Formation of temporal-feature maps by axonal propagation of synaptic learning

Computational maps are of central importance to a neuronal representation of the outside world. In a map, neighboring neurons respond to similar sensory features. A well studied example is the computational map of interaural time differences (ITDs), which is essential to sound localization in a variety of species and allows resolution of ITDs of the order of 10 μs. Nevertheless, it is unclear how such an orderly representation of temporal features arises. We address this problem by modeling the ontogenetic development of an ITD map in the laminar nucleus of the barn owl. We show how the owl's ITD map can emerge from a combined action of homosynaptic spike-based Hebbian learning and its propagation along the presynaptic axon. In spike-based Hebbian learning, synaptic strengths are modified according to the timing of pre- and postsynaptic action potentials. In unspecific axonal learning, a synapse's modification gives rise to a factor that propagates along the presynaptic axon and affects the properties of synapses at neighboring neurons. Our results indicate that both Hebbian learning and its presynaptic propagation are necessary for map formation in the laminar nucleus, but the latter can be orders of magnitude weaker than the former. We argue that the algorithm is important for the formation of computational maps, when, in particular, time plays a key role.

Cellular mechanisms for resolving phase ambiguity in the owl's inferior colliculus

Both mammals and birds use the interaural time difference (ITD) for localization of sound in the horizontal plane. They may localize either real or phantom sound sources, when the signal consists of a narrow frequency band. This ambiguity does not occur with broadband signals. A plot of impulse rates or amplitude of excitatory postsynaptic potentials against ITDs (ITD curve) consists of peaks and troughs. In the external nucleus (ICX) of the owl's inferior colliculus, ITD curves show multiple peaks when the signal is narrow-band, such as tones. Of these peaks, one occurs at ITDi, which is independent of frequency, and others at ITDi ± T, where T is the tonal period. The ITD curve of the same neuron shows a large peak (main peak) at ITDi and no or small peaks (side peaks) at ITDi ± T, when the signal is broadband. ITD curves for postsynaptic potentials indicate that ICX neurons integrate the results of binaural cross-correlation in different frequency bands. However, the difference between the main and side peaks is small. ICX neurons further enhance this difference in the process of converting membrane potentials to impulse rates. Inhibition also appears to augment the difference between the main and side peaks.

Developmental expression of two Haliotis asinina hemocyanin isoforms

Hemocyanins are large copper-containing respiratory proteins that play a role in oxygen transport in many molluscs. In some species only one hemocyanin isoform is present while in others two are expressed. The physiological relevance of these isoforms is unclear and the developmental and tissue-specific expression of hemocyanin genes is largely unknown. Here we show that two hemocyanin genes in the gastropod Haliotis asinina, which encode H. asinina hemocyanin (HaH1) and HaH2 isoforms, are developmentally expressed. These genes initially are expressed in a small number of mesenchyme cells at trochophore and pre-torsional veliger stages, with HaH1 expression slightly preceding HaH2. These cells largely are localized to the visceral mass, although a small number of cells are present in head and foot regions. Following metamorphosis the isoforms show overlapping as well as isoform-specific expression profiles, suggesting some degree of isoform-specific function.

The verbal transformation effect:an exploration of the perceptual organization of speech

Six experiments investigated the influence of several grouping cues within the framework of the Verbal Transformation Effect (VTE, Experiments 1 to 4) and Phonemic Transformation Effect (PTE, Experiments 5 and 6), where listening to a repeated word (VTE) or sequence of vowels (PTE) produces verbal transformations (VTs). In Experiment 1, the influence of F0 frequency and lateralization cues (ITDs) was investigated in terms of the pattern of VTs. As the lateralization difference increased between two repeating sequences, the number of forms was significantly reduced with the fewest forms reported in the dichotic condition. Experiment 2 explored whether or not propensity to report more VTs on high pitch was due to the task demands of monitoring two sequences at once. The number of VTs reported was higher when listeners were asked to attend to one sequence only, suggesting smaller attentional constraints on the task requirements. In Experiment 3, consonant-vowel transitions were edited out from two sets of six stimuli words with ‘strong’ and ‘weak’ formant transitions, respectively. Listeners reported more forms in the spliced-out than in the unedited case for the strong-transition words, but not for those with weak transitions. A similar trend was observed for the F0 contour manipulation used in Experiment 4 where listeners reported more VTs and forms for words following a discontinuous F0 contour. In Experiments 5 and 6, the role of F0 frequency and ITD cues was investigated further using a related phenomenon – the PTE. Although these manipulations had relatively little effect on the number of VTs and forms reported, they did influence the particular forms heard. In summary, the current experiments confirmed that it is possible to successfully investigate auditory grouping cues within the VTE framework and that, in agreement with recent studies, the results can be attributed to the perceptual re-grouping of speech sounds.

