Emergence of beta/gamma oscillations: ING, PING, and what about RING?

Poster presentation from Twentieth Annual Computational Neuroscience Meeting: CNS*2011 Stockholm, Sweden. 23-28 July 2011. Background: Oscillatory activity in high-beta and gamma bands (20-80Hz) is known to play an important role in cortical processing being linked to cognitive processes and behavior. Beta/gamma oscillations are thought to emerge in local cortical circuits via two mechanisms: the interaction between excitatory principal cells and inhibitory interneurons – the pyramidal-interneuron gamma (PING) [1], and in networks of coupled inhibitory interneurons under tonic excitation – the interneuronal gamma (ING) [2]. Experimental evidence underlines the important role of inhibitory interneurons and especially of the fast spiking (FS) interneurons [3,4]. We show in simulation that an important property of FS neurons, namely the membrane resonance (frequency preference), represents an additional mechanism – the resonance induced gamma (RING), i.e. modulation of oscillatory discharge by resonance. RING promotes frequency stability and enables oscillations in purely excitatory networks. Methods: Local circuits were modeled with small world networks of 80% excitatory and 20% inhibitory neuron populations interconnected in small-world topology by realistic conductance-based synapses. Neuron populations were leaky integrate and fire (LIF) or Izhikevich resonator (RES) neurons. We also tested networks of purely inhibitory and purely excitatory RES neurons. Networks were stimulated with miniature postsynaptic potentials (MINIs) [5] and with low frequency sinusoidal (0.5 Hz) input that mimics the effect of gratings passing trough the visual field. The activity was calibrated to match recordings from cat visual cortex (firing rate, oscillatory activity). Results: Sinusoidal input modulates network oscillation frequency. This effect is most prominent in IF excitatory and IF inhibitory (IF-IF) networks and less prominent (about 4 times) in IF-RES or RES-IF networks where frequency remains relatively stable. The most stable frequency was observed in networks of pure resonators (RES-RES, None-RES, RES-None). Interestingly, purely excitatory RES networks (RES-None) were also able to exhibit oscillations through RING. By contrast purely excitatory or inhibitory IF networks (IF-None, None-IF) were not able to express oscillations under these conditions, matching experimental parameters. Conclusions: In both PING and ING, adding membrane resonance to principal cells or inhibitory interneurons stabilizes network oscillation frequency via the RING mechanism. Notably, in networks of purely excitatory networks, where ING and PING are not defined, oscillations can emerge via the RING mechanism if membrane resonance is expressed. Thus, RING appears as a potentially important mechanism for promoting stable network oscillations

Traces of the Second Demographic Transition in Four Selected Countries in Central and Eastern Europe: Union Formation as a Demographic Manifestation

Using data from the first round of the national Gender and Generations Surveys of Russia, Romania, and Bulgaria, and from a similar survey of Hungary, which were all collected in recent years, we study rates of entry into marital and non-marital unions. We have used elements from the narrative of the Second Demographic Transition (SDT) as a vehicle to give our analysis of the data from the four countries some coherence, and find what can be traces of the SDT in these countries. The details vary by country; in particular, latter-day developments in union formation patterns did not start at the same time in all the countries, but in our assessment it began everywhere before communism fell, that is, before the societal transition to a market economy got underway in 1990

Spectrum and compactness of the Cesàro operator on weighted l_p spaces

[EN] An investigation is made of the continuity, the compactness and the spectrum of the Ces`aro operator C when acting on the weighted Banach sequence spaces l_p(w), 1 < p < 1, for a positive decreasing weight w, thereby extending known results for C when acting on the classical spaces l_p. New features arise in the weighted setting (for example, existence of eigenvalues, compactness) which are not present in l_p.The research of the first two authors was partially supported by the projects MTM2013-43540-P and GVA Prometeo II/2013/013 (Spain).Albanese, A.; Bonet Solves, JA.; Ricker, WJ. (2015). Spectrum and compactness of the Cesàro operator on weighted l_p spaces. Journal of the Australian Mathematical Society. 99(3):287-314. https://doi.org/10.1017/S1446788715000221S28731499

Protective effects of quercetin from oxidative/nitrosative stress under intermittent hypobaric hypoxia exposure in the rat’s heart

