Auditory midbrain responses parallel spectral integration phenomena

Resolving the frequency components of complex sound spectra including speech is an inherent, important accomplishment of the auditory nervous systems of vertebrates. The critical perceptual unit in the frequency domain, the critical bandwidth, has a simple functional equivalent within the principal midbrain auditory nucleus--the central nucleus of the inferior colliculus.     

Sex pheromones in snakes

The majority of pheromones identified to date are insect pheromones, which are volatile in nature. Identification of nonvolatile pheromones have been relatively rare, especially in vertebrates. Male and female garter snakes use pheromones to mediate sexual behavior. The female sex attractiveness pheromone of the Canadian red-sided garter snake, Thamnophis sirtalis parietalis, consists of a novel series of nonvolatile saturated and monounsaturated long-chain methyl ketones, whereas the male sex recognition pheromone contains squalene. These compounds were isolated, identified, and partially synthesized, and field tests show them to be biologically active.     

Retinal projections in blind snakes

Following unilateral enucleation of blind snakes, serial sections of the brains were stained by the Fink-Heimer procedure; the sections revealed terminal degeneration in the lateral geniculate nucleus of the thalamus bilaterally, nucleus posterodorsalis of the pretectum bilaterally, and superficial layers of the contralateral optic tectum. The stained degenerating fibers in the tectum were considerably less dense than in the thalamus.     

Auditory responses in avian vocal motor neurons: a motor theory for song perception in birds

The hypoglossal motor neurons that innervate the vocal organ (syrinx) of the male zebra finch show a selective, long-latency (50-millisecond) response to sound. This response is eliminated by lesions to forebrain song-control nuclei. Different song syllables elicit a response from different syringeal motor neurons. Conspecific vocalizations may therefore be perceived as members of a set of vocal gestures and thus distinct from other environmental sounds. This hypothesis is an avian parallel to the motor theory of speech perception in humans.     

Behavior and phylogeny: constriction in ancient and modern snakes

Comparative analyses of behavior have an underappreciated potential for revealing the role of ethoecological factors in the origins of higher taxa. Twenty-seven species (13 genera) in the advanced family Colubridae exhibited 19 patterns of coil application; one or two patterns were usually consistent within a genus. Forty-eight species (26 genera) in the primitive families Acrochordidae, Aniliidae, Boidae, and Xenopeltidae usually used a single pattern, despite differences in age, size, shape, habitat, and diet. This implies the shared retention of an action pattern used by their common ancestor no later than the early Paleocene. Constriction must have been used as a prey-killing tactic very early in the history of snakes and might have been a behavioral "key innovation" in the evolution of their unusual jaw mechanism.     

Unilateral Increase of Auditory Sensitivity following Early Auditory Exposure

A 30-second exposure (priming) to a loud noise induced a long-lasting susceptibility to audiogenic seizures and a 15-decibel decrease in threshold to the Preyer acoustic startle reflex in C57BL/6J mice. Both effects were absent when the subjects were primed in one ear and subsequently tested in the contralateral ear. It was postulated that the primary effect of priming is an increase in auditory sensitivity due to changes in the ear itself or in those parts of the auditory system which receive their input exclusively from one ear.     

Axial differences in the musculature of uropeltid snakes: the freight-train approach to burrowing

The shield-tailed snakes (family Uropeltidae) extend and widen the tunnels in which they live by alternately curving and straightening the anterior portion of their vertebral columns within the skin, a burrowing method that proves to be most effective for tunneling amid roots and rocks, as well as for producing tunnels wider than the trunk through unpredictably heterogeneous substrates. The muscles of the anterior portion of the uropeltid trunk are larger and thicker than those of the posterior and are further modified by the inclusion of large amounts of myoglobin, numerous mitochondria, and diverse other ultrastructural and enzymatic specializations, which presumably represent adaptations for sustained work loads. The very much thinner, serially homologous, but unmodified musculature of the posterior trunk occupies only a much smaller fraction of the cross-sectional area. This regional modification increases the effectiveness of the posterior body for storing viscera and developing embryos.     

模式可调智能振动压路机动力学特性的建模与仿真

分析了智能振动压路机多模式调整原理;并根据其结构特点,提出一种基于水平振荡和垂直振动的整体动力学模型.以XG6133D型智能压路机为例,研究了压实进程中振动轮、机架在多模式下及减振系统参数发生变化时的动力学响应特性.仿真结果表明,在压实进程中应主动控制减振器参数和调整激振模式,以提高压实效率及改善驾驶舒适性.     

Mathematical modeling of the process of vibratory lifting of sugar beet roots

A calculation mathematical model of the process of vibratory lifting of sugar beet roots is constructed. The root is modeled as a solid, and the vibrating lifting implement vibrates in the longitudinal vertical plane.     