Measuring the Diversity and the Integration of Film Production in Mercosur: A Social Network Analysis

Based on an original and comprehensive database of all feature fiction films produced in Mercosur between 2004 and 2012, the paper analyses whether the Mercosur film industry has evolved towards an integrated and culturally more diverse market. It provides a summary of policy opportunities in terms of integration and diversity, emphasizing the limiter role played by regional policies. It then shows that although the Mercosur film industry remains rather disintegrated, it tends to become more integrated and culturally more diverse. From a methodological point of view, the combination of Social Network Analysis and the Stirling Model opens up interesting research tracks to analyse creative industries in terms of their market integration and their cultural diversity.

Specific JAK2 mutation (JAK2R683) and multiple gene deletions in Down syndrome acute lymphoblastic leukemia

Children with Down syndrome (DS) have a greatly increased risk of acute megakaryoblastic leukemia (AMKL) and acute lymphoblastic leukemia (ALL). Both DS-AMKL and the related transient myeloproliferative disorder (TMD) have GATA1 mutations as obligatory, early events. To identify mutations contributing to leukemogenesis in DS-ALL, we undertook sequencing of candidate genes, including FLT3, RAS, PTPN11, BRAF, and JAK2. Sequencing of the JAK2 pseudokinase domain identified a specific, acquired mutation, JAK2R683, in 12 (28%) of 42 DS-ALL cases. Functional studies of the common JAK2R683G mutation in murine Ba/F3 cells showed growth factor independence and constitutive activation of the JAK/STAT signaling pathway. High-resolution SNP array analysis of 9 DS-ALL cases identified additional submicroscopic deletions in key genes, including ETV6, CDKN2A, and PAX5. These results infer a complex molecular pathogenesis for DS-ALL leukemogenesis, with trisomy 21 as an initiating or first hit and with chromosome aneuploidy, gene deletions, and activating JAK2 mutations as complementary genetic events. (Blood. 2009; 113: 646-648)

Characterization and Quantification of Major Biochemical Components and Secondary Metabolites of Some Green and Red Seaweeds from the Kerala Coast

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Spiking neuron models of the medial and lateral superior olive for sound localisation

Sound localisation is defined as the ability to identify the position of a sound source. The brain employs two cues to achieve this functionality for the horizontal plane, interaural time difference (ITD) by means of neurons in the medial superior olive (MSO) and interaural intensity difference (IID) by neurons of the lateral superior olive (LSO), both located in the superior olivary complex of the auditory pathway. This paper presents spiking neuron architectures of the MSO and LSO. An implementation of the Jeffress model using spiking neurons is presented as a representation of the MSO, while a spiking neuron architecture showing how neurons of the medial nucleus of the trapezoid body interact with LSO neurons to determine the azimuthal angle is discussed. Experimental results to support this work are presented.

A comparison of sound localisation techniques using cross-correlation and spiking neural networks for mobile robotics

This paper outlines the development of a crosscorrelation algorithm and a spiking neural network (SNN) for sound localisation based on real sound recorded in a noisy and dynamic environment by a mobile robot. The SNN architecture aims to simulate the sound localisation ability of the mammalian auditory pathways by exploiting the binaural cue of interaural time difference (ITD). The medial superior olive was the inspiration for the SNN architecture which required the integration of an encoding layer which produced biologically realistic spike trains, a model of the bushy cells found in the cochlear nucleus and a supervised learning algorithm. The experimental results demonstrate that biologically inspired sound localisation achieved using a SNN can compare favourably to the more classical technique of cross-correlation.

