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

This paper reviews some central notions of the theoretical biophysics of neural networks, viz., information coding through coherent firing of the neurons and spatio-temporal spike patterns. After an introduction to the neural coding problem we first turn to oscillator models and analyze their dynamics in terms of a Lyapunov function. The rest of the paper is devoted to spiking neurons, a pulse code. We review the current neuron models, introduce a new and more flexible one, the spike response model (SRM), and verify that it offers a realistic description of neuronal behavior. The corresponding spike statistics is considered as well. For a network of SRM neurons we present an analytic solution of its dynamics, analyze the possible asymptotic states, and check their stability. Special attention is given to coherent oscillations. Finally we show that Hebbian learning also works for low activity spatio-temporal spike patterns. The models which we study always describe globally connected networks and, thus, have a high degree of feedback. We only touch upon functional feedback, that is, feedback between areas that have different tasks. Information processing in conjunction with functional feedback is treated explicitly in a companion paper [94].

Coding and information processing in neural networks

The population vector code relates directional tuning of single cells and global, directional motion incited by an assembly of neurons. In this paper three things are done. First, we analyze the population vector code as a purely geometric construct, focusing attention on its universality. Second, we generalize the algorithm on the basis of its geometrical realization so that the same construct that responds to sensation can function as an actuator for behavioral output. Third, we suggest at least a partial answer to the question of what many maps, neuronal representations of the outside sensory world in space–time, are good for: encoding vectorial input they enable a direct realization of the population vector code.

http://www.t35.physik.tu-muenchen.de/addons/publications/van_Hemmen-2008.pdf

Population vector code: a geometric universal as actuator

Lizards and many birds possess a specialized hearing mechanism: internally coupled ears where the tympanic membranes connect through a large mouth cavity so that the vibrations of the tympanic membranes influence each other. This coupling enhances the phase differences and creates amplitude differences in the tympanic membrane vibrations. Both cues show strong directionality. The work presented herein sets out the derivation of a three dimensional analytical model of internally coupled ears that allows for calculation of a complete vibration profile of the membranes. The analytical model additionally provides the opportunity to incorporate the effect of the asymmetrically attached columella, which leads to the activation of higher membrane vibration modes. Incorporating this effect, the analytical model can explain measurements taken from the tympanic membrane of a living lizard, for example, data demonstrating an asymmetrical spatial pattern of membrane vibration. As the analytical calculations show, the internally coupled ears increase the directional response, appearing in large directional internal amplitude differences (iAD) and in large internal time differences (iTD). Numerical simulations of the eigenfunctions in an exemplary, realistically reconstructed mouth cavity further estimate the effects of its complex geometry.

Analytical model of internally coupled ears.

The lateral-line system is a unique mechanosensory facility of aquatic animals that enables them not only to localize prey, predator, obstacles, and conspecifics, but also to recognize hydrodynamic objects. Here we present an explicit model explaining how aquatic animals such as fish can distinguish differently shaped submerged moving objects. Our model is based on the hydrodynamic multipole expansion and uses the unambiguous set of multipole components to identify the corresponding object. Furthermore, we show that within the natural range of one fish length the velocity field contains far more information than that due to a dipole. Finally, the model we present is easy to implement both neuronally and technically, and agrees well with available neuronal, physiological, and behavioral data on the lateral-line system.

http://www.t35.physik.tu-muenchen.de/addons/publications/Sichert-2009.pdf

Hydrodynamic object recognition: when multipoles count.

The Zwicker tone is an auditory aftereffect. For instance, after switching off a broadband noise with a spectral gap, one perceives it as a lingering pure tone with the pitch in the gap. It is a unique illusion in that it cannot be explained by known properties of the auditory periphery alone. Here we introduce a neuronal model explaining the Zwicker tone. We show that a neuronal noise-reduction mechanism in conjunction with dominantly unilateral inhibition explains the effect. A pure tone’s ‘‘hole burning’’ in noisy surroundings is given as an illustration. Zwicker [1] discovered an intriguing auditory aftereffect in 1964, now called the Zwicker tone. The typical sound generating it is a broadband noise containing a spectral gap, which is presented for several seconds. After the noise has been switched off, a faint, almost pure, tone is audible for 1 up to 6 s. It is decaying and has a sharp pitch in the spectral gap [1,2], where no stimulus was available. Both the localization of the Zwicker tone in the brain and its origin are long-standing open problems. Here we present a neuronal model explaining both. Through computer simulations based on our model of first processing stages of the auditory pathway following the cochlea, we show that both noise reduction and dominantly unilateral, in short, asymmetric inhibition along the tonotopic (frequency) axis are inherent properties of parts of the auditory system so as to allow the Zwicker tone to arise. We also explain why quite a few noise configurations (Fig. 1) do or do not generate a Zwicker tone [2,3,6,7]. Furthermore, we have successfully tested the model in psychoacoustic experiments described in [5]. All cases of Fig. 1 are explained by the model, as has been verified through extensive simulations. The Zwicker tone, as an almost pure tone, has a totally different quality from its generating noise. In Zwicker’s experimental setup [1] of Fig. 1(b), the tone was disjoint from the spectral range of the noise generating it. That is why Zwicker called it a ‘‘negative’’ afterimage. We now show that this aftereffect is double negative in that it is due to both noise reduction and asymmetric inhibition— and not to habituation, as in the visual system. Surprisingly, the Zwicker tone is inherently asymmetric. In the presence of broadband noise with a spectral gap, it exists above the lower band edge but not below the upper band edge of the gap; cf. Fig. 1(b). Neither does it exist at the high-pass edge in Fig. 1(f). The Zwicker tone has been found neither in the cochlea nor in the auditory nerve and cannot be explained by known properties of the auditory periphery either. Hence it is thought to have its origin in the central auditory system but it is not clear yet where precisely. It has been demonstrated to some extent in a primary auditory cortex both physiologically [8] and through magnetoencephalographic methods [9]. To explain the Zwicker tone by means of a neuronal model of the early auditory system, we start with a few facts, which are widely assumed to be basic. First, neurons are tonotopically ordered along a frequency axis

http://www.t35.physik.tu-muenchen.de/addons/publications/Franosch-2003.pdf

J. Leo van Hemmen

Papers

Coding and information processing in neural networks

Population vector code: a geometric universal as actuator

Analytical model of internally coupled ears.

Hydrodynamic object recognition: when multipoles count.

Zwicker tone illusion and noise reduction in the auditory system.