Aural representation in the Doppler-shifted-CF processing area of the auditory cortex of the mustache bat

In the mustache bat (Pteronotus pamellii rubiginosus) the frequency and amplitude of an acoustic signal are represented in the coordinates parallel to the surface of the Doppler-shifted-CF (constant frequency) processing area ofthe primary auditory cortex. In this area all cortical neurons studied were excited by contralateral stimuli, and almost all of them were either excited or inhibited by ipsilateral stimuli. These are called E-E (ipsilateral and contralateral excitatory) and I-E (ipsilateral inhibitory and contralateral excitatory) neurons, respectively. The I-E neurons are directionally sensitive, while the E-E neurons are not. The E-E neurons are equally sensitive to echoes between 30 degrees contralateral and 30 degrees ipsilateral. Of the electrode penetrations orthogonal to the Doppler-shifted-CF processing area, 57 percent were characterized by either E-E or I-E neurons. Thus, there are at least two types of binaural columns: E-E columns, mainly located in a ventral part of the Doppler-shifted-CF processing area, where neurons are tuned to weak echoes; and IE columns, mainly distributed in a dorsal part, where neurons are tuned to moderate to intense echoes. Therefore, neurons tuned to weaker echoes integrate or even multiply faint signals from both ears for effective detection of a distant small target, while neurons tuned to moderate to intense echoes are suited for processing directional information and are stimulated when a bat approaches a target at short range. The Doppler-shifted-CF processing area may be considered to consist of two functional subdivisions.     

Cortical computational maps control auditory perception

Mustached bats orient and find insects by emitting ultrasonic pulses and analyzing the returning echoes. Neurons in the Doppler-shifted constant-frequency (DSCF) and frequency-modulated (FM-FM) areas of the auditory cortex form maps of echo frequency (target velocity) and echo delay (target range), respectively. Bats were trained to discriminate changes in echo frequency or delay, and then these areas were selectively inactivated with muscimol. Inactivation of the DSCF area disrupted frequency but not delay discriminations; inactivation of the FM-FM area disrupted delay but not frequency discriminations. Thus, focal inactivation of specific cortical maps produces specific disruptions in the perception of biosonar signals.     

A network model of catecholamine effects: gain, signal-to-noise ratio, and behavior

At the level of individual neurons, catecholamine release increases the responsivity of cells to excitatory and inhibitory inputs. A model of catecholamine effects in a network of neural-like elements is presented, which shows that (i) changes in the responsivity of individual elements do not affect their ability to detect a signal and ignore noise but (ii) the same changes in cell responsivity in a network of such elements do improve the signal detection performance of the network as a whole. The second result is used in a computer simulation based on principles of parallel distributed processing to account for the effect of central nervous system stimulants on the signal detection performance of human subjects.     

Neuroscience. Regional differences in cortical organization

Although there are elegants maps of the human brain that reveal differences in cellular architecture between different cortical regions, there is not much information about how corresponding cortical regions differ between the left and right hemispheres. As Gazzaniga explains in his Perspective, new results reveal the surprising finding of asymmetry in area 22 (which is important for language processing) of the left and right hemisphere (Galuske et al.). Clusters of neurons in area 22 of the left hemisphere are spaced farther apart and have longer axons cabling them together than neuronal clusters in area 22 of the right hemisphere.     

Interhemispheric asymmetries of the modular structure in human temporal cortex

Language-relevant processing of auditory signals is lateralized and involves the posterior part of Brodmann area 22. We found that the functional lateralization in this area was accompanied by interhemispheric differences in the organization of the intrinsic microcircuitry. Neuronal tract tracing revealed a modular network of long-range intrinsic connections linking regularly spaced clusters of neurons. Although the cluster diameter was similar in both hemispheres, their spacing was about 20 percent larger in the left hemisphere. Assuming similar relations between functional and anatomical architecture as in visual cortex, the present data suggest that more functionally distinct columnar systems are included per surface unit in the left than in the right area 22.     

How visual stimuli activate dopaminergic neurons at short latency

Unexpected, biologically salient stimuli elicit a short-latency, phasic response in midbrain dopaminergic (DA) neurons. Although this signal is important for reinforcement learning, the information it conveys to forebrain target structures remains uncertain. One way to decode the phasic DA signal would be to determine the perceptual properties of sensory inputs to DA neurons. After local disinhibition of the superior colliculus in anesthetized rats, DA neurons became visually responsive, whereas disinhibition of the visual cortex was ineffective. As the primary source of visual afferents, the limited processing capacities of the colliculus may constrain the visual information content of phasic DA responses.     

