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PubMed1980

[The information content of intracellular water and its accumulation in embryo- and phylogenesis (author's transl)].

The nucleo-free erythrocytes is presented as the simplest differentiated cell whose energy-exchange has the single purpose of preserving the cell structure; this structure is based on the regular quasi-crystalline state of intracellular water, which is expressed by the negative entropy (-SW) and the temperature TW which is higher than the temperature of the extracellular water T. The information content of intracellular water, JW is proportional to the temperature difference: JW approximately delta T = TW - T. The regular state of intracellular water is maintained by the basal metabolism that takes place in the membrane of the differentiated cell. The energy exchange, i.e., the absorption of free energy and the liberation of an equivalent amount of heat, occurs in the form of work cycles of the enzyme-water-complexes in the cell membrane. The differentiated cell of the multicellular animal organism is the result of embryogenetic processes accompanied by heat-liberation. The specific heat-liberation, i.e., the heat produced by a single cell, begins with a quasi-zero value of the fertilized egg cell and grows with acceleration to a maximum value at the end of embryogenesis. This process of acceleration of heat-liberation is caused by the entrance of the water from the outer medium into the embryonic cell; the water undergoes the phase-change "fluid yields crystal" with heat-liberation. The intracellular water within the embryonic cell becomes structurated; this is also accompanied by growing heat-liberation. The thermodynamic characteristic of embryo genetic development is expressed by the principle of the maximum of velocity of entropy production of the cell at the end state of the process of differentiation. This principle applied to phylogenetics, leads to the formulation of the principle of accumulation of biological information: J(t). In the course of evolution living systems are able not only to store information of past generations, but also to create information: J(t) approximately e-1nt1!, where t is the time of phylogenesis.

Animals↗
PubMed1984

The structure of images.

In practice the relevant details of images exist only over a restricted range of scale. Hence it is important to study the dependence of image structure on the level of resolution. It seems clear enough that visual perception treats images on several levels of resolution simultaneously and that this fact must be important for the study of perception. However, no applicable mathematically formulated theory to deal with such problems appears to exist. In this paper it is shown that any image can be embedded in a one-parameter family of derived images (with resolution as the parameter) in essentially only one unique way if the constraint that no spurious detail should be generated when the resolution is diminished, is applied. The structure of this family is governed by the well known diffusion equation (a parabolic, linear, partial differential equation of the second order). As such the structure fits into existing theories that treat the front end of the visual system as a continuous stack of homogeneous layers, characterized by iterated local processing schemes. When resolution is decreased the images becomes less articulated because the extrem ("light and dark blobs") disappear one after the other. This erosion of structure is a simple process that is similar in every case. As a result any image can be described as a juxtaposed and nested set of light and dark blobs, wherein each blob has a limited range of resolution in which it manifests itself. The structure of the family of derived images permits a derivation of the sampling density required to sample the image at multiple scales of resolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Cybernetics↗
PubMed1980

Identification of figural elements in a visual domain.

Identification of figural elements is based upon comparison of one of several formal pattern descriptions with subjective similarity judgements. The best description appears to contain figural elements which are heavily dependent on the visual domain chosen for the experiment. Generally those figural elements seem to be involved which distinguish optimally between the reference patterns used to mark off the visual domain. An algorithm is proposed for searching figural elements which are building stones of optimal descriptions. The present study indicates that grammars generating structures based upon features, higher order figures and rules of composition may be tools for visual research.

Cybernetics↗
PubMed1985

A model for direction selectivity in threshold motion perception.

Thresholds were measured for a moving line superimposed on moving sinusoidal gratings. When line and grating moved in the same direction significant subthreshold summation was observed over a range of spatial frequencies. For motion of the line and grating in opposite directions, summation was never observed. This supports the hypothesis that direction selective mechanisms are responsible for motion perception at threshold. Further analysis of the data produced estimates of the spatial frequency tuning of these mechanisms. A quantitative model is proposed to interpret the data, and it is suggested that flickering gratings are not decomposed into their moving components by the visual system.

Cybernetics↗
PubMed1985

A model of the neural mechanisms responsible for pattern recognition and stimulus specific habituation in toads.

