抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://www2.econ.iastate.edu/tesfatsi/DeepLearningInNeuralNetworksOverview.JSchmidhuber2015.pdf

Deep learning in neural networks

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

In cultures of dissociated rat hippocampal neurons, persistent potentiation and depression of glutamatergic synapses were induced by correlated spiking of presynaptic and postsynaptic neurons. The relative timing between the presynaptic and postsynaptic spiking determined the direction and the extent of synaptic changes. Repetitive postsynaptic spiking within a time window of 20 msec after presynaptic activation resulted in long-term potentiation (LTP), whereas postsynaptic spiking within a window of 20 msec before the repetitive presynaptic activation led to long-term depression (LTD). Significant LTP occurred only at synapses with relatively low initial strength, whereas the extent of LTD did not show obvious dependence on the initial synaptic strength. Both LTP and LTD depended on the activation of NMDA receptors and were absent in cases in which the postsynaptic neurons were GABAergic in nature. Blockade of L-type calcium channels with nimodipine abolished the induction of LTD and reduced the extent of LTP. These results underscore the importance of precise spike timing, synaptic strength, and postsynaptic cell type in the activity-induced modification of central synapses and suggest that Hebb’s rule may need to incorporate a quantitative consideration of spike timing that reflects the narrow and asymmetric window for the induction of synaptic modification.

https://www.jneurosci.org/content/jneuro/18/24/10464.full.pdf

Synaptic Modifications in Cultured Hippocampal Neurons: Dependence on Spike Timing, Synaptic Strength, and Postsynaptic Cell Type

N G van Kampen 1981 Amsterdam: North-Holland xiv + 419 pp price Dfl 180 This is a book which, at a lower price, could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes, as well as those who just enjoy a beautifully written book. It provides an extensive graduate-level introduction which is clear, cautious, interesting and readable.

https://iopscience.iop.org/article/10.1088/0031-9112/34/4/040/pdf

Stochastic Processes in Physics and Chemistry

How can an animal learn from experience? How can it train sensors, such as the auditory or tactile system, based on other sensory input such as the visual system? Supervised spike-timing-dependent plasticity supervised STDP is a possible answer Supervised STDP trains one modality using input from another one as "supervisor" Quite complex time-dependent relationships between the senses can be learned Here we prove that under very general conditions, supervised STDP converges to a stable configuration of synaptic weights leading to a reconstruction of primary sensory input

Supervised spike-timing-dependent plasticity: A spatiotemporal neuronal learning rule for function approximation and decisions

Animals that are small compared to sound wavelengths face the challenge of localizing a sound source since the main cues to sound direction—interaural time differences (ITD) and interaural level differences (ILD)—both depend on size. Remarkably, the majority of terrestrial vertebrates possess internally coupled ears (ICE) with an air-filled cavity connecting the two eardrums and producing an inherently directional middle-ear system. Underwater, longer wavelengths and faster sound-speed reduce both ITD and ILD cues. Nonetheless, many animals communicate through and localize underwater sound. Here, a typical representative equipped with ICE is studied: the fully aquatic clawed frog Xenopus laevis. It is shown that two factors improve underwater sound-localization quality. First, inflated lungs function as Helmholtz resonator and generate directional amplitude differences between eardrum vibrations in the high-frequency (1.7–2.2 kHz) and low-frequency (0.8–1.2 kHz) range of the male advertisement calls. Though the externally arriving ILDs practically vanish, the perceived internal level differences are appreciable, more than 10 dB. As opposed to, e.g., lizards with thin and flexible eardrums, plate-like eardrums are shown to be Xenopus' second key to successfully handling aquatic surroundings. Based on ICE, both plate-like eardrums and inflated lungs functioning as Helmholtz resonators explain the phonotaxis performance of Xenopus.Animals that are small compared to sound wavelengths face the challenge of localizing a sound source since the main cues to sound direction—interaural time differences (ITD) and interaural level differences (ILD)—both depend on size. Remarkably, the majority of terrestrial vertebrates possess internally coupled ears (ICE) with an air-filled cavity connecting the two eardrums and producing an inherently directional middle-ear system. Underwater, longer wavelengths and faster sound-speed reduce both ITD and ILD cues. Nonetheless, many animals communicate through and localize underwater sound. Here, a typical representative equipped with ICE is studied: the fully aquatic clawed frog Xenopus laevis. It is shown that two factors improve underwater sound-localization quality. First, inflated lungs function as Helmholtz resonator and generate directional amplitude differences between eardrum vibrations in the high-frequency (1.7–2.2 kHz) and low-frequency (0.8–1.2 kHz) range of the male advertisement calls. Thou...

