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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 1-5 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The recognition of textures involves multiple local filtering and subsequent averaging of the image to produce a feature space in which textures are represented as cluster centers. Results are presented for a two variate algorithm involving the features “brightness” and “roughness”. Both regular and random textures generated by program are used. The final result of classification is expressed in terms of the original textures: the computer “paints” what it has seen — and makes rather understandable errors at the borders between different textures.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 24-29 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A neural net model of discrete populations of formal neurons have been constructed to study evoked potentials based on our previous simulation studies (Anninos, 1972). Some interesting results came up from the examination of our findings regarding the latencies and the period of the cyclic activity of the evoked potentials. In fact, the different successive latencies for the five identical stimuli and the different periods for each of the cyclic activities, all are consequences of inhibitory and excitatory influences from a large neuronal population. Furthermore, such behavior of the system is not only related to the unknown neuronal population but was also substantially altered by what occurred in other systems at the time of stimulus, or prior to it.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 6-23 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Zusammenfassung Ausgehend von den elektrischen Vorgängen an der erregbaren Membran wird der Kodierungsprozeß untersucht. Eine Leitwert-Potential-Beziehung als Bedingung für die Impulsauslösung gestattet eine detaillierte Analyse bei verschiedenen Eingangssignalen. Bei der Ansteuerung mit einem Leitwert erfolgt die Sättigung der Umsetzungskennlinie des Kodierers erheblich früher als bei Stromeingang. Auch das Phänomen des over-stretch wird vom Modell erklärt. Zur Kleinsignalanalyse wird die Theorie der Systeme mit zeitvariablen Parametern angewendet. Die Übertragungsfunktion des Kodierers setzt sich in vielen Fällen additiv aus denen mehrerer Leckstrom-Integratoren mit unterschiedlichen Zeitkonstanten zusammen. Auch die teilweise beobachtete Abhängigkeit der Parameter von der Trägerfrequenz wird modellmäßig erfaßt. Die Adaptationsvorgänge im Kodierer beruhen auf einer intracellulären Anhäufung von Natriumionen während der Impulsabgabe. Die Aktivierung der Ionenpumpe bewirkt einen zusätzlichen Stromfluß, wodurch sich die abgegebene Impulsfrequenz verringert. Bei größeren Ansteuerungen trägt die durch langsame Kalium- und Natriuminaktivierung auftretende Verschiebung der Impulsauslösecharakteristik ebenfalls zur Adaptation bei. Die Betrachtungen, obwohl allgemeingültig für den biologischen Mechanismus der Impulsentstehung und Kodierung, wurden im Rahmen der Arbeit nur auf experimentelle Befunde an Receptorneuronen begrenzt. Für das Motoneuron und Neuronen in verarbeitenden Schichten müssen zusätzlich die Summation synaptischer Vorgänge und statistische Verknüpfungen zwischen Eingangs- und Ausgangssignal berücksichtigt werden.