A neural model of the mechanisms possibly responsible for stimulus-specific habituation in toads is proposed. The model follows the hypothesis that prey-predator recognition is performed by command units as a result of retina-tectum-pretectum interaction. The model allow us to study the possible coding that the nervous system of toads uses for different prey stimuli, the neural mechanisms of habituation and dishabituation, and the dynamic changes that the command units may have during these processes. The model proposes specific hypothesis and experiments to clarify the nature of these processes and to test the validity of the command unit hypothesis.

Animals↗
PubMed1985

The application of parametric multichannel spectral estimates in the study of electrical brain activity.

A parametric autoregressive model was applied to the multichannel EEG time series. Small statistical fluctuations of the spectral estimates obtained from the short data strings made possible to follow the time changes of the signals. The multiple and partial coherences were calculated for the four channel process and compared with the coherences computed between the pairs of channels. From the study it followed that the partial coherences are the proper measure of the synchronization of brain structures and their intrinsic relationships. The partial phase spectra give the information about the phase delays. The advantages of the parametric description of signals in the frequency domain in respect to the modelling of dynamic systems was pointed out.

Brain↗
PubMed1985

Human pattern recognition: individually different strategies in analyzing complex stimuli.

Multidimensional scaling experiments were performed with "size" and "brightness" as parameters. Subjects (ss) had to rate the dissimilarity of pairs of discs differing in size or in brightness only, or in both parameters. It was then attempted to find a rule, by which the dissimilarity judgements of two-dimensional differences can be predicted from judgements given for the one-dimensional components. Minkowski-metrics were chosen as models, since for most of the ss the prerequisites for applying these metrics seem to be fulfilled. A simple procedure is described by which the one metric out of all Minkowski-metrics can be found which gives the best description for the data of a subject (Fig. 4). Although the task and the parameters used were the same for all ss, individually best metrics differed considerably, indicating individually different modes of perceptual analysis: Most ss adhered, roughly, to either the City-block or the Euclidean metric (cf. Fig. 10). (Only City-block metric was to be expected, since "size" and "brightness" are generally thought to be "separable" parameters.) In addition, there were three ss with metrics clearly different from both the City-block and the Euclidean metric (best exponents around 1.4). In view of those substantial differences between individuals one has to be cautious against the practice of averaging data from different ss.

Cybernetics↗
PubMed1985

An optimal monitor of the electroencephalographic sigma sleep state.

A model has been proposed for a Markov-jumping sleep depth that modulates a white-noise driven structure generating the sigma rhythm in the electroencephalogram. The corresponding maximum likelihood monitor, that continuously detects the current sleep stage from the observed electroencephalogram, has been derived and implemented. Simulations show high detection performances.

Cybernetics↗
PubMed1985

An analysis of extracellular single muscle fibre action potential field--modelling results.

The radial variability of extracellular single muscle fibre action potential (SFAP) field was studied on the basis of an SFAP theoretical model originally constructed by Rosenfalck (1969). Amplitude and time parameters of the SFAP as a function of the radial distance r less than or equal to 10 mm from the fibre were described by simple mathematical expressions. The results obtained were compared with existing experimental data from different authors and discussed in detail.

Action Potentials↗
PubMed1980

Anthropomorphic robotics. I. Representing mechanical complexity.

A study of the fundamental principles upon which manipulation dexterity is based cannot help mixing robotic and neurophysiological concepts. A preliminary step in this study consists of trying to understand the complexity of manipulation dynamics. Though complexity shows itself in the massive number of elements of kinematic and dynamic equations, the fundamental simplicity of the underlying mechanical laws suggests to look for a structure, particularly from the computational point of view. Accordingly, a working computational model is proposed that organizes the massive computational load into a structure which is composed of a small number of computational units and lends itself to parallel computation.

Arm↗
PubMed1980

Anthropomorphic robotics. II. Analysis of manipulator dynamics and the output motor impedance.

An important factor in trying to capture the complexity of many manipulation problems is the notion of Output Motor Impedance, i.e., the relationship between a set of disturbing forces and the resulting variation in arm configuration. The functional significance of such force/displacement characteristics is investigated, showing how several aspects of different manipulation tasks (holding against gravity, inserting, fast moving, and throwing) can be naturally described in terms of appropriate modulation of the impedance characteristics of the manipulator. For this reason, impedance modulation can be considered an integral part of motor control.

Arm↗