root mean square - SD standard deviation - SE standard error of mean - T interclick interval     

The orientation behaviour of the lesser spearnosed bat, Phyllostomus discolor (Chiroptera) in a model roost

The orientation behaviour of bats (Phyllostomus discolor, Phyllostomidae), flying inside an octagonal roost-like chamber (ø: 100cm; h: 150cm) was examined.It has been shown that the bats begin turning manoeuvres during flight by turning their head towards the direction they intend to proceed to. During early phases of the flights, cumulative navigation errors were evident, indicating that endogenous spatial information plays a major role in the orientation of the bats. During later phases of the flight this error is diminished again. So it can be concluded that the bats start to use exogenous spatial information for orientation while approaching the target.In order to investigate the relative importance of vision, echolocation and endogenous spatial information for approaching the roost, the landing lattices inside the test arena were changed for non-grid dummies. We found that: 1. combined visual and endogenous information are more important than echoacoustical cues, 2. the bats learned quickly to switch their orientation behaviour in order to get a better performance in avoiding the dummies, 3. the learning performance was influenced by the visual similarity of dummies and the real landing lattice.     

Complex sound analysis in the FM bat Eptesicus fuscus,correlated with structural parameters of frequency modulated signals

Big brown bats, Eptesicus fuscus, were presented with artificial frequency modulated (FM) echoes that simulated an object becoming progressively closer to the bat. A stereotyped approach phase behavioral response of the bat to the virtual approaching target was used to determine the ability of the bat to analyze FM signals for target distance information. The degree to which the bats responded with approach phase behavior to a virtual approaching target was similar when they were presented with either a naturally structured artificial FM echo or an artificial FM echo constructed from a series of brief pure tone steps. The ability of the bats to respond to an FM signal structured from a sequence of pure tone elements depended on the number of pure tone steps in the series; the bats required the presentation of tone-step FM signals containing about 83 or greater pure tone elements. Moreover, the duration of the individual tone steps of the tone-step FM signals could not exceed a specific upper limit of about 0.05 ms. Finally, it appears that the bats were able to independently resolve individual tone steps within the tone-step FM signals that were separated by about 450 Hz or more.Abbreviations CF constant frequency - FM frequency modulation     

Complex sound analysis in the lesser bulldog bat: evidence for a mechanism for processing frequency elements of frequency modulated signals over restricted time intervals

A stereotypical approach phase vocalization response of the lesser bulldog bat, 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 bat was not significantly different when presented with naturally structured CF/FM echoes containing FM elements that sweep continuously from about 75-55 kHz in 4 ms or with CF/FM echoes containing FM components constructed from a series of 98 pure tone frequency steps, each with a duration of 0.04 ms. The performance of the bat remained unchanged when the duration of the tone steps was increased up to 0.08 ms but declined sharply to a level that was significantly below that seen with a naturally structured echo when the steps were 0.09 ms or longer. The performance of the bat depended on the duration of the individual tone steps, which could not exceed a specific upper limit of about 0.08 ms. The study suggests that the bats have adaptations for processing individual narrow band segments of FM signals over specific time intervals.Abbreviations CF constant frequency - FM frequency modulation     

Passive sound localization of prey by the pallid bat (Antrozous p. pallidus)

Summary The pallid bat (Antrozous p. pallidus) uses passive sound localization to capture terrestrial prey. This study of captive pallid bats examined the roles of echolocation and passive sound localization in prey capture, and focused on their spectral requirements for accurate passive sound localization.Crickets were used as prey throughout these studies. All tests were conducted in dim, red light in an effort to preclude the use of vision. Hunting performance did not differ significantly in red light and total darkness, nor did it differ when visual contrast between the terrestrial prey and the substrate was varied, demonstrating that the bats did not use vision to locate prey.Our bats apparently used echolocation for general orientation, but not to locate prey. They did not increase their pulse emission rate prior to prey capture, suggesting that they were not actively scanning prey. Instead, they required prey-generated sounds for localization. The bats attended to the sound of walking crickets for localization, and also attacked small, inanimate objects dragged across the floor. Stationary and/or anesthetized crickets were ignored, as were crickets walking on substrates that greatly attenuated walking sounds. Cricket communication sounds were not used in prey localization; the bats never captured stationary, calling crickets.The accuracy of their passive sound localization was tested with an open-loop passive sound localization task that required them to land upon an anesthetized cricket tossed on the floor. The impact of a cricket produced a single 10–20 ms duration sound, yet with this information, the bats were able to land within 7.6 cm of the cricket from a maximum distance of 4.9 m. This performance suggests a sound localization accuracy of approximately ±1° in the horizontal and vertical dimensions of auditory space. The lower frequency limit for accurate sound localization was between 3–8 kHz. A physiological survey of frequency representation in the pallid bat inferior colliculus suggests that this lower frequency limit is around 5 kHz.     

胀果甘草化学成分的研究（Ⅲ）

继前文工作,本文报道从胀果甘草(Glycyrrhiza inflata Bat)根及根茎用95％乙醇渗滤后的提取部分中获得的另外五个化合物的结构鉴定。经理化性质及波谱分析,分别鉴定为胡萝卜甙(Daucosterol)、甘草查尔酮甲(Licochalcone A)、β-谷甾醇(β-Sitosterol),异芒柄花甙(Isoononin)和4＇,7一二羟基黄酮(4＇,7-Dihydroxy-flavone)。其中胡萝卜甙和异芒柄花甙为首次从该植物中获得。药理实验表明,甘草查尔酮甲对H_2O_2诱异的溶血有极好的抑制作用(97.3％),但甘草甙在三个体外氧化体系中都没有明显的活性。