一次局地暴雨天气多普勒雷达的资料分析

在大尺度环流背景条件对暴雨天气无明显指示的环境下,夏季的局地暴雨要关注当地气象要素的分布特征,同时要密切关注新一代天气雷达的回波演变。应用海拉尔天气雷达,从反射率因子、组合反射率因子、垂直累积液态含水量产品以及径向速度产品,分析2007年6月30日12:50～14:00发生在陈旗的巴彦库仁镇的一次局地暴雨天气的雷达回波特征,试图总结暴雨天气的雷达回波特点。结果表明,多普勒雷达回波强度出现大于35 dBz的回波,并有45～55 dBz的强回波持续出现在回波区域内,且回波稳定少动有一小时之多,这是产生暴雨的关键原因;径向速度产品出现逆风区,是暴雨天气速度回波的明显特征;垂直累积液态含水量产品和垂直风廓线产品对暴雨天气的分析有很好的辅助作用。     

Deuterium oxide: direct action on sympathetic ganglia isolated in culture

Immature ganglia from chicks and rodents were maintained as organized, developing cultures for 2 months or more, during which time they were continuously exposed to deuterium oxide in their medium. Observations of the living cell communities with the light microscope indicated that deuteration within viable limits (up to 25 percent) accelerates and increases the growth of sympathetic neurons and favors their repeated subdivision as a very large size is attained, thus inducing them to recapitulate cyclically the early stages of neurogenesis. Living deuterated cells appear more opaque and heteromerous than control neurons; furthermore, electron micrographs reveal an unusual abundance of granular and fibrillar elements in the nuclei of both neurons and supporting cells. Sheaves of complexly organized fibrillar components appear in the neuronal perikaryon; and ribosomes, Golgi elements, and microtubules are conspicuously numerous. Both fine structure and function of these ganglia therefore appear to have been modified directly by action of the deuterium isotope.     

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.     

Electrical signal measurement in plants using blind source separation with independent component analysis

Electrical signals of a plant leaf measured using surface recording are mixed signals which involve the electrical activities of the epidermis cells, guard cells, and mesophyll cells. Blind source separation (BSS) is a general signal processing approach, which estimates the source signals independently if the unknown signal sources are made by mixing linearly. The independent component analysis (ICA) method is one technique used to solve the blind source separation (BSS) problem. In contrast with conventional measuring methods used to investigate the electrical signals of plant cells with a complex treatment procedure, the ICA method was provided to achieve separation of the mixed electrical signals to recover the individual signals of each type of cells non-invasively. The proposed method has been tested using simulated signals and real plant electrical signal recordings. The results showed that ICA algorithms provided an efficient tool for the identification of the independent signal components from surface electrode recordings.     

胚胎发育合子型基因激活(ZGA)的调控机制

新受精卵超越早期分裂阶段必需胚胎基因转录 ( ZGA)的重新起动与续后调控 ,在各类动物早期卵裂过程的胚胎基因转录起动精确时间是可变的 ,涉及染色质结构成分、调控元件 (顺 /反式 )、RNA降解、DNA复制、修饰或加工作用、卵子发生因子、合子钟及天然信号等多种因素 ,因此提出哺乳动物胚胎发育期胚胎基因激活表达的调控机制     

Variations on conserved signaling pathways in biocontrol and development:G protein and MAPK genes of Trichoderma. atroviride and T. virens

Filamentous fungi employ conserved eukaryotic signaling pathway to detect and respond to environmental signals, including the presence of the host. Genetic experiment in which a particular signaling protein is lost, or its activity enhanced, have defined some of the function of heterotrimeric G proteins and MAP kinases in development and virulence. A hallmark of these studies is that orthologs in different species may have different functions. Antagonistic fungal-fungal interactions form …     

Temporal selectivity in the central auditory system of the leopard frog

Amplitude modulation is a predominant temporal feature in many vocal signals. The leopard frog, Rana pipiens, has a class of neurons in the central auditory system that respond selectively to particular rates of amplitude modulation; these neurons can be characterized by a temporal tuning curve. Such selectivity is absent in the peripheral auditory system. This type of transformation may be fundamental in processing temporal information in the vertebrate sensory nervous system.     