浙江重点蛇类资源数量与生态分布研究

采用系统抽样技术和样带法,对浙江12个重点蛇种的数量和生态分布进行了研究.初步查清了这12个蛇种在其分布区范围的种群出现密度和种群资源量,分别为:赤链蛇,2.97条/km2,60.47×104条;王锦蛇,4.57条/km2,93.05×104条;玉斑锦蛇,0.39条/km2,7.94×104条;黑眉锦蛇,0.83条/km2,33.80×104条;赤峰锦蛇,5.09条/km2,0.36×104条;灰鼠蛇,1.04条/km2,21.17×104条;滑鼠蛇,0.74条/km2,15.07×104条;乌梢蛇,4.08条/km2,83.07×104条;银环蛇,1.35条/km2,41.23×104条;眼镜蛇,2.80条/km2,57.01×104条;五步蛇,1.40条/km2,27.96×104条;蝮蛇,4.37条/km2,63.10×104条.生态分布的统计研究表明:在小地形类型上,下坡和山谷地带蛇类数量最多,主要为王锦蛇、灰鼠蛇、滑鼠蛇、乌梢蛇、眼镜蛇和五步蛇;平地上次之,主要是赤链蛇、蝮蛇和银环蛇;黑眉锦蛇和玉斑锦蛇在平地与下坡及山谷地带分布数量不相上下.在小生境类型上,以灌草丛上蛇类最多,主要是眼镜蛇、滑鼠蛇、五步蛇和黑眉锦蛇;农田和旱地次之,主要为赤链蛇、灰鼠蛇和银环蛇;再是园地和乔木林,玉斑锦蛇主要在园地,五步蛇集中分布在灌草丛和乔木林;乌梢蛇和王锦蛇在上述生境均有分布,在灌草丛上稍占优势;蝮蛇则多见于农田、旱地、园地和灌草丛.文末,提出了如何保护好浙江蛇类资源的对策和建议.     

Auditory habituation and barbiturate-induced neural activity

The finding that barbiturates abolish habituation decrements in auditory evoked potentials has been interpreted as being caused by removal of the influence of the reticular formation. Similar changes in the medial geniculate are produced by barbiturates without any intervening habituation, suggesting that refractory processes have been confused with habituation.     

Auditory sense in certain sphingid moths

Moths of the genus Celerio, hovering and feeding from blossoms, have been observed to react vigorously to high-pitched sounds. The acoustic receptor appears to involve the labial palps. Its characteristics have been determined from responses made, when the moth is exposed to artificial sound pulses, by an interneuron originating in its head. These responses have been found only in 4 out of 19 sphingid species tested.     

Auditory system of noctuid moths

Insect-eating bats find their aerial food by sonar, through emitting ultrasonic chirps and locating sources of echoes. Certain moths have ears sensitive to these chirps and can detect bats well beyond the range of the bats' sonar. On hearing a distant bat, many moths turn and fly directly away from the source of ultrasound. Only one sense cell in each ear of a moth provides the primary nervous information for this response. This article describes my initial attempts to find out how a moth's central nervous system processes the train of chirps reaching its two ears. The ear of a restrained moth is exposed to a sequence of artifically generated ultrasonic pulses that approximates the cries made by a bat. This stimulus can be varied with respect to ultrasonic frequency (pitch), pulse intensity, pulse duration, the interval between pulses, and pulse-train duration. The more sensitive acoustic sense cell responds to all frequencies between about 15,000 and 80,000 cycles per second, but the signal that it transmits to the moth's central nervous system contains no measure of frequency within this range. However, this nerve signal reports variations in the other parameters of the stimulus. The acoustic fiber connects, in the central nervous system, with various nerve cells that transform the signal farther. The signal from a pulse-marker neuron contains no measures of pulse intensity or pulse duration, reporting only changes in interpulse interval and pulse-train duration. A train-marker neuron reports only the duration of the pulse train. The stimulus parameters may be likened to keys, each of which is necessary to gain admittance through a given door but becomes superfluous once this door has been passed. This analogy suggests one of the ways in which a signal is transformed in its passage through the nervous system, and how its specificity is assured in eliciting a given response. In addition to undergoing this kind of transformation, neural signals generated in the two directionally sensitive ears must be combined if a flying moth is to steer a course away from a distant bat. Neurons have been discovered in the central ganglia which summate signals from the right and left ears. Other neurons are inhibited in their activity by stimulation of one ear. The moth may combine signals from these neurons with motor-nerve information on the attitude of its own wings, which act as oscillating baffles modifying its directional acoustic sensitivity 20 to 40 times a second as it flaps an erratic path through the darkness.     

Auditory intensity discrimination at high frequencies in the presence of noise

Over a wide range of intensities, subjects were able to detect small differences in the intensity of a high-frequency band of noise that was presented with a relatively intense, complementary band-reject noise. This indicates that neither of two possible mechanisms for peripheral intensity coding, those based on timing and on spread of excitation, is necessary for the large dynamic range of human hearing. It is shown that the information available in the firing rate of a small number of nerve fibers can account for these data.     

Auditory thresholds in the rat measured by an operant technique

An adaptation of the Ratliff and Blough technique has been developed for auditory measurement in rats. Thresholds for a 2000-cy/sec tone were determined over a period of weeks. Kanamycin, an ototoxic agent, was then administered, and the gradual rise in threshold was followed.     

空间抛物面状通讯天线振动模态浓缩现象分析

应用摄动理论分析了空间大型抛物面状通讯天线振动模态发生“浓缩”现象的机理．这类天线属于对质量缺陷很敏感的周期对称性结构，这种结构具有高密度（近频）模态，当近频模态发生联合使结构内部振动发生“浓缩”现象时，强烈的振动被“浓缩”到天线结构中某一小区域．研究结果表明，具有大量弱联子结构的天线当其肋架质量存在缺陷后容易激起模态“浓缩”现象．以８肋架天线为计算机模拟计算模型验证了分析结果的正确性．对影响天线结构模态“浓缩”现象的结构参数也作了分析讨论．     

Hinged teeth in snakes: an adaptation for swallowing hard-bodied prey

Six genera of snakes, representing at least three lineages, possess teeth that fold backward against the jaws rather than being firmly ankylosed. This condition, effected by a connective tissue hinge at the base of each tooth, is associated with suites of cephalic modifications that enable the snakes to grasp and to swallow hard-bodied prey.