1,807,440 research outputs found
Empress I of the Royal Court of the Golden Spike Empire Deanna : The Origin of the Spike
No full textBlack and white Photograph of Henry Bender "Deanna" Empress I " The Origin of the Spike
History of The Royal Court of the Golden Spike Empire up to 2013
No full textText document Page 23 of the 2013 Royal Court of the Golden Spike Empire Coronation Program. a brief historical overview of the Royal Court of the Golden Spike Empire, Utah Oldest LGBT Organization June 1976- Present. with photo Illustration of Pepper Prespentt Emperor I the first lesbian to hold a title in the International Imperial Court System. Originally Imperial Court of Utah it broke up during the 4th reign (1979-1980) after the court resigned, and became the Royal Court of the Golden Spike Empire through the support of remaining membersConverted from .png to .pdf for compatibilit
2013 The Royal Court of the Golden Spike Empire Community Service Award Announcement
No full textText document page 22 of the 2013 Royal Court of the Golden Spike Empire coronation program. Community Service award announcement for the 2013 year, Sheneka Christy Empress 20 & 32Converted from .png to .pdf for compatibility; pages combined into one documen
A universal model for spike-frequency adaptation
No full textSpike-frequency adaptation is a prominent feature of neural dynamics. Among other mechanisms, various ionic currents modulating spike generation cause this type of neural adaptation. Prominent examples are voltage-gated potassium currents (M-type currents), the interplay of calcium currents and intracellular calcium dynamics with calcium-gated potassium channels (AHP-type currents), and the slow recovery from inactivation of the fast sodium current. While recent modeling studies have focused on the effects of specific adaptation currents, we derive a universal model for the firing-frequency dynamics of an adapting neuron that is independent of the specific adaptation process and spike generator. The model is completely defined by the neuron's onset f-I curve, the steady-state f-I curve, and the time constant of adaptation. For a specific neuron, these parameters can be easily determined from electrophysiological measurements without any pharmacological manipulations. At the same time, the simplicity of the model allows one to analyze mathematically how adaptation influences signal processing on the single-neuron level. In particular, we elucidate the specific nature of high-pass filter properties caused by spike-frequency adaptation. The model is limited to firing frequencies higher than the reciprocal adaptation time constant and to moderate fluctuations of the adaptation and the input current. As an extension of the model, we introduce a framework for combining an arbitrary spike generator with a generalized adaptation current
On the stationary Cahn-Hilliard equation: Interior spike solutions
No full textWe study solutions of the stationary Cahn-Hilliard equation in a bounded smooth domain which have a spike in the interior. We show that a large class of interior points (the "nondegenerate peak" points) have the following property: there exist such solutions whose spike lies close to a given nondegenerate peak point. Our construction uses among others the methods of viscosity solution, weak convergence of measures and Liapunov-Schmidt reduction
Design Optimisation of Front-End Neural Interfaces for Spike Sorting Systems
No full text09.04.13 KB. Accepted version ok to add to spiral. IEEE policyThis work investigates the impact of the analogue
front-end design (pre-amplifier, filter and converter) on spike sorting performance in neural interfaces. By examining key design parameters including the signal-to-noise ratio, bandwidth,
filter type/order, data converter resolution and sampling rate, their sensitivity to spike sorting accuracy is assessed. This is applied to commonly used spike sorting methods such as template matching, 2nd derivative-features, and principle component analysis. The results reveal a near optimum set of parameters to increase performance given the hardware-constraints. Finally, the relative costs of these design parameters on resource efficiency (silicon area and power requirements) are quantified through reviewing the state-of-the-art
Membrane potential fluctuations determine the precision of spike timing and synchronous activity: a model study
No full textKretzberg J, Egelhaaf M, Warzecha A-K. Membrane potential fluctuations determine the precision of spike timing and synchronous activity: a model study. Journal of computational neuroscience. 2001;10(1):79-97.It is much debated on what time scale information is encoded by neuronal spike activity. With a phenomenological model that transforms time-dependent membrane potential fluctuations into spike trains, we investigate constraints for the timing of spikes and for synchronous activity of neurons with common input. The model of spike generation has a variable threshold that depends on the time elapsed since the previous action potential and on the preceding membrane potential changes. To ensure that the model operates in a biologically meaningful range, the model was adjusted to fit the responses of a fly visual interneuron to motion stimuli. The dependence of spike timing on the membrane potential dynamics was analyzed. Fast membrane potential fluctuations are needed to trigger spikes with a high temporal precision. Slow fluctuations lead to spike activity with a rate about proportional to the membrane potential. Thus, for a given level of stochastic input, the frequency range of membrane potential fluctuations induced by a stimulus determines whether a neuron can use a rate code or a temporal code. The relationship between the steepness of membrane potential fluctuations and the timing of spikes has also implications for synchronous activity in neurons with common input. Fast membrane potential changes must be shared by the neurons to produce synchronous activity
Characteristics of night-time absorption spike events
No full textInternational audienceSudden increases in cosmic radio noise absorption, known as spike events, have been identified as signatures of substorms in the previous studies. Using data from the IRIS (Imaging Riometer for Ionospheric Studies) at Kilpisjärvi, Finland (L~6) more than 450 night-time spike events between 1994 and 2003 have been identified. Spike events fall into four distinct categories based on their structure and the background magnetic activity as indicated by a local westward electrojet (IL index) derived from the IMAGE (International Monitor for Auroral Geomagnetic Effects) magnetometer network as well as Pi2 magnetic pulsations from SAMNET (The UK Sub-Auroral Magnetometer Network). Classifying the types of absorption spikes allows for identification of phenomena such as multiple onsets and pseudobreakups from riometer data. In addition we have studied the statistical variation of absorption spikes and their sub-classes. This includes examining the magnetic local time (MLT) distribution and the seasonal and solar-cycle variation in spike occurrence. Those that seem to represent substorm onsets show a decidedly different MLT variation to those isolated spikes that represent pseudobreakups. The occurrence of spikes during different levels of geomagnetic activity is examined using the Kp index. Wavelet analysis has been used for studying the temporal structure of spikes; also the direction of motion of spike events and localisation of spikes are presented for all events and each sub-class and results are compared with previous studies. Statistical studies are supported with X-ray images of aurora from PIXIE (The Polar Ionospheric X-ray Imaging Experiment) when available
Spike-triggered averages (STAs) for spike tuples.