https://findresearcher.sdu.dk:8443/ws/files/145912164/Modeling_underwater_hearing_and_sound_localization_in_the_frog_Xenopus_laevis.pdf

Modeling underwater hearing and sound localization in the frog Xenopus laevis

A model of vertical signal flow across a layered cortical structure is presented and analyzed. Neurons communicate through spikes, which evoke an excitatory or inhibitory postsynaptic potential (spike response model). The layers incorporate two anatomical features - dendritic and axonal arborization patterns and distance-dependent time delays. The vertical signal flow through the network is discussed for various stimulus conditions using two different, but typical, axonal arborization patterns. We find stationary as well as oscillatory response, but the oscillatory response may be restricted to a single layer. Confronted with conflicting stimuli the network separates the patterns through phase-shifted oscillations. We also discuss two hypothetical animals, to be called “cat” and “mouse.” These have different axonal arborizations, which give rise to a different oscillatory response (if any) of the various layers.

/pdf/vertical-signal-flow-and-oscillations-in-a-three-layer-model-4fv1mp1bl5.pdf

Vertical signal flow and oscillations in a three-layer model of the cortex.

is more than half a century ago since Donald Hebb published his classic book on the organization of behavior (Hebb 1949). Though highly readable, it has been cited in the computational/theoretical neuroscience literature much more often than it has been read. Why is this? On p. 62 of the book one finds the now-famous neurophysiological postulate: ''When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased''. This simple and self-explanatory hypothesis to explain synaptic ''learning'' also aroused considerable debate, because the mechanism was local. ''Locality'' is the appealing idea that a synaptic efficacy is determined by the information that is available to pre-and postsynaptic neurons both in space and in time – but nothing else. One then may wonder, of course, where the above ''metabolic change'' might take place. Hebb directly continued by suggesting that ''synaptic knobs develop'', and on p. 65 he states very explicitly: ''I have chosen to assume that the growth of synaptic knobs, with or without neurobiotaxis, is the basis of the change of facilitation from one cell on another, and this is not altogether implausible''. No, it is not. We even perceive the assertion as a commonplace, though in Hebb's time it was a breakthrough. Since its original formulation in English (but none other), the central question implied by Hebb's postulate has been how to implement it. Most of the information that is presented to a neuronal network varies in space and time, and thus requires a common representation of both the spatial and the temporal aspects of the input. As neuronal activity changes, the responding system should be able to measure and, if necessary, store this change. How can it do so? By now we know the Hebb rule works by means of a learning window in the context of spike-timing-dependent synaptic plasticity. Through the learning window a temporal mechanism ''looks'' at the arrival of a presynaptic spike in relation to the postsynaptic firing time. If a spike arrives at, for example, an excitatory synapse not too long before the postsynaptic neuron fires, the synapse strengthens; otherwise, if the spike is ''too late'', the connection is weakened. Locality in space was a hypothesis clearly formulated …

Hebb in perspective.

We revisit the method of conformal mapping and apply it to the setting found in mechanosensory detection systems such as the lateral-line system of fish. We derive easy-to-use equations capable of describing analytically the influence of the stimulus shape on the flow field and thus on the input to the lateral line. The present approach shows that the shape of a submerged moving object affects its perception if its distance to a detecting animal does not exceed the object’s body length.

J. Leo van Hemmen

Papers

Supervised spike-timing-dependent plasticity: A spatiotemporal neuronal learning rule for function approximation and decisions

Modeling underwater hearing and sound localization in the frog Xenopus laevis

Vertical signal flow and oscillations in a three-layer model of the cortex.

Hebb in perspective.

How stimulus shape affects lateral-line perception: analytical approach to analyze natural stimuli characteristics