Palmefugl for askekrukke: I anledning af reformationsåret 2017

Intet resum

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Tycho Brahes supernova i 1572 set med samtidens øjne. Religiøse og astronomiske tolkninger hos Georg Busch og Rasmus Hansen Reravius

NB: Artiklen er på dansk, kun resuméet er på engelsk.The appearance of the supernova in 1572 gave rise to a series of publications on the unknown heavenly body’s nature and significance. The most famous is the work by Danish astronomer Tycho Brahe, De nova stella, in which the author maintained that it must be a question of a new star. But even though Tycho’s observations had far-reaching implications for the history of science, there were other contemporary interpretations of the heavenly phenomenon that attracted greater public attention. Georg Busch, a German painter, was one of the first to write about the phenomenon. According to Busch, it was a comet. He further claimed that it had been created by human sin having generated steam made up of impurities that, condensed into a tight ball, had risen into the air, where it was ignited by oxygen as a comet. Busch’s book was very popular in Germany and in Scandinavia as well, where it was published in a translation by a clergyman, Rasmus Hansen Reravius (Danish was also the written language in Norway at the time) and in a Swedish translation based on Reravius’ work. Reravius, however, published his work after Tycho, to whom Reravius refers indirectly, had made his theory public. As a result, Reravius emphasised the phrase “new start” in his title and preface and is therefore one of the first popularising authors in whose work a spillover from Tycho’s observations is evident. Reravius’ intention was, however, certainly not to make Tycho’s astronomy better known but, on the contrary, to preach repentance and penance to the population, since, for Scandinavian readers, he had put forward Busch’s interpretation of the “comet.” This interpretation, according to which the comet was not only a warning sign from God to humankind but that it had been actually, physically created by sin, does not seem to have spread very far in Europe generally but was apparently particularly appealing to Lutheran society in the 1500s. In any case, it is only in these countries that the theory was proposed, first and foremost through Busch and his Nordic translators. Closer examination of these publications thus gives us not only an insight into how new knowledge was disseminated in the 1500s. In a broader perspective, it also gives an insight into the Protestant world of ideas, in which religious and scientific explanations were interwoven