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  • 4
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Starting with the assumption that the output of a biological transducer is the linear sum of discrete waveshapes, then under appropriate conditions, such a system may be modelled by a transfer function whose input is a train of delta functions. The transfer function is obtained by averaging over the population of possible waveshapes. The representation of the input as a train of delta functions facilitates the calculation of its frequency power spectrum. A number of examples of possible physiological interest are given.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 53-54 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
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  • 6
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The introduction (A) is followed by parts B and C in which active movements of the tibia are recorded from intact legs and legs with cut receptor tendons (tendon of the femoral chordotonal organ). For this purpose the femur is fixed and then either the movement of the freely moving tibia is filmed or the force produced by the fixed tibia is measured directly. Leg movements caused by touching the abdomen (active movements) are faster than movements which are caused by stretching and releasing the femoral chordotonal organ in inactive animals. After an active movement the return to the starting-point is similar to that following a passive displacement: the speed of the backward movement is very low in intact legs, but relatively high in legs with cut receptor tendons. In intact legs the speed of the return to the starting-point shows a correlation between active and passive movements. A preliminary discussion of these movements is given in (D). It is followed in Section E by a description of the movements of the femur-tibia-joint of intact legs and legs with cut receptor tendons in free-walking animals. Cutting the receptor-tendon does not enlarge the amplitude very significantly. In Section F the receptor tendon is sinusoidally moved during active movements. The result of such an experiment upon inactive animals is quite different. No reaction can be observed during active movements at that phase position for which the response occures in inactive animals. But there is an alternative reaction with the same frequency as the stimulus. In active animals the amplitude of the reaction is very irregular, but normally larger than in inactive animals. Sometimes one reaction is omitted or there is more than one reaction per stimulus-cycle. The phase-shift is significantly larger than in inactive animals. In Section D a hypothesis for the control of active movements is discussed. According to this hypothesis the control system of the “Kniesehnenreflex” is switched off during active movements. The set-point of the system (the starting-point) is not altered by an active movement. The beginning of flexion and/or extension of the femur-tibia-joint and the maximum speed of the movements are at least partially influenced by the femoral chordotonal organ. The amount of this influence is variable.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 81-94 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract This paper pursues three basic definitions of comparative information motivated by various theories of information. The first definition involves the ordering of experiments according to a qualitative relation “not more informative than”, the second is derived from measure-theoretic properties of information without probability leading to a construction of a partially ordered algebra of information, the third is based on a particular aspect of qualitative semantic information involving the ordering of propositions according to their information content. This approach leads to a Boolean interpretation of informative propositions generating a qualitative probability structure. Some ways are discussed how to represent informative propositions by compatible normed information measures, leading to a measure of probability in terms of information.
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  • 8
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract It is proposed that distinct anatomical regions of cerebral cortex and of thalamic nuclei are functionally two-dimensional. On this view, the third (radial) dimension of cortical and thalamic structures is associated with a redundancy of circuits and functions so that reliable signal processing obtains in the presence of noisy or ambiguous stimuli. A mathematical model of simple cortical and thalamic nervous tissue is consequently developed, comprising two types of neurons (excitatory and inhibitory), homogeneously distributed in planar sheets, and interacting by way of recurrent lateral connexions. Following a discussion of certain anatomical and physiological restrictions on such interactions, numerical solutions of the relevant non-linear integro-differential equations are obtained. The results fall conveniently into three categories, each of which is postulated to correspond to a distinct type of tissue: sensory neo-cortex, archior prefrontal cortex, and thalamus. The different categories of solution are referred to as dynamical modes. The mode appropriate to thalamus involves a variety of non-linear oscillatory phenomena. That appropriate to archior prefrontal cortex is defined by the existence of spatially inhomogeneous stable steady states which retain contour information about prior stimuli. Finally, the mode appropriate to sensory neo-cortex involves active transient responses. It is shown that this particular mode reproduces some of the phenomenology of visual psychophysics, including spatial modulation transfer function determinations, certain metacontrast effects, and the spatial hysteresis phenomenon found in stereopsis.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 13 (1973), S. 223-227 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A general characterization of multi-input movement detection models is given in terms of the Volterra series formalism. When nonlinearities of order higher than the second are negligible, an n-input system can be decomposed into a set of 2-input systems, summing linearly. For a (symmetrical) 2-input system which has significant nonlinearities only up to the second order, the correlation model is its most general expression, if the infinite time average of the output is taken. Specific observations from optomotor experiments (e.g. phase invariance and contrast frequency dependence) can be interpreted in a general way in terms of properties of the Volterra representation.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 21 (1976), S. 161-170 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A network is discussed that is selectively sensitive to the direction of moving patterns. The network is studied by means of computer simulation. It is shown that the network can be used as a paradigm for information processing at ganglion cell level in the retina of certain mammals. The responses of the network are in good qualitative agreement with results obtained by Michael (1968) on the ground squirrel. The connectivity of the network conforms to known retinal structure. The directionally sensitive property of the network is the result of the connectivity of the “inner plexiform layer”. Retinal cells distal to the ganglion cells are not committed to any directional sensitivity.
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