Persistent dynamic attractors in activity patterns of cultured neuronal networks

Three remarkable features of the nervous system—complex spatiotemporal patterns, oscillations, and persistent activity—are fundamental to such diverse functions as stereotypical motor behavior, working memory, and awareness. Here we report that cultured cortical networks spontaneously generate a hierarchical structure of periodic activity with a strongly stereotyped population-wide spatiotemporal structure demonstrating all three fundamental properties in a recurring pattern. During these "superbursts," the firing sequence of the culture periodically converges to a dynamic attractor orbit. Precursors of oscillations and persistent activity have previously been reported as intrinsic properties of the neurons. However, complex spatiotemporal patterns that are coordinated in a large population of neurons and persist over several hours—and thus are capable of representing and preserving information—cannot be explained by known oscillatory properties of isolated neurons. Instead, the complexity of the observed spatiotemporal patterns implies large-scale self-organization of neurons interacting in a precise temporal order even in vitro, in cultures usually considered to have random connectivity

Értékpapírosítás: A bankok válasza a szabályozásra?

A cikk célja kétoldalú: egyrészről rövid áttekintést kíván adni az értékpapírosítási piac fejlődéséről és jelenéről, másrészről célja annak vizsgálata, hogy a szabályozási kötöttségek milyen módon hathatnak a bankok értékpapírosítási döntéseire

Chaotic Phase Synchronization in Bursting-neuron Models Driven by a Weak Periodic Force

We investigate the entrainment of a neuron model exhibiting a chaotic spiking-bursting behavior in response to a weak periodic force. This model exhibits two types of oscillations with different characteristic time scales, namely, long and short time scales. Several types of phase synchronization are observed, such as 1 : 1 phase locking between a single spike and one period of the force and 1 : l phase locking between the period of slow oscillation underlying bursts and l periods of the force. Moreover, spiking-bursting oscillations with chaotic firing patterns can be synchronized with the periodic force. Such a type of phase synchronization is detected from the position of a set of points on a unit circle, which is determined by the phase of the periodic force at each spiking time. We show that this detection method is effective for a system with multiple time scales. Owing to the existence of both the short and the long time scales, two characteristic phenomena are found around the transition point to chaotic phase synchronization. One phenomenon shows that the average time interval between successive phase slips exhibits a power-law scaling against the driving force strength and that the scaling exponent has an unsmooth dependence on the changes in the driving force strength. The other phenomenon shows that Kuramoto's order parameter before the transition exhibits stepwise behavior as a function of the driving force strength, contrary to the smooth transition in a model with a single time scale

Nukleáris medicina a prosztatarák diagnosztikájában és kezelésében (teranosztika) = Nuclear medicine in the diagnosis and treatment of prostate cancer (theranostics)

Az elmúlt években, évtizedekben a nukleáris medicina hatalmas fejlődésen ment át, számos radiofarmakológiai fejlesztés született, és a hibrid berendezésekkel (PET/CT, PET/MR, SPECT/ CT) végzett vizsgálatok is könnyebben elérhetővé váltak a klinikai gyakorlatban. A nukleáris onkológia egyik legjobban kutatott területe a prosztatarák volt, aminek köszönhetően több új radiofarmakon került forgalomba mind diagnosztikus, mind terápiás célra, ezeket Magyarországon is bevezették, illetve elérhető közelségbe kerültek. A szerzők azokat a – prosztatarák-diagnosztikában és -terápiában használt – nukleáris medicinai módszereket foglalták össze, amelyek a klinikai gyakorlatban a legfontosabbak. = In recent years and decades, nuclear medicine has undergone a huge development, many radiopharmacological developments have been made, and examinations with hybrid equipment (PET/CT, PET/MR, SPECT/CT) have become more easily available in clinical practice. One of the most researched areas of nuclear oncology was prostate cancer, as a result several novel radiopharmaceuticals were put on the market for both diagnostic and therapeutic purposes, and these were also introduced or became achievable in Hungary. The authors have summarized the nuclear medicine methods used in prostate cancer diagnosis and therapy, which are the most important in clinical practice

Increased mesiotemporal delta activity characterizes virtual navigation in humans

