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  • 1
    Electronic Resource
    Electronic Resource
    Simulander: A neural network model for the orientation movement of salamanders (1995)
    Springer
    Journal of comparative physiology 176 (1995), S. 379-389 
    Details
    ISSN: 1432-1351
    Keywords: Neural network ; Evolution strategy ; Salamander ; Optic tectum ; Orienting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Simulander is a feedforward neural network simulating the orientation movement of salamanders. The orientation movement is part of the prey capture behavior; it is performed with the head alone. Simulander is a network which consists of 300 neurons incorporating several cytoarchitectonic and electrophysiological features of the salamander brain. The network is trained by means of an evolution strategy. Although only 100 tectum neurons with fairly large receptive fields are used (“coarse coding”), Simulander is able to localize an irregularly moving prey precisely. It is demonstrated that large receptive field neurons are important for successful prey localization. The removal of a model tectum hemisphere leads to a network which accounts for investigations made in living monocular salamanders. The model also yields an understanding of electrical stimulation experiments in toads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219063
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  • 2
    Electronic Resource
    Electronic Resource
    Modulation of mRNA expression of the neurotrophins of the nerve growth factor family and their receptors in the septum and hippocampus of rats after transient postnatal thyroxine treatment I. Expression of nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin 4 mRNA (1998)
    Springer
    Experimental brain research 119 (1998), S. 1-8 
    Details
    ISSN: 1432-1106
    Keywords: Key words Thyroid hormone ; Neurotrophins ; Septum ; Hippocampus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Early postnatal application of thyroid hormones to rats results in morphological changes in septum and hippocampus. Modulation in the expression of either neurotrophins and/or their receptors is postulated to be responsible for these effects. In the present study we tested whether thyroxine administration leads to changes in the expression of neurotrophins of the nerve growth factor (NGF) family. Newborn rats were treated daily with subcutaneous injections of thyroxine until postnatal day (P) 12 at maximum. The pups were killed at defined intervals from P2 to 21. The septal area and the hippocampi were analyzed using the reverse transcriptase-PCR method for quantitation of NGF, brain-derived neurotrophic factor (BDNF), NT-3, and NT-4 messenger RNA (mRNA) levels. In hippocampus of hyperthyroid rats, as compared to controls, we found higher levels of BDNF and NT-3 mRNA over the total investigation period, whereas in the septum a thyroxine-dependent increase in NT-3 mRNA expression was observed. In addition, significant thyroxine-induced effects were found for all variables (except for NGF in the septum) at particular postnatal days. From these data we conclude that modulation of neurotrophin expression is a possible mechanism for the morphological modifications within the hippocampal mossy fiber system and the septohippocampal cholinergic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050313
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  • 3
    Electronic Resource
    Electronic Resource
    Modulation of mRNA expression of the neurotrophins of the nerve-growth-factor family and their receptors in the septum and hippocampus of rats after transient postnatal thyroxine treatment. II. Effects on p75 and trk receptor expression (1999)
    Springer
    Experimental brain research 127 (1999), S. 307-313 
    Details
    ISSN: 1432-1106
    Keywords: Key words Thyroid hormone ; RT-PCR ; p75 receptor ; trkA ; trkB ; trkC ; Septum ; Hippocampus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Early postnatal application of thyroid hormones to rats results in morphological changes of the septo-hippocampal cholinergic and the hippocampal mossy fiber systems. Modulation in the expression of either neurotrophins and/or their receptors is postulated to be involved in these effects. In a recent study, we showed that, after thyroxine application, the mRNA expression of neurotrophins of the nerve-growth-factor (NGF) family is significantly upregulated both in septum and hippocampus. To test whether the neurotrophin receptors (the low-affinity neurotrophin receptor p75 and the specific high-affinity receptors trkA, trkB, and trkC) were also affected by hormone administration, newborn rats were treated daily with subcutaneous injections of thyroxine until postnatal day 12 (P12) at latest. Control animals received corresponding injections of saline. The pups were sacrificed at defined intervals from P9 to P14. The septal areas and the hippocampi were analyzed using the reverse-transcription polymerase chain reaction (RT-PCR) method for quantification of p75, trkA, trkB, and trkC mRNA levels. Analysis of variance over the total investigation period revealed no significant general increases of the gene expressions of either neurotrophin receptor, neither in the septum nor in the hippocampus, although previous results have shown marked changes in neurotrophin levels. On particular postnatal days, significant upregulation could be observed in hippocampus for trkB and trkC. From these and recent data, we conclude that modulation of neurotrophin expression rather than neurotrophin-receptor expression contributes to the morphological modifications within the hippocampal mossy fiber system and the septo-hippocampal cholinergic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050800
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  • 4
    Electronic Resource
    Electronic Resource
    The Acoustic Startle Response in Inbred Roman High- and Low-Avoidance Rats (1997)
    Springer
    Behavior genetics 27 (1997), S. 579-582 
    Details
    ISSN: 1573-3297
    Keywords: Acoustic startle response ; sensitization ; amygdala ; Roman high- and low-avoidance rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract To investigate the emotional reactions of two rat strains selectively bred for good and poor two-way avoidance acquisition (RHA/Verh and RLA/Verh), male animals of both strains were tested in an acoustic startle response test. They received 40 acoustic stimuli followed by 10 electric foot shocks and another 30 acoustic stimuli. RLA/Verh rats showed a significantly higher startle response compared to RHA/Verh animals, indicating a stronger emotional reaction to acoustic stimuli. In addition, the former showed a stronger response to foot shocks. Combined with earlier findings, we conclude that selection for two-way avoidance learning does not result in cognitive defects in the RLA/Verh strain but, rather, in stronger emotional reactions to fearful stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021465217299
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of Two Sensitization Paradigms of the Acoustic Startle Response in Wistar and Sprague–Dawley Rats (1999)
    Springer
    Behavior genetics 29 (1999), S. 59-63 
    Details
    ISSN: 1573-3297
    Keywords: Acoustic startle response ; habituation ; sensitization ; fear ; genetic differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract An increase in general responsiveness after aversive stimulation has provided a most widely accepted and well-understood sensitization paradigm. According to a second paradigm (based on the dual process theory of habituation and sensitization), not only additional aversive stimuli, but also the response-eliciting stimuli themselves, induce sensitization. To relate these two sensitization paradigms, we compared the course of startle response parameters during repetitive acoustic stimulation with the change in startle amplitude after electric footshocks in outbred Wistar and Sprague–Dawley rats. Compared to the Wistar rats used, the Sprague–Dawley rats showed a lower response decrement and a shortened latency during repetitive stimulation, both of which are indicators of increased sensitization by the startle-eliciting stimuli. In addition, the Sprague–Dawley rats also demonstrated a reduced increase in startle amplitude following footshock. This was postulated to be a consequence of the strong sensitization by startle-eliciting stimuli, which interferes with sensitization elicited by footshock. Because our Wistar and Sprague–Dawley rats did not differ in initial startle amplitude, but mainly in susceptibility to sensitization, further comparisons of these genetically different stocks of rats seem to be of potential value in studying differences in fear-motivated behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021442006821
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