Showing papers by "Max Planck Society published in 1982"

Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak

Abstract: A new operational regime has been observed in neutral-injection-heated ASDEX divertor discharges. This regime is characterized by high ${\ensuremath{\beta}}_{p}$ values comparable to the aspect ratio $A({\ensuremath{\beta}}_{p}l~0.65A)$ and by confinement times close to those of Ohmic discharges. The high-${\ensuremath{\beta}}_{p}$ regime develops at an injection power \ensuremath{\ge}1.9 MW, a mean density ${\overline{n}}_{e}g~3\ifmmode\times\else\texttimes\fi{}{10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, and a $q(a)$ value \ensuremath{\ge}2.6. Beyond these limits or in discharges with material limiter, low ${\ensuremath{\beta}}_{p}$ values and reduced particle and energy confinement times are obtained compared to the Ohmic heating phase.

Sodium and calcium channels in bovine chromaffin cells

Abstract: 1. Inward currents in chromaffin cells were studied with the patch-clamp technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981). The intracellular solution contained 120 mM-Cs+ and 20 mM-tetraethylammonium (TEA+). Na+ currents were studied after blockade of Ca2+ channels with 1 mM-Co2+ applied externally. Ca2+ currents were recorded after eliminating Na+ currents with tetrodotoxin (TTX). The current recordings were obtained in cell-attached, outside-out and whole-cell recording configurations (Hamill et al. 1981). 2. Single channel measurements gave an elementary current amplitude of 1 pA at -10 mV for Na+ channels. This amplitude increased with hyperpolarization between -10 and -40 mV, but did not vary significantly between -40 and -70 mV. 3. The mean Na+ channel open time was 1 ms at -30 mV. This open time decreased both with depolarization and hyperpolarization. Its value was close to the time constant of inactivation, τh, above -20 mV. 4. Ensemble fluctuation analysis of Na+ currents gave results consistent with those of single channel measurements. Noise power spectra obtained between -35 mV and 0 mV could be fitted with a single Lorentzian. A range of Na+ channel densities of 1·5-10 channels per μm2 was calculated. 5. Cell-attached single Ca2+ channel recordings were obtained in isotonic BaCl2 solution. The single channel amplitude was 0·9 pA at -5 mV, and it became smaller for positive potential values. 6. At -5 mV, single Ba2+ currents appeared as bursts of 1·9 ms mean duration containing on the average 0·6 short gaps. The burst duration was larger at positive potentials. 7. Ensemble fluctuation analysis of Ca2+ channels was performed on whole-cell recordings in external solutions containing isotonic BaCl2 or external Ca2+ (Cao) concentrations of 1 and 5 mM. The unit amplitude calculated in the former case was similar to that obtained in single channel measurements. 8. Noise power spectra of Ca2+ or Ba2+ currents could be fitted by the sum of two, but not one, Lorentzian components. 9. Tail currents could be fitted by the sum of two exponential components. The corresponding time constants had values close to those obtained with noise analysis. 10. The rising phase of Ca2+ and Ba2+ currents was sigmoid. It could be fitted by the sum of three exponentials. The time constant of the largest amplitude component, τ1, was similar to the time constants of the slow component observed in noise and tail experiments. This time constant also corresponded to the burst duration obtained in single channel measurements. 11. The value of τ1 was larger in 5 mM-Cao and in isotonic Ba2+ than in 5 mM-Bao. Thus, the kinetic properties of Ca2+ channels depend on the nature and concentration of the permeating ion. 12. A simple kinetic scheme is proposed to model the activation pathway of Ca2+ channels. 13. Currents in 1 mM-Cao and 5 mM-Cao showed clear reversals around +53 mV and +64 mV respectively. The outward currents observed above these potentials are most probably due to Cs+ ions flowing through Ca2+ channels. 14. The instantaneous current—voltage relation was obtained from tail current data in the range -70 to +100 mV in 5 mM-Cao. The resulting curve displayed an inflexion point around the reversal potential. 15. Very little inactivation of Ca2+ currents was observed. However, a slow current decline was observed in some cells above +10 mV. 16. Conditioning prepulses to positive potentials had potentiating or depressing effects on Ca2+ currents depending on whether the test pulse lay below or above the maximal current potential. The potentiating effect may be linked to the slowest component of the current rise observed below +10 mV. The depressing effect may be related to the slow decline obtained above +10 mV. 17. Analysis of ensemble variance and of tail current amplitudes suggested that the opening probability of Ca2+ channels was at least 0·9 above +40 mV. 18. A slow rundown of Ca2+ currents was observed in whole-cell recordings. The speed of the rundown was dependent on intracellular Ca2+ concentration. The rundown was apparently due to a progressive elimination of the channels available for activation. 19. The density of Ca2+ channels (before rundown) was estimated at 5-15/μm2. 20. In cell-attached experiments, inward current channels were often seen to follow action potentials. These events did not appear to be the usual Na+ and Ca2+ currents. They were probably due to cation influx of either Na+ or Ba2+, depending on the pipette solution, through Ca2+-dependent channels. Voltage-independent single channel activity observed in whole-cell and outside-out recordings may be due to the same channels.

Solar wind protons: Three-dimensional velocity distributions and derived plasma parameters measured between 0.3 and 1 AU

Abstract: Such nonthermal features as temperature anisotropies, heat fluxes, and proton double streams have been observed by a Helios solar probe survey of solar wind three-dimensional proton velocity distributions between 0.3 and 1 AU. It is found that a strong anisotropy in the core of proton distributions, with a temperature that is larger perpendicular rather than parallel to the magnetic field, is a persistent feature of high-speed streams, becoming most pronounced in the perihelion, or about 0.3 AU. Isotropic distributions have been detected only close to, and at, magnetic sector boundaries, and the flattest radial temperature profiles are found in high-speed streams. These observations indicate that local heating or proton heat conduction occurs in the solar wind.

Sr and Nd isotope geochemistry of oceanic basalts and mantle evolution

Abstract: Sr and Nd isotope ratios are reported for 17 mid-ocean ridge basalts and for 11 oceanic islands and island groups. Data from the Azores, Samoa and the Society Islands diverge significantly from the mantle array. These results are not explained by binary mixing of depleted and undepleted mantle reservoirs or by variable magmatic depletion of a planetary reservoir, but support mantle evolution models involving re-injection of crust material into the mantle.

Primary structure of the human Met- and Leu-enkephalin precursor and its mRNA

Abstract: The nucleotide sequence of a complete cDNA copy of enkephalin precursor mRNA from human phaeochromocytoma is reported The corresponding amino acid sequence shows that the precursor is 267 amino acids long and contains six interspersed Met-enkephalin sequences and one Leu-enkephalin sequence Five of the seven enkephalins are flanked on both sides by pairs of basic amino acid residues The precursors does not contain the sequences of the opioid peptides, dynorphin, alpha-neo-endorphin or beta-endorphin

Quantum eraser: A proposed photon correlation experiment concerning observation and "delayed choice" in quantum mechanics

Abstract: We propose and analyze an experiment designed to probe the extent to which information accessible to an observer and the "eraser" of this information affects measured results. The proposed experiment could also be operated in a "delayed-choice" mode.

Molecular cloning establishes proenkephalin as precursor of enkephalin-containing peptides

Abstract: Molecular cloning and DNA sequencing have yielded considerable structural information about proenkephalin. All previously characterized intermediate peptides of the enkephalin pathway in bovine adrenal medulla have now been aligned into an unambiguous primary structure. Two basic amino acid residues serve as processing signals for release of each of the different components.

Plasma–wall transition in an oblique magnetic field

Abstract: The effect of a magnetic field on the transition layer between a plasma and an absorbing wall is studied. A numerical model is used which simulates the motion of plasma particles in the electric and magnetic fields for a prescribed particle influx at the plasma boundary. Bohm’s condition for the existence of a monotonic profile of the layer is generalized. The transition layer proves to have a double structure comprising a quasineutral magnetic presheath preceding the electrostatic Debye sheath. The magnetic presheath scales with the ion gyroradius at the sound speed and with the angle of the magnetic field. The total electric potential drop between plasma and wall proves to be fairly insensitive to the magnitude and angle of the magnetic field.