Hippocampal theta or rhythmic slow activity (RSA) occurring during exploratory behaviors and rapid-eye-movement (REM) sleep is a characteristic and well-identifiable oscillatory rhythm in animals. In contrast, controversy surrounds the existence and electrophysiological correlates of this activity in humans. Some argue that the human hippocampal theta occurs in short and phasic bursts. On the contrary, our earlier studies provide evidence that REM-dependent mesiotemporal RSA is continuous like in animals but instead of the theta it falls in the delta frequency range. Here we used a virtual navigation task in 24 epilepsy patients implanted with foramen ovale electrodes. EEG was analyzed for 1-Hz wide frequency bins up to 10 Hz according to four conditions: resting, non-learning route-following, acquisition and recall. We found progressively increasing spectral power in frequency bins up the 4 Hz across these conditions. No spectral power increase relative to resting was revealed within the traditional theta band and above in any of the navigation conditions. Thus the affected frequency bins were below the theta band and were similar to those characterizing REM sleep in our previous studies providing further indication that it is delta rather than theta that should be regarded as a human analogue of the animal RSA

A 19. századi magyar nemzetépítés elemeinek átértékelése új szempontok és új források alapján = Rethinking Nineteenth-century Nation-building in Hungary: New Perceptions, New Sources

Az OTKA támogatásával létrejött tudományos iskola a történettudomány nemzetközi fejlődése során előtérbe került új megközelítéseket alkalmazva elemezte a magyarországi nemzetépítés folyamatát néhány olyan konkrét részterületen, amelyek eddig a nemzeti problematika szempontjából háttérben maradtak a magyar történettudományban. A 19. századi tankönyvirodalom, az udvari kultúra és a színpadi szórakoztatás, a politikai röpiratok, a gazdaságtörténet, a demográfiai adatok, a divat, illetve a kollektív reprezentációk egyaránt vizsgálódásunk terepéül szolgáltak. A mai elméleti koncepciók szerint a nemzetet elsősorban diskurzusként gondoltuk el. Kutatásunk a modern nemzetet létrehozó diskurzusokat mint a korabeli társadalom eltérő nézeteinek és praxisainak különböző termékeit helyezte előtérbe. Ennek fényében nem kisebb történeti probléma vált láthatóvá, mint magának a nemzetépítés folyamatának a társadalmi beágyazottsága. Rámutattunk ugyanis arra az ellentmondásra, amely a nemzetről szóló homogenizáló diskurzusok és az őket létrehozó komplex társadalmi háttér között feszült. | The scientific school supported by OTKA, applying the most recent results of the international historical sciences, analyzed the process of the Hungarian nation-bulding on some concrete fields that have been partially neglicted by the Hungarian historiography so far. The history manuels, the royal court culture, the popular entertainment, the political pamphlets, the economic history, the fashion, the usage of demographic data and the collective representations were the main fields of our collective research. According to the most recent theoretical frameworks, we considered the nation primarily as a discourse. Our research approached the nation as the product of the various judgments and practices of the contemporary societies. Throughout that approach, a crucial historical problem, the social embeddedness of the nation-building process became visible. We tried to point out the contradiction between the homogenizing discourses about the nation and the complex social background that produced these discourses

Linear stability analysis of retrieval state in associative memory neural networks of spiking neurons

We study associative memory neural networks of the Hodgkin-Huxley type of spiking neurons in which multiple periodic spatio-temporal patterns of spike timing are memorized as limit-cycle-type attractors. In encoding the spatio-temporal patterns, we assume the spike-timing-dependent synaptic plasticity with the asymmetric time window. Analysis for periodic solution of retrieval state reveals that if the area of the negative part of the time window is equivalent to the positive part, then crosstalk among encoded patterns vanishes. Phase transition due to the loss of the stability of periodic solution is observed when we assume fast alpha-function for direct interaction among neurons. In order to evaluate the critical point of this phase transition, we employ Floquet theory in which the stability problem of the infinite number of spiking neurons interacting with alpha-function is reduced into the eigenvalue problem with the finite size of matrix. Numerical integration of the single-body dynamics yields the explicit value of the matrix, which enables us to determine the critical point of the phase transition with a high degree of precision.Comment: Accepted for publication in Phys. Rev.