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Poster presentation at 1st International Workshop on Odor Spaces.
Mice are exceptional in their ability to capture their chemical environment, mapping the olfactory world into a basic sensory representation with over one thousand different types of chemical sensors, that is, olfactory sensory neurons (OSNs). OSNs of each type converge in the olfactory bulb onto exclusive distinct physiological areas called glomeruli. The glomeruli constitute the first relay station of olfactory stimulus representation in the mouse brain. Thus, the stimulus induced glomerular input pattern spatially embodies an important part of the sensory representation in the olfactory bulb. Still, topographic organization principles (chemotopy, tunotopy) are under debate. One reason might be that investigation are, due to experimental limitations, only performed on stimuli sets in the size of one hundred odors. But this represents only a tiny snapshot of the vast amount of molecules in the olfactory world and topographic relationships might be disguised in the incomplete representation of molecular receptive ranges (MRR). Therefore we investigated the problem with the MOR18-2 glomerulus as point of reference: First we determined it's MRR. Then, based on a measurement set covering this MRR, we elucidated the topographic embedding. It shows that MOR18-2 is embedded in a hierarchy of patchy tunotopic domains.
We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n_TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process.
Poster presentation at The Twenty Third Annual Computational Neuroscience Meeting: CNS*2014 Québec City, Canada. 26-31 July 2014: We study random strongly heterogeneous recurrent networks of firing rate neurons, introducing the notion of cohorts: groups of co-active neurons, who compete for firing with one another and whose presence depends sensitively on the structure of the input. The identities of neurons recruited to and dropped from an active cohort changes smoothly with varying input features. We search for network parameter regimes in which the activation of cohorts is robust yet easily switchable by the external input and which exhibit large repertoires of different cohorts. We apply these networks to model the emergence of orientation and direction selectivity in visual cortex. We feed these random networks with a set of harmonic inputs that vary across neurons only in their temporal phase, mimicking the feedforward drive due to a moving grating stimulus. The relationship between the phases that carries the information about the orientation of the stimulus determines which cohort of neurons is activated. As a result the individual neurons acquire non-monotonic orientation tuning curves which are characterized by high orientation and direction selectivity. This mechanism of emergence for direction selectivity differs from the classical motion detector scheme, which is based on the nonlinear summation of the time-shifted inputs. In our model these two mechanisms coexist in the same network, but can be distinguished by their different frequency and contrast dependences. In general, the mechanism we are studying here converts temporal phase sequence into population activity and could therefore be used to extract and represent also various other relevant stimulus features.
Based on a non-rigorous formalism called the “cavity method”, physicists have made intriguing predictions on phase transitions in discrete structures. One of the most remarkable ones is that in problems such as random k-SAT or random graph k-coloring, very shortly before the threshold for the existence of solutions there occurs another phase transition called condensation [Krzakala et al., PNAS 2007]. The existence of this phase transition seems to be intimately related to the difficulty of proving precise results on, e. g., the k-colorability threshold as well as to the performance of message passing algorithms. In random graph k-coloring, there is a precise conjecture as to the location of the condensation phase transition in terms of a distributional fixed point problem. In this paper we prove this conjecture, provided that k exceeds a certain constant k0.
Impairment in past tense production as well as interaction between tense and aspect have been found in both fluent and non-fluent aphasia (e.g. Dragoy & Bastiaanse, 2013). Inflection has been found to be relatively preserved in semantic dementia (SD) (Thompson et al., 2012). The aims of the present study are a) to compare the morphosyntactic abilities of patients with aphasia and SD in tense and aspect marking and b) to explore the interaction of lexical (+/- telic) and grammatical (perfective/imperfective) aspect in aphasia and SD. A sentence completion task was administered to 30 native speakers of Greek: 10 patients with aphasia (6 anomic, 2 Wernicke and 2 agrammatic), 10 age and education-matched controls, 5 patients with SD and 5 controls. The material consisted of unergative, unaccusative and transitive verbs (12 of each verb class) and the participants had to apply present (imperfective) and past (perfective) tense. Unergative and unaccusative verbs differ in terms of their aspectual properties with the unergative being [-telic], and unaccusative [+telic]. Transitive verbs vary. A principal distinction between the tested conditions was the standard ummarked combination ([+telic] verbs in past perfective and [–telic] verbs in present imperfective) vs. the marked one ([+telic] verbs in present imperfective and [–telic] in past perfective). Both control groups performed at ceiling in all conditions. Aphasic participants were significantly more impaired than the control group in all conditions. SD participants were significantly more impaired than the controls only in the production of present tense (M-W U= 1.5, p= 0.024). There was no difference between past perfective and present imperfective for neither group, but there was an interaction between verb class and tense for the aphasic participants, as performance in unaccusative verbs in past perfective (unmarked condition) was significantly better than in unergatives in past perfective (marked condition) (Z=2.512, p=0.012) but performance in unaccusatives in present imperfective (marked condition) was significantly worse than performance in unergatives in present imperfective (unmarked condition) (Z=2.680, p=0.004). In sum, aphasic participants performed significantly better in the unmarked than in the marked conditions. Such an interaction was not found for the SD group. Aphasic participants performed significantly worse than the SD subjects in past perfective tense (M-W U= 7.5, p=0.029) in total, and the difference was significant only for unaccusative verbs (M-W U= 6.5, p=0.021), although both groups performed very well in this condition. There was no difference in present, neither for each verb class separately nor for the total score. A general past tense deficit cannot be upheld for either group. Rather, SD participants appear relatively impaired in producing present tense. We argue for slight morphosyntactic impairment in SD, although with a different underlying cause than in aphasia. Moreover, our data suggest an effect of aspectual markedness in aphasia but not in SD. We discuss this finding in the light of the different neuropathology of the two populations.
Zum Themenfeld "Diversität und Vielfalt" diskutierten im Rahmen des 8. Treffens des Nachwuchsnetzwerkes "Stadt, Raum, Architektur" Wissenschaftler_innen aus den Sozial-, Geistes- und Raumwissenschaften an den Instituten für Humangeographie, Kulturanthropologie und Europäische Ethnologie der Goethe-Universität Frankfurt am Main am 9. und 10. November 2012. Vor dem Hintergrund aktueller Debatten um die Konzeptualisierung von sowie den praktischen Umgang mit soziokultureller Vielfalt fand ein produktiver Austausch aus den Perspektiven der Stadtplanung, der Architekturwissenschaft sowie der sozial- und kulturwissenschaftlichen Stadt- und Raumforschung statt. Die Ergebnisse dieser interdisziplinären Auseinandersetzung hinsichtlich einer globalen Diskursverschiebung von "Multikulturalismus" zu "Diversität" und der Adaption entsprechender Strategien in Politik, Wirtschaft und Gesellschaft werden in diesem Tagungsbericht anhand theoretischer Ansätze zu "Super-Diversity", Kosmopolitismus und Transnationalismus diskutiert. Empirisch werden insbesondere Fragen zu Standortmarketing, Integrationspolitiken und der Verräumlichung von Diversität sowie konkreter Praktiken der Segregation, Marginalisierung und Aushandlung von Differenz aufgegriffen. Abschließend wird die Frage nach Konflikten und Potenzialen einer "neuen Diversität" aus stadtplanerischer, dekolonialer und poststrukturalistischer Perspektive diskutiert.