Stability of Tetragonal ZrO2 Particles in Ceramic Matrices

Abstract: The stability of tetragonal ZrO2 particles in ceramic matrices was considered, with particular reference to Al2O3-ZrO2 composites and to partially stabilized ZrO2. In both systems, particles above a “critical” size transform martensitically to monoclinic symmetry on cooling to room temperature. The critical factors that could affect the size dependence of the transformation temperature—surface and strain energy effects, the chemical free energy driving force, and the difficulty of nucleating the martensitic transformation—were considered. Nucleation arguments are probably the most important.

Retinal Ganglion Cells: A Functional Interpretation of Dendritic Morphology

Abstract: The electrical properties of the different anatomical types of retinal ganglion cells in the cat were calculated on the basis of passive cable theory from measurements made on histological material. Standard values for the electrical parameters were assumed (R $\_i$ = 70 $\Omega$ cm, C $\_m$ = 2 $\mu$ F cm $^{-2}$ , R $\_m$ = 2500 $\Omega$ cm $^2$ ). We conclude that these neurons need not be equipotential despite their small dimensions, mainly because of their extensive branching. The interactions between excitation and inhibition when the inhibitory battery is near the resting potential can be strongly nonlinear in these cells. To characterize the different types of ganglion cells in terms of this property we introduce F, the factor by which the soma depolarization induced by a given excitatory input is reduced by inhibition. In this framework we analyse some of the integrative properties of an arbitrary passive dendritic tree and we then derive the functional properties that are characteristic for the various types of ganglion cells. Our main results are: (i) Nonlinear saturation at the synapses may be made effectively smaller by spreading the same (conductance) input among several subunits on the dendritic field. Subunits are defined as regions of the dendritic field that are somewhat isolated from each other and roughly equipotential within. (ii) Shunting inhibition can specifically veto an excitatory input, if it is located on the direct path to the soma. The F values can then be very high even when the excitatory inputs are much larger than the inhibitory, as long as the absolute value of inhibition is not too small. Inhibition more distal than excitation is much less effective. (iii) Specific branching patterns coupled with suitable distribution of synapses are potentially able to support complex information processing operations on the incoming excitatory and inhibitory signals. The quantitative analysis of the morphology of cat retinal ganglion cells leads to the following specific conclusions: (i) None of the cells examined satisfies Rall's equivalent cylinder condition. The dendritic tree cannot be satisfactorily approximated by a non-tapering cylinder. (ii) Under the assumption of a passive membrane, the dendritic architecture of the different types of retinal ganglion cells reflects characteristically different electrical properties, which are likely to be relevant for their physiological function and their information processing role: (a) $\alpha$ cells have spatially inhomogeneous electrical properties, with many subunits. Within each subunit nonlinear effects may take place; between subunits good linear summation is expected. F values are relatively low. (b) $\beta$ cells at small eccentricities have rather homogeneous electrical properties. Even distal inputs are weighted rather uniformly. Electrical inhomogeneities of the $\alpha$ type appear for $\beta$ cells at larger eccentricities. F values are low. (c) $\gamma$ -like cells have few subunits, each with high input resistance underlying nonlinear saturation effects possibly related to a sluggish character. F values are high: inhibition of the shunting type can interact in a strongly nonlinear way with excitatory conductance inputs. (d) $\delta$ -like cells show many subunits with a high input resistance, covering well the dendritic area. Within each subunit inhibition on the direct path to the soma can specifically veto a more distal excitation. It is conjectured that such a synaptic organization superimposed on the $\delta$ cell morphology underlies directional selectivity to motion. (iii) Most of our data refer to steady-state properties. They probably apply, however, to all light evoked signals, since transient inputs with time to peak of 30 ms or more can be treated in terms of steady-state properties of the ganglion cells studied. (iv) All our results are affected only slightly by varying the parameter values within reasonable ranges. If, however, the membrane resistance were very high, all ganglion cells would approach equipotentiality. For R $\_m$ = 8000 $\Omega$ cm $^2$ subunits essentially disappear in all types of ganglion cells (for steady state inputs). Our results concerning nonlinear interaction of excitation and inhibition (F values) would, however, remain valid even for much larger values of R $\_m$ and for any value of R $\_i$ larger than 30-50 $\Omega$ cm. The critical requirement is that peak inhibitory conductance changes must be sufficiently large (around 5 x 10 $^{-8}$ S) with an equilibrium potential close to the resting potential. Underestimation of the diameters of the dendritic branches may affect these conclusions (F could be significantly lower).

