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  • Efferent cerebellar neurones  (2)
  • Conceptual schema analysis  (1)
  • Deafferentation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Requirements engineering 1 (1996), S. 47-62 
    ISSN: 1432-010X
    Keywords: Conceptual schema analysis ; Information system re-engineering ; Reference components ; Similarity measures ; Schema clustering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The paper deals with the problem of building an inventory of information systems for the public administration, with reference to an ongoing project in Italy. We describe the investigation techniques defined for collecting information and the techniques developed for a systematic analysis of the large set of conceptual schemas resulting from the investigation. These schemas describe the data used by the public administration work processes. In particular, we describe the conceptual schema of the inventory, which is the basis for discussing the methodology of investigation, the choice of units of investigation, the data collection and merging, and the access to information. Then, we present the schema analysis techniques developed to analyse semi-automatically the large set of conceptual schemas resulting from the investigation. In particular, we illustrate indexing techniques for identifying representative descriptors of schemas and similarity techniques to compare schemas for their classification into families. Finally, the tool developed to support the storage, analysis and classification of schemas is described and experimentation results are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 57 (1985), S. 370-380 
    ISSN: 1432-1106
    Keywords: Inferior olive ; Purkinje cells ; Efferent cerebellar neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cerebellar units were recorded extracellularly in rats before and after an intraveinous injection of 3-acetylpyridine destroying selectively the IO. All the Purkinje cells show a loss of the complex discharge between 2 h 15 min and 2 h 45 min after treatment. This time, called the “critical period” corresponds to the degeneration of the neurons of the inferior olive as revealed by the decrease of their metabolic activity. The simple spikes of the Purkinje cells increase their discharge frequency soon after the climbing fibers cease firing. On the contrary the firing frequency of the inhibitory interneurons does not show significant changes after degeneration of the inferior olive. The efferent cerebellar neurons, including cells of the cerebellar and vestibular nuclei receiving the axon terminals of the Purkinje cells, decrease their discharge rate up to thirty times during and after the critical period. It is demonstrated that this effect is due to the increased inhibitory activity of the Purkinje cells deafferented from the climbing fibers, whereas the deafferentation of the efferent cerebellar neurones from the collaterals of the olivary cells has little impact.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 59 (1985), S. 404-409 
    ISSN: 1432-1106
    Keywords: Cerebellar inhibition ; Inferior olive ; Efferent cerebellar neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The long term effects of inferior olive destruction on the activities of the Purkinje cells and their target neurones in the cerebellar nuclei were studied in the rat. Careful observations were also made of motor behaviour throughout the study. Albino rats were injected with 3-acetylpyridine to produce a neurotoxic destruction of the inferior olive and then were used for acute recording experiments at 1–2 days, 5–7 days, 12–18 days, 35–38 days, 75–97 days and 230–252 days. After degeneration of the inferior olive, there was an initial period lasting for a few days, characterized by a high firing frequency of Purkinje cells associated with a very low level of activity of the neurones in the cerebellar nuclei. During this period, there was a deep depression of motor activity. A period of adaptation follows during the first month, characterized by a slow recovery of the initial firing frequency of the cerebellar units and a gradual recovery of spontaneous locomotion; nevertheless the firing pattern and motor behaviour remain abnormal. From one month on the unit activities disturbances and the motor deficiencies stabilize. The hypothesis is advanced that Purkinje cell inhibition on their target neurones, which increases during the initial period, gradually diminishes during the adaptation time, and then stabilizes to a subnormal state.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: TTX ; Purkinje cell ; Cerebellum ; Deafferentation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tetrodotoxin (TTX) is widely used to block the sodium dependent action potential in excitable cells to study their other ionic properties. TTX applied outside, selectively blocks voltage dependent sodium channels and is thought to have no other effects. We report here that TTX, applied to slices of rat cerebellum, suppressed sodium spikes of the Purkinje cells and induced firing in bursts of slower spikes. This activity was blocked by cobalt (2 mM) or cadmium (0.2 mM) in the medium as well as by hyperpolarizing currents showing that the slow spikes were due to voltage dependent calcium channels. The membrane potential was not significantly changed by TTX and the spikes during the bursts had the same threshold potentials and peak spike amplitudes as the voltage and Ca2+ dependent dendritic spikes evoked by injected current before adding TTX. This indicated that no marked changes in the membrane conductances were produced by the TTX. Unlike the burst firing induced by removing extracellular sodium, the TTX induced bursts were not followed by a large hyperpolarization. The same kind of results were obtained with extracellular recording in the in-vivo preparation with TTX applied topically or by pressure near the recording sites. TTX induced burst firing was not due to blocking afferent inhibitory input to the PC, since bicuculline (10-6 M) applied without TTX, produced only increased firing of fast action potentials and no bursts. The bursts could be arrested within 1 to 2 min by intravenously administering 2 mg/kg sodium pentobarbital, the blockage lasted from 5 to 15 min. These effects of TTX were not due to a contaminant as TTX from two different suppliers produced the same effects. A possible mechanism based on a decrease of intracellular free sodium is discussed.
    Type of Medium: Electronic Resource
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