Rate coding
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Recent studies on the theoretical performance of latency and rate code in single neurons have revealed that the ultimate accuracy is affected in a nontrivial way by aspects such as the level of spontaneous activity of presynaptic neurons, amount of neuronal noise or the duration of the time window used to determine the firing rate. This study explores how the optimal decoding performance and the corresponding conditions change when the energy expenditure of a neuron in order to spike and maintain the resting membrane potential is accounted for. It is shown that a nonzero amount of spontaneous activity remains essential for both the latency and the rate coding. Moreover, the optimal level of spontaneous activity does not change so much with respect to the intensity of the applied stimulus. Furthermore, the efficiency of the temporal and the rate code converge to an identical finite value if the neuronal activity is observed for an unlimited period of time.
- MeSH
- časové faktory MeSH
- energetický metabolismus * MeSH
- lidé MeSH
- membránové potenciály MeSH
- modely neurologické * MeSH
- nervová síť cytologie fyziologie MeSH
- neuronové sítě * MeSH
- neurony fyziologie MeSH
- počítačová simulace MeSH
- výpočetní biologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
We define an optimal signal in parametric neuronal models on the basis of interspike interval data and rate coding schema. Under the classical approach the optimal signal is located where the frequency transfer function is steepest. Its position coincides with the inflection point of this curve. This concept is extended here by using Fisher information which is the inverse asymptotic variance of the best estimator and its dependence on the parameter value indicates accuracy of estimation. We compare the signal producing maximal Fisher information with the inflection point of the sigmoidal frequency transfer function.
Fast information transfer in neuronal systems rests on series of action potentials, the spike trains, conducted along axons. Methods that compare spike trains are crucial for characterizing different neuronal coding schemes. In this paper we review recent results on the notion of spiking randomness, and discuss its properties with respect to the rate and temporal coding schemes. This method is compared with other widely used characteristics of spiking activity, namely the variability of interspike intervals, and it is shown that randomness and variability provide two distinct views. We demonstrate that estimation of spiking randomness from simulated and experimental data is capable of capturing characteristics that would otherwise be difficult to obtain with conventional methods.
Early detection of colorectal cancer (CRC) is the key for prevention and the ability to impact long-term survival of CRC patients. Current CRC screening modalities are inadequate for global application because of low sensitivity and specificity in case of conventional stool-based screening tests, and high costs and a low participation compliance in colonoscopy. An accurate stool- or blood-based screening test with use of innovative biomarkers is an appealing alternative as it is non-invasive and poses minimal risk to patients. It is easy to perform, can be repeated at shorter intervals, and therefore would likely lead to a much higher compliance rates. Non-coding RNAs (ncRNAs) have recently gained attention because of their involvement in different biological processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis. An increasing number of studies have demonstrated that mutations or abnormal expression of ncRNAs are closely associated with various cancers, including CRC. The discovery that ncRNAs (mainly microRNAs) are stable in stool and in blood plasma and serum presents the opportunity to develop novel strategies taking advantage of circulating ncRNAs as early diagnostic biomarkers of CRC. This chapter is a comprehensive examination of aberrant ncRNAs expression levels in tumor tissue, stool and blood of CRC patients and a summary of the current findings on ncRNAs, including microRNAs, small nucleolar RNