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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 83 (2000), S. 301-312 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  A computational model of the lesion and single unit data from navigation in rats is reviewed. The model uses external (visual) and internal (odometric) information from the environment to drive the firing of simulated hippocampal place cells. Constraints on the functional form of these inputs are drawn from experiments using an environment of modifiable shape. The place cell representation is used to guide navigation via the creation of a representation of goal location via Hebbian modification of synaptic strengths. The model includes consideration of the phase of firing of place cells with respect to the theta rhythm of hippocampal EEG. A series of predictions for behavioural and single-unit data in rats are derived from the input and output representations of the model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 117 (1997), S. 131-142 
    ISSN: 1432-1106
    Keywords: Key words Hippocampus ; Place cells ; Idiothetic cues ; Interoceptive and exteroceptive cues ; Path integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Pyramidal cells in the rat hippocampus fire whenever the animal is in a particular place, suggesting that the hippocampus maintains a representation of the environment. Receptive fields of place cells (place fields) are largely determined by the distance of the rat from environmental walls. Because these walls are sometimes distinguishable only by their orientation with respect to the outside room, it has been hypothesised that a polarising directional input enables the cells to locate their fields off–centre in an otherwise symmetrical environment. We tested this hypothesis by gaining control of the rat’s internal directional sense, independently of other cues, to see whether manipulating this sense could, by itself, produce a corresponding alteration in place field orientation. Place cells were recorded while rats foraged in a rectangular box, in the absence or presence of external room cues. With room cues masked, slow rotation of the rat and the box together caused the fields to rotate accordingly. Rotating the recording box alone by 180° rarely caused corresponding field rotation, while rotating the rat alone 180° outside the environment and then replacing it in the recording box almost always resulted in a corresponding rotation of the fields. This shows that place field orientation can be controlled by controlling the internal direction-sense of the rat, and it opens the door to psychophysical exploration of the sensory basis of the direction sense. When room cues were present, distal visual cues predominated over internal cues in establishing place field orientation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    BJOG 109 (2002), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective To investigate whether the intravenous urogram used in an appropriate setting is a valuable investigation for managing severe loin pain in pregnancy.Design Prospective obsevational study.Setting University teaching hospital.Population Fifteen pregnant women referred with severe loin pain.Methods A prospective study collecting data over a 24-month period was performed. Women with severe loin pain believed to be of renal origin that had failed to respond to conservative treatment were referred by their obstetricians. The intravenous urogram was performed that consisted of a two-film series (plain film and a 20-minute postmicturition film).Main outcome measures Management of severe loin pain in pregnancy based on the findings of the intravenous urogram.Results Over the two-year period, 15 women had an intravenous urogram performed at a median gestation of 32 weeks (24–36 weeks). All women had undergone a prior urinary tract ultrasound examination within 24 hours of referral, which showed dilatation on the symptomatic side in 15/15 cases. The intravenous urogram confirmed dilatation on the ipsilateral side in 14/15 cases and revealed the level of dilatation in all of these cases. Delayed excretion of contrast was seen in all 14/15 cases. Three patients had obstructing ureteric calculi revealed by the intravenous urogram and one patient had a non-dilated and non-obstructed system.Conclusions An intravenous urogram is a safe investigation in the appropriate setting. It allows for an accurate diagnosis to be made and for appropriate treatment to be instigated with joint decisions from urologic, obstetric and radiologic teams. This multidisciplinary approach care can be specifically tailored to the individual patient, which we feel is safer for both mother and baby.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sir It is vital to try to conserve biological diversity, but to do this we must know where it is. New databases mapping African biodiversity now offer this information. Quantitative analyses of these data reveal geographical priorities for conservation broadly matching ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 425 (2003), S. 828-832 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the brain, hippocampal pyramidal cells use temporal as well as rate coding to signal spatial aspects of the animal's environment or behaviour. The temporal code takes the form of a phase relationship to the concurrent cycle of the hippocampal electroencephalogram theta rhythm. These two ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 416 (2002), S. 90-94 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The hippocampus is widely believed to be involved in the storage or consolidation of long-term memories. Several reports have shown short-term changes in single hippocampal unit activity during memory and plasticity experiments, but there has been no experimental demonstration of long-term ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 425-428 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Place cells were recorded from six rats foraging for food in four boxes (a small square, SS; large square, LS; horizontal rectangle, HR; and vertical rectangle, VR) located within a rectangular testing room oriented north-south (Fig. 1). We first investigated whether the location of peak firing in ...
    Type of Medium: Electronic Resource
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  • 8
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    New York : Periodicals Archive Online (PAO)
    Journal of Memory and Language. 31:4 (1992:Aug.) 429 
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