Solar wind helium ions - Observations of the Helios solar probes between 0.3 and 1 AU

Abstract: A Helios solar probe survey of solar wind helium ion velocity distributions and derived parameters between 0.3 and 1 AU is presented. Distributions in high-speed wind are found to generally have small total anisotropies, with some indication that, in the core part, the temperatures are greater parallel rather than perpendicular to the magnetic field. The anisotropy tends to increase with heliocentric radial distance, and the average dependence of helium ion temperatures on radial distance from the sun is described by a power law. Differential ion speeds with values of more than 150 km/sec are observed near perihelion, or 0.3 AU. The role of Coulomb collisions in limiting differential ion speeds and the ion temperature ratio is investigated, and it is found that collisions play a distinct role in low-speed wind, by limiting both differential ion velocity and temperature.

Differential expression of neurofilament triplet proteins in brain development.

Abstract: Axonal transport studies and biochemical fractionation have led to the concept that the three 'triplet' proteins [approximate molecular weights 200,000 (200K), 145,000 (145K) and 68,000 (68K)] are the essential components of mammalian neurofilaments. Using a correlated biochemical and immunological approach, we have now shown that the 200K protein is under separate developmental control during rat brain differentiation and that the time of its expression differs in different regions. We were unable to detect 200K protein by immunofluorescence or in total brain filament preparations from prenatal rat brain, although the 145K and 68K proteins are both present in an apparently identical distribution. During development, progressively more 145K- and 68K-positive neurofilamentous bundles can be stained with 200K antibodies, paralleling the increasing quantities of this protein detected biochemically in brain filament preparations. We conclude that 200K protein probably has a more specialized role in neurofilament architecture and function than the other two triplet proteins.

One-electron redox potentials of phenols. Hydroxy- and aminophenols and related compounds of biological interest

Abstract: The rate constants for reversible electron transfer between a series of substituted phenolate ions and anilines and various substituted phenoxyl or anilino radicals in aqueous solution were measured by observing the formation or depletion of the radicals involved. Nonequilibrium concentrations of the radicals were produced in the presence of the corresponding phenols or anilines by using the pulse radiolysis technique. The relaxation of the system to equilibrium was monitored by optical detection methods. From the equilibrium constants for one-electron transfer, the one-electron redox potentials (E/sup 2/) for 38 phenolic or anilino type compounds were determined, many of which are natural products. The redox potentials are strongly influenced by electron-donating or -withdrawing substituents at the aromatic system. 3 figures, 5 tables.

Immunofluorescence and immunocytochemical procedures with affinity purified antibodies: tubulin-containing structures.

Abstract: Publisher Summary This chapter describes the study of the intracellular location of proteins by immunocytochemical procedures. Although the methods given in the chapter are generally applicable, they are documented for tubulin containing structures and antibodies to tubulin. Further examples of the usefulness of these methods in studying cell structure can be found in several recent reviews. Immunofluorescence microscopy is a very sensitive method, theoretically requiring only one antigenic site on the structural protein. It offers several unique advantages for the study of cytoskeletal structures. First, only the protein of choice is visualized by use of its specific antibody. Second, if the protein forms part of a supramolecular structure, the organization of that structure throughout the cell can be demonstrated. Third, numerous cells can be observed simultaneously, and thus the unique features of the organization under different experimental conditions can be observed. Thus, immunofluorescence microscopy can bridge the gap between light microscopy and electron microscopy.

Plasma and magnetic field characteristics of magnetic flux transfer events

Abstract: Plasma and magnetic field data from ISEE 1 and 2 are examined for 5 passes of the magnetopause region at 20 and 40 deg northern latitudes, and are presented in terms of moments of the distribution function, calculated from two-dimensional or three-dimensional data. Flux transfer events are characterized by a mixture of magnetosheath and magnetospheric particles, which supports the hypothesis that flux transfer events represent encounters of reconnected flux tubes. An excess pressure appears to be balanced by the tension of the ambient magnetic field lines as they are draped around the reconnected flux tube, and the different observed magnetic field signatures are consistent with expectations for encounters of the flux tubes at different relative locations. It is suggested that increased flow speeds are caused by continued reconnection at the low-latitude boundaries of the flux tubes.

Motion sensitive interneurons in the optomotor system of the fly

Abstract: The functional properties of the three horizontal cells (north horizontal cell, HSN; equatorial horizontal cell, HSE; south horizontal cell, HSS) in the lobula plate of the blowflyCalliphora erythrocephala were investigated electrophysiologically. 1. The receptive fields of the HSN, HSE, and HSS cover the dorsal, equatorial and ventral part of the ipsilateral visual field, respectively. In all three cells, the sensitivity to visual stimulation is highest in the frontal visual field and decreases laterally. The receptive fields and spatial sensitivity distributions of the horizontal cells are directly determined by the position and extension of their dendritic fields in the lobula plate and the dendritic density distributions within these fields. 2. The horizontal cells respond mainly to progressive (front to back) motion and are inhibited by motion in the reverse direction, the preferred and null direction being antiparallel. The amplitudes of motion induced excitatory and inhibitory responses decline like a cosine function with increasing deviation of the direction of motion from the preferred direction. Stimulation with motion in directions perpendicular to the preferred direction is ineffective. 3. The preferred directions of the horizontal cells show characteristic gradual orientation changes in different parts of the receptive fields: they are horizontally oriented only in the equatorial region and increasingly tilted vertically towards the dorsofrontal and ventrofrontal margins of the visual field. These orientation changes can be correlated with equivalent changes in the local orientation of the lattice of ommatidial axes in the pertinent compound eye. 4. The response amplitudes of the horizontal cells under stimulation with a moving periodic grating depend strongly on the contrast frequency of the stimulus. Maximal responses were found at contrast frequencies of 2---5 Hz. 5. The spatial integration properties of the horizontal cells (studied in the HSE) are highly nonlinear. Under stimulation with extended moving patterns, their response amplitudes are nearly independent of the size of the stimuli. It is demonstrated that this response behaviour does not result from postsynaptic saturation in the dendrites of the cells. The results indicate that the horizontal system is essentially involved in the neural control of optomotor torque responses performed by the fly in order to minimize unvoluntary deviations from a straight flight course.

Antibodies against a preselected peptide recognize and neutralize foot and mouth disease virus.

Abstract: A major antibody combining site on foot and mouth disease virus (FMDV) serotype O1K has been identified in a predicted surface helix of viral protein 1 (VP1) between amino acid residues 144 and 159. A hexadecapeptide covering this sequence elicits high titers of antibodies that specifically recognize and neutralize FMDV. The high quality of the immune response is attributed to a particularly stable conformation of the antigenic amino acid sequence, which is most likely an alpha-helix.

Flow-field variables trigger landing in flies

Abstract: The eyes of moving animals experience a continuously changing flow of stimulation. Information contained in this ‘optical flow field’ can be extracted to control movement1–4. I present here evidence that pre-landing deceleration in flies is determined by such information: onset of deceleration is triggered when the ratio of the image expansion of a target on the retina to the image size (‘relative retinal expansion velocity’, RREV) reaches a critical value.

The primary structure and genetic organization of the bovine papillomavirus type 1 genome.

Abstract: The complete nucleotide sequence of the double-stranded circular DNA of bovine papillomavirus type 1 (BPV-1) was determined. Analysis of this sequence in conjunction with known transcriptional data for the virus provides a basis for determining the organization of the papillomavirus genome. All the major open reading frames are located on the same DNA strand. The region transcribed in BPV-transformed cells contains open frames in all three translational frames whereas the region transcribed in productively infected bovine fibropapillomas is characterized by two large open reading frames partitioned by a single translational stop codon. The localization of sequences diagnostic of promoters and polyadenylation sites suggests that splicing is involved in the biosynthesis of the viral mRNAs. A sequence comparison indicates the genomic organization of the bovine papillomavirus and that of the members of the simian virus 40-polyomavirus subgroup to be distinct, suggesting that these two groups of viruses are evolutionarily unrelated.