Using the interaural time difference and cross-correlation to localise short-term complex noises

The mammalian binaural cue of interaural time difference (ITD) and cross-correlation have long been used to determine the point of origin of a sound source. The ITD can be defined as the different points in time at which a sound from a single location arrives at each individual ear [1]. From this time difference, the brain can calculate the angle of the sound source in relation to the head [2]. Cross-correlation compares the similarity of each channel of a binaural waveform producing the time lag or offset required for both channels to be in phase with one another. This offset corresponds to the maximum value produced by the cross-correlation function and can be used to determine the ITD and thus the azimuthal angle θ of the original sound source. However, in indoor environments, cross-correlation has been known to have problems with both sound reflections and reverberations. Additionally, cross-correlation has difficulties with localising short-term complex noises when they occur during a longer duration waveform, i.e. in the presence of background noise. The crosscorrelation algorithm processes the entire waveform and the short-term complex noise can be ignored. This paper presents a technique using thresholding which enables higher-localisation abilities for short-term complex sounds in the midst of background noise. To determine the success of this thresholding technique, twenty-five sounds were recorded in a dynamic and echoic environment. The twenty-five sounds consist of hand-claps, finger-clicks and speech. The proposed technique was compared to the regular cross-correlation function for the same waveforms, and an average of the azimuthal angles determined for each individual sample. The sound localisation ability for all twenty-five sound samples is as follows: average of the sampled angles using cross-correlation: 44%; cross-correlation technique with thresholding: 84%. From these results, it is clear that this proposed technique is very successful for the localisation of short-term complex sounds in the midst of background noise and in a dynamic and echoic indoor environment.

Kryzys demokracji liberalnej - wybrane problemy rządzenia, legitymizacji i reprezentacji

Główna problematyka zawarta w tekście dotyczy: (1) znaczenia i zakresu kryzysu w gospodarce i polityce, (2) przyjęcia przez państwo i społeczeństwo logiki racjonalności ekonomicznej jako paradygmatu postępowania, (3) przewartościowania pojęcia polityki, co wiąże się m.in. z przyjęciem przez rządzących roli zarządców wybranych sfer państwa oraz z posługiwaniem się przez nich logiką „mieszanej racjonalności” („logiką władzy” i „logiką racjonalności ekonomicznej”), (4) wyzwań związanych z dystrybucją dóbr, (5) reprezentacji i legitymizacji w demokracji liberalnej. Gospodarka kapitalistyczna wpływa na wszystkie sfery życia społecznego, co zmusza do przedstawienia jej „modus operandi”. Charakterystyczne cechy oddziaływania to: (1) racjonalność formalna, (2) dogmat efektywności i ilościowej mierzalności, (3) reprodukcja ideologii mówiącej o wolnej woli jednostki, niezależnie od kontekstu społecznego, (4) wymuszanie odpowiedniej dla siebie reprodukcji siły roboczej, (5) kolonizacja kolejnych sfer aktywności społecznej (np. edukacji i szkolnictwa wyższego), (6) wpływ na wykluczenie grup społecznych ze względu na poziom zabezpieczenia materialnego. Wszystko to sprowadzić można do pojęcia logiki racjonalności ekonomicznej. Rządzący posługują się „mieszaną strategią”, która oparta jest na dwóch logikach postępowania – (1) logice władzy, (2) logice racjonalności ekonomicznej. Logika władzy to nic innego jak dążenie do zdobycia i utrzymania władzy, gdzie władza sama w sobie staje się celem, natomiast struktury państwa stanowią przestrzeń, którą należy przejąć lub opanować. Rządzący aby ukryć swoją bezideowość i konflikty w walce o przejęcie struktur państwa uprawiają politykę „na zewnątrz”, która przyjmuje formę „festiwalu” agonicznego dyskursu. Taka polityka możliwa jest dzięki rozdawnictwu podczas redystrybucji dóbr (niezgodnie z racjonalnością ekonomiczną) lub/i dzięki instrumentalnemu traktowaniu dystrybucji uznania. W związku z niemożnością utrzymania wysokiego poziomu rozdawnictwa, szczególnie w sytuacji kryzysu gospodarczego, rządzący chętnie posługują się logiką racjonalności ekonomicznej. Rozwiązania oparte na racjonalności ekonomicznej, mimo ich negatywnego odbioru przez społeczeństwo, wprowadzane są przy zastosowaniu argumentacji zagrożenia bezpieczeństwa (gospodarczego, socjalnego, narodowego itd.). Tym samym państwo wycofuje się z rządzenia na rzecz zarządzania niektórymi sferami państwa. Nie można tego nazwać inaczej jak „ucieczką” od odpowiedzialności, co jest szczególnie zauważalne w sytuacjach destabilizacji gospodarczej. W takich sytuacjach mamy do czynienia z „outsourcingiem zadań” państwa, co przyjmować może różne formy – (1) przenoszenie funkcji na inne instytucje przy zachowaniu kompetencji kontrolnych lub (2) przenoszenie obowiązków na inne własne instytucje, które wcześniej pełniły inną rolę. Wszystko to można nazwać rekonfiguracją funkcji państwa w związku z dominacją gospodarki kapitalistycznej i oddziaływaniem logiki racjonalności ekonomicznej. W tekście podjęto również problem dystrybucji dóbr i uznania, jednakże jedynie w aspekcie jej instrumentalizacji przez rządzących. Można wysunąć tezę, że liberalne koncepcje wolności jednostki oraz priorytet dla własności prowadzą do łatwiejszego ideologicznego uzasadnienia stosowania mieszanych strategii i racjonalności. W tekście przedstawiono też tezę o instrumentalizacji dystrybucji dóbr, tzn. instrumentalnego wykorzystywania dowartościowania różnych mniejszości w ramach systemu politycznego. Należy też stwierdzić, że dominacja logiki wolnego rynku prowadzi do deprecjacji redystrybucji dóbr w stosunku do gloryfikacji problematyki uznania. Tekst jest jedynie zarysowaniem problematyki wyczerpywania się formuły demokracji liberalnej, co przedstawiono na wybranych zagadnieniach. Podjęty problem demokracji liberalnej nie skupia się na próbie odtworzenia modelu tego rodzaju demokracji, raczej ważniejsze było stwierdzenie przejmowania w działaniu czegoś, co można określić mianem logiki racjonalności ekonomicznej. Wartą dalszego analizowania jest sama logika „mieszanej racjonalności”, którą sprowadzono do przenikania się „logiki władzy” i „logiki racjonalności ekonomicznej”.