Radar glory from buried craters on icy moons

Three ice-covered moons of Jupiter, in comparison with rocky planets and Earth's moon, produce radar echoes of astounding strengths and bizarre polarizations. Scattering from buried craters can explain these and other anomalous properties of the echoes. The role of such craters is analogous to that of the water droplets that create the apparition known as "the glory," the optically bright region surrounding an observer's shadow on a cloud. Both situations involve the electromagnetic phenomenon of total internal reflection at a dielectric interface, operating in a geometry that strongly favors exact backscattering. Dim surface craters are transformed into bright glory holes by being buried under somewhat denser material, thereby increasing the intensity of their echoes by factors of hundreds. The dielectric interface thus formed at the crater walls nicely accounts for the unusual polarizations of the echoes.     

Rapid increase in clusters of presynaptic proteins at onset of long-lasting potentiation

A change in the efficiency of synaptic communication between neurons is thought to underlie learning. Consistent with recent studies of such changes, we find that long-lasting potentiation of synaptic transmission between cultured hippocampal neurons is accompanied by an increase in the number of clusters of postsynaptic glutamate receptors containing the subunit GluR1. In addition, potentiation is accompanied by a rapid and long-lasting increase in the number of clusters of the presynaptic protein synaptophysin and the number of sites at which synaptophysin and GluR1 are colocalized. These results suggest that potentiation involves rapid coordinate changes in the distribution of proteins in the presynaptic neuron as well as the postsynaptic neuron.     

Solar neutrinos: experimental approaches

This article discusses the new experiments, under way or proposed, that will measure the flux of solar neutrinos and so probe the "solar neutrino puzzle." Both radiochemical and electronic detector experiments are analyzed in terms of possible findings relevant to astrophysics and neutrino properties. Important elements are sensitivity to the principal components of the solar neutrino spectrum, directionality of the detector response, and an energy-measuring capability that might provide a unique identifying signal. Experiments beyond those currently under way will probably be needed, and development of real-time detectors is particularly important.     

拖拉机变速箱齿轮故障诊断智能软件的设计与实现

人们在采用人工神经网络进行智能信号处理时,需要较深入学习人工神经网络的理论。为解决这个问题,该研究设计了一种"傻瓜型"的神经网络智能信号处理软件,使用该软件,可以降低神经网络应用于智能信号处理的门槛,推进智能信号处理在拖拉机变速箱齿轮故障诊断方面的应用。     

一次局地暴雨天气的多普勒雷达回波分析

利用海拉尔新一代多普勒天气雷达资料,分析了2007年6月30日发生在陈巴尔虎旗的暴雨天气过程。得出结论:在大尺度环流背景条件对暴雨天气无明显指示的环境下,当地气象要素的高湿特征为暴雨发生提供了适宜的水汽条件;在暴雨发生过程中雷达回波稳定而少动,径向速度回波有清楚的逆风区,并且垂直累积液态含水量产品和垂直风廓线产品有明显的指示意义。     

Gigahertz electron spin manipulation using voltage-controlled g-tensor modulation

We present a scheme that enables gigahertz-bandwidth three-dimensional control of electron spins in a semiconductor heterostructure with the use of a single voltage signal. Microwave modulation of the Landé g tensor produces frequency-modulated electron spin precession. Driving at the Larmor frequency results in g-tensor modulation resonance, which is functionally equivalent to electron spin resonance but without the use of time-dependent magnetic fields. These results provide proof of the concept that quantum spin information can be locally manipulated with the use of high-speed electrical circuits.     

Covalent Group IV Atomic Clusters

Atomic clusters containing from two to several hundred atoms offer the possibility of studying the transition from molecules to crystalline solids. The covalent group IV elements carbon, silicon, and germanium are now being examined with this long-range objective. These elements are particularly interesting because of the very different character of their crystalline solids and because they are intermediate between metals and insulators in the nature of their bonding. Small mass-selected atom cluster ions are formed by pulsed laser techniques and identified by time-of-flight methods. Laser photoexcitation is used to study the relative stability of these clusters and their modes of fragmentation. These modes for C(n)(+) clusters, which tend to fragment with a characteristic loss of a neutral C(3), are found to be different from the modes for Si(n)(+) and Ge(n)(+) clusters, which tend to fragment to "magic" clusters such as Si(4)(+), Si(6)(+) and Si(10)(+). These experimental results can be accounted for by recent theoretical calculations of the ground-state structure and stability of small silicon and carbon clusters. Several theoretical approaches give consistent results, showing that small silicon clusters are compact and different from small fragments of the bulk crystal. Calculations show that carbon clusters change from linear structures toward cyclic structures as the cluster size increases, but with significant odd-even differences.