No full textSTAs for spike tuples with a silence time of 20 ms and inter-spike interval (ISI) up to 20 ms (aligned on first spike in a tuple). Left column shows lAIS values averaged over cell pairs for ISI of 1 ms to 10 ms, right column shows averaged lTE values (shaded areas indicate ±1SD). The lTE values are shifted by the individual delay between RGC and LGN cell for each pair such that a spike at index t = 0 indicates a transferred spike with a delay corresponding to the reconstructed information transfer delay. The predictability of the second RGC spike in a tuple, measured by the lAIS, was high for ISI from 3 ms to 7 ms, while first spikes in a tuple were unpredictable as indicated by no or negative lAIS. Information transfer measured by lTE was high for all RGC spikes with highest values for the second spike in a tuple.</p
Detecting rate changes in spike trains
No full textNeurone sind elementare Bausteine des Gehirns, welche Informationen über Aktionspotentiale (spikes) austauschen bzw. kodieren. In der statistischen Analyse von spike trains werden diese als Realisierung von stochastischen Punktprozessen betrachtet, oftmals unter der Annahme von stationären Feuerraten. Allerdings können diese Modellannahmen zu Fehlinterpretationen führen. Das Ziel dieser Arbeit war es, die Stationaritätsannahme zu prüfen und einen statistischen Test zu entwickeln, um Ratenveränderungen zu lokalisieren. Unter der Annahme, dass der spike train ein nichtstationärer Poisson Prozess mit stückweise konstanter Feuerrate ist, wurde ein Stufen-Filter-Test entwickelt, welcher die Zeitpunkte der Ratenänderung schätzt. Der Test operiert auf unterschiedlichen Zeitskalen und wird somit der großen Variation an Feuerraten in experimentellen spike trains gerecht. Zusätzlich wurde eine grafische Darstellung zur Veränderung der Feuerrate vorgeschlagen. Die Anwendung auf realen Daten ergab, dass die Methode plausible Ratenwechsel findet und somit das Schätzen der Ratenfunktion gemäß einer Stufenfunktion ermöglicht.Neuronal activity in the brain is often investigated in the presence of stimuli, termed externally driven activity. This stimulus-response-perspective has long been focussed on in order to find out how the nervous system responds to different stimuli. The neuronal response consists of baseline activity, so called spontaneous activity1, and activity which is caused by the stimulus. The baseline activity is often considered as constant over time which allows the identification of the stimulus-evoked part of the neuronal response by averaging over a set of trials.
However, during the last years it has been recognized that own dynamics of the nervous system plays an important role in information processing. As a consequence, spontaneous activity is no longer regarded only as background ’noise’ and its role in cortical processing is reconsidered. Therefore, the study of spontaneous firing pattern gains more importance as these patterns may shape neuronal responses to a larger extent as previously thought. For example, recent findings suggest that prestimulus activity can predict a person’s visual perception performance on a single trial basis (Hanslmayr et al., 2007). In this context, Ringach (2009) remarks that one can learn much about even the quiescent state of the brain which “underlies the importance of understanding cortical responses as the fusion of ongoing activity and sensory input”.
Taking into account that spontaneous activity reflects anything else but noise, new challenges arise when analysing neuronal data. In this thesis one of these problems related to the analysis of neuronal activity will be adressed, namely the nonstationarity of firing rates.
The present work consists of four chapters. First of all the introduction gives neurophysiological background information to get an idea of neuronal information processing. Afterwords the theory of point processes is provided which forms the basis for modeling neuronal spiking data. In the last section of the introduction a statement of the problem is given. Chapter 2 proposes an easily applicable statistical method for the detection of nonstationarity. It is applied to simulations and to real data in order to show its capabilities. Thereafter, four other approaches are presented which provide useful illustrations concerning the nonstationarity of the firing rate but share the problem that one cannot make objective statements on the basis of their results. They were developed in the course of establishing a suitable method. In chapter 4 the results are discussed and suggestions for further study are given
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