Allergological evaluation of a dog population in a veterinary immuno-allergology consultation: What correlates in a canine model

Introduction: Allergic dermatitis (AD) is the most common canine pruritic condition in veterinary dermatology. Allergic dermatitis to flea bites presents the highest prevalence, followed by atopic dermatitis and food AD. This study aimed to identify possible correlation between data from clinical signs, intradermal tests (IDT) and specific IgE levels, which are used in dog AD assessment. Methods: Fifty five dogs from the Veterinary Hospital of the University of Évora (Portugal) and Rof Codina University Hospital (Lugo, Spain) outpatient consultations were studied by means of clinical inquiry, IDT and specific IgE determination. Thirty five of the patients belonged to predisposed breeds, 30 were females and 25 males. Forty one (74%) were indoor. Results: In 82% of cases first clinical signs appeared before the age of 3 years and 24% even before 1 year old. In 70% of the individuals clinical signs included itching, which was generalized in 66%, with 78% of paw licking and chewing. Clinical profile showed seasonal worsening in 64% of cases. From the 69.1% of dogs already presenting with dermatitis, 50% also presented external otitis and 28.9% self-inflicted alopecia. "Intense itching" was found in 10.5%, "medium itching" in 81.6% and “mild itching” in 5.26% of the patients. Prevalence of positive IDT was 37.3 % to Lep d, 29.41% to Der f, 27.5% to Der p, 25.5% to Dac g and 21.6% to Malassezia sp. From the 37 dogs submitted to food IDT, 40.5% revealed positive to beef, 27% to chicken, 27% to porc and 5.4% to lamb. Specific IgE > 150 EAU was found in 84% of dogs to indoor allergen sources and in 68% to pollens. A negative correlation was found between an outdoor life and the intensity (p = 0.033) and precocity (p = 0.026) of clinical signs. Sensitization to pollens was found positively correlated with the seasonality of clinical signs (p = 0.001) and the positivity for Dac g (p = 0.007). The prevalence of chronic otitis correlated positively with alopecia and reactivity to Lep d (p = 0.008), Plantago lanceolata (p = 0.026) and Platanus acerifolia (p = 0.017). There was no correlation between the results of ITD and specific IgE. Conclusion: We can conclude that correlation between different clinical signs and positive testing for some allergenic sources may occur, as well as between sensitization to pollens and the beginning, the intensity and the seasonality of dog patient clinical signs.