The Human Growth Hormone Gene Family: Nucleotide Sequences Show Recent Divergence and Predict a New Polypeptide Hormone

Abstract: The nucleotide sequences of three nonallelic human genomic DNA fragments which each contain one member of the growth hormone gene family are presented. These genes code for the known polypeptide hormones, growth hormone (hGH), chorionic somatomammotropin (hCS), and a yet unknown protein which differs from hGH in 13 positions. Each gene is structured into five exons, the four introns occurring at identical positions. Reflecting recent gene divergence, 90-95% sequence homology is seen in exons, introns, 5′, and immediate 3′ nontranscribed regions. The regions downstream of the polyadenylation sites in the genes for hGH and its variant, but not for hCS, contain members of an Alu family repeat sequence.

Neural Assemblies: An Alternative Approach to Artificial Intelligence

Abstract: Contents, with Outline.- I.- 1 The Flow of Information.- An introduction to the brain with emphasis on the transmission of information. Digressions 1 and 2 start from here..- 2 Thinking as Seen from Within and from Without.- Some problems in thinking about thinking are presented the behavioristic approach to such problems is introduced: What in the observable behavior of somebody else makes us think that he is thinking? This leads to the Turing test for artificial intelligence..- 3 How to Build Well-Behaving Machines.- "Behavior" is understood as the total stimulus (or situation) ? response mapping. For a finite number of different inputs, any such mapping can be constructed. This statement is demonstrated by.- 1. coding of any finite set into finite 0, 1-sequences.- 2. showing that any mapping between finite sets of 0.1-sequences can be built from logical and-, or-, and not-gates..- 3. representing the and-, or-, and not-gate as special threshold neurons of the McCulloch and Pitts type..- Digression 3 may be of some help here..- 4 Organizations, Algorithms, and Flow Diagrams.- The chapter contains some general remarks on organizations and cooperativity and introduces the matchbox algorithm..- 5 The Improved Matchbox Algorithm.- The matchbox algorithm is improved by the incorporation of the look-ahead algorithm (e.g., for chess-playing machines) and the associative matrix memory. Appendix 1 starts from here. Chapters 5 and 7 contain the basic constructions needed for the survival algorithm..- 6 The Survival Algorithm as a Model of an Animal.- The improved matchbox algorithm is interpreted as an algorithm for survival and thus as a model of an animal If such an algorithm is implemented in terms of neuron-like elements, the result can be checked against experimental data from the neurosciences. Conversely, such data cannot really be understood without a theory (in line with a more general argument as for example in Kuhn 1962)..- 7 Specifying the Survival Algorithm.- Some further specifications of the survival algorithm are given that are necessary in order to implement the algorithm in terms of neurons. A neural realization of the survival algorithm is finally discussed in connection with some basic data on the brain (from Chap. 1) and in order to stimulate interest in further data as supplied in the following chapters. Digression 4 may be entered from here..- II.- 8 The Anatomy of the Cortical Connectivity.- Further data on the connectivity between neurons in the cerebral cortex are presented, leading to some speculations on the flow of neural activity in the cortex..- 9 The Visual Input to the Cortex.- The projection from the retina onto the visual cortex is outlined, to exemplify how sensory input information enters the cortex..- 10 Changes in the Cortex with Learning.- Various experiments correlate differences in the cortex with differences in the environments which had been experienced by experimental animals, and possibly with "learning". Some of these experiments are discussed with the object of obtaining evidence for Hebb'Contents, with Outline.- I.- 1 The Flow of Information.- An introduction to the brain with emphasis on the transmission of information. Digressions 1 and 2 start from here..- 2 Thinking as Seen from Within and from Without.- Some problems in thinking about thinking are presented the behavioristic approach to such problems is introduced: What in the observable behavior of somebody else makes us think that he is thinking? This leads to the Turing test for artificial intelligence..- 3 How to Build Well-Behaving Machines.- "Behavior" is understood as the total stimulus (or situation) ? response mapping. For a finite number of different inputs, any such mapping can be constructed. This statement is demonstrated by.- 1. coding of any finite set into finite 0, 1-sequences.- 2. showing that any mapping between finite sets of 0.1-sequences can be built from logical and-, or-, and not-gates..- 3. representing the and-, or-, and not-gate as special threshold neurons of the McCulloch and Pitts type..- Digression 3 may be of some help here..- 4 Organizations, Algorithms, and Flow Diagrams.- The chapter contains some general remarks on organizations and cooperativity and introduces the matchbox algorithm..- 5 The Improved Matchbox Algorithm.- The matchbox algorithm is improved by the incorporation of the look-ahead algorithm (e.g., for chess-playing machines) and the associative matrix memory. Appendix 1 starts from here. Chapters 5 and 7 contain the basic constructions needed for the survival algorithm..- 6 The Survival Algorithm as a Model of an Animal.- The improved matchbox algorithm is interpreted as an algorithm for survival and thus as a model of an animal If such an algorithm is implemented in terms of neuron-like elements, the result can be checked against experimental data from the neurosciences. Conversely, such data cannot really be understood without a theory (in line with a more general argument as for example in Kuhn 1962)..- 7 Specifying the Survival Algorithm.- Some further specifications of the survival algorithm are given that are necessary in order to implement the algorithm in terms of neurons. A neural realization of the survival algorithm is finally discussed in connection with some basic data on the brain (from Chap. 1) and in order to stimulate interest in further data as supplied in the following chapters. Digression 4 may be entered from here..- II.- 8 The Anatomy of the Cortical Connectivity.- Further data on the connectivity between neurons in the cerebral cortex are presented, leading to some speculations on the flow of neural activity in the cortex..- 9 The Visual Input to the Cortex.- The projection from the retina onto the visual cortex is outlined, to exemplify how sensory input information enters the cortex..- 10 Changes in the Cortex with Learning.- Various experiments correlate differences in the cortex with differences in the environments which had been experienced by experimental animals, and possibly with "learning". Some of these experiments are discussed with the object of obtaining evidence for Hebb's synaptic rule. Digression 4 may be consulted here..- 11 From Neural Dynamics to Cell Assemblies.- Several papers on neural dynamics are discussed in order.- 1. to obtain a more detailed image of the flow of activity in the neural network of the brain (or the cortex).- 2. to get a better understanding of the learning- and information processing capabilities of such networks (especially in comparison with the requirements of the survival algorithm of Chaps. 6 and 7)..- The resulting image is fixed in the language of cell assemblies. Appendix 2 and Digression 4 start from here..- 12 Introspection and the Rules of Threshold Control.- The same language of cell assemblies is used to describe some introspections of the author in a more systematic way. This leads to a few strategies for controlling the thresholds of the neurons in a neural network that is used as an associative memory (for example by a survival robot). Appendices 3 and 4 and Digression 5 start from here..- 13 Further Speculations.- The ideas of cell assemblies and threshold control are carried out further and in a more speculative way. Digression 6 starts from here. Chapters 12 and 13 (together with Digression 5) contain a speculative, algorithmic picture of the information processing in an animal's brain..- 14 Men, Monkeys, and Machines.- It is argued that this picture carries over to humans as well. The acquisition of language, in particular, is regarded as a phenomenon of cultural evolution..- 15 Why all These Speculations?.- The whole book can be understood as an attempt to reduce human behavior to electrophysiological events in the brain and finally to physics, which, of course, does not preclude a heuristic use of teleological arguments (the final purpose being survival and proliferation). Some ethical and epistemological consequences of this attempt are briefly discussed..- References.- Digressions.- 1 Electrical Signal Transmission in a Single Neuron.- 2 Basic Information Theory.- 3 Sets and Mappings.- 4 Local Synaptic Rules.- 5 Flow Diagram for a Survival Algorithm.- 6 Suggestions for Further Reading.- Appendices.- 1 On the Storage Capacity of Associative Memories.- 2 Neural Modeling.- 3 Cell Assemblies: the Basic Ideas.- 4 Cell Assemblies and Graph Theory.- Author and Subject Index.