Background Exposure to high altitude in hypobaric hypoxia (HH) is considered to be a physiological oxidative/nitrosative stress. Quercetin (Que) is an effective antioxidant and free radical scavenger against oxidative/nitrosative stress. Aims The aim of this study was to investigate the cardioprotective effects of Que in animals exposed to intermittent HH (IHH) and therefore exposed to oxidative/nitrosative stress. Materials and methods Wistar albino male rats were exposed to short-term (2 days) or long-term (4 weeks; 5 days/week) IHH in a hypobaric chamber (5,500 m, 8 h/day, 380 mmHg, 12% O2, and 88% N2). Half of the animals received natural antioxidant Que (body weight: 30 mg/kg) daily before each IHH exposure and the remaining rats received vehicle (carboxymethylcellulose solution). Control rats were kept under normobaric normoxia (Nx) and treated in a corresponding manner. One day after the last exposure to IHH, we measured the cardiac hypoxia-induced oxidative/nitrosative stress biomarkers: the malondialdehyde (MDA) level and protein carbonyl (PC) content, the activity of some antioxidant enzymes [superoxide dismutase (SOD) and catalase (CAT)], the nitrite plus nitrate (NOx) production, and the inducible nitric oxide synthase (iNOS) protein expression. Results Heart tissue MDA and PC levels, NOx level, and iNOS expression of IHH-exposed rats had increased, and SOD and CAT activities had decreased compared with those of the Nx-exposed rats (control groups). MDA, CP, NOx, and iNOS levels had decreased in Que-treated IHH-exposed rats compared with IHH-exposed rats (control groups). However, Que administration increased SOD and CAT activities of the heart tissue in the IHH-exposed rats. Conclusion HH exposure increases oxidative/nitrosative stress in heart tissue and Que is an effective cardioprotective agent, which further supports the oxidative cardiac dysfunction induced by hypoxia

Damage control surgery in abdominal traumatology. Three cases report

Clinica Chirurgie II, Spitalul Clinic Judeţean de Urgenţă MureşScopul principal al studiului clinic este de a accentua importanța chirurgiei de control lezional în traumele majore abdominale. Cu toate că nu am realizat un studiu retrospectiv al experienţei noastre în domeniu, am considerat util să prezentăm trei situaţii clinice în care pentru leziuni diferite chirurgia de control lezional a fost urmată de rezultate favorabile, atrăgând atenția asupra indicațiilor, criteriilor clinice, paraclinice și operatorii care determină utilizarea metodei.The main purpose of this clinical study is to emphasize the importance of the damage control surgery in major abdominal trauma. Although we do not made a statistical retrospective analysis of our experience in this issue, we describe here three of our cases where we performed damage control surgery with good postoperative results, drawing attention upon indications, clinical, paraclinical and operative criteria which indicate the method

Visual Exploration and Object Recognition by Lattice Deformation

Mechanisms of explicit object recognition are often difficult to investigate and require stimuli with controlled features whose expression can be manipulated in a precise quantitative fashion. Here, we developed a novel method (called “Dots”), for generating visual stimuli, which is based on the progressive deformation of a regular lattice of dots, driven by local contour information from images of objects. By applying progressively larger deformation to the lattice, the latter conveys progressively more information about the target object. Stimuli generated with the presented method enable a precise control of object-related information content while preserving low-level image statistics, globally, and affecting them only little, locally. We show that such stimuli are useful for investigating object recognition under a naturalistic setting – free visual exploration – enabling a clear dissociation between object detection and explicit recognition. Using the introduced stimuli, we show that top-down modulation induced by previous exposure to target objects can greatly influence perceptual decisions, lowering perceptual thresholds not only for object recognition but also for object detection (visual hysteresis). Visual hysteresis is target-specific, its expression and magnitude depending on the identity of individual objects. Relying on the particular features of dot stimuli and on eye-tracking measurements, we further demonstrate that top-down processes guide visual exploration, controlling how visual information is integrated by successive fixations. Prior knowledge about objects can guide saccades/fixations to sample locations that are supposed to be highly informative, even when the actual information is missing from those locations in the stimulus. The duration of individual fixations is modulated by the novelty and difficulty of the stimulus, likely reflecting cognitive demand

Mean ergodicity and spectrum of the Cesàro operator on weighted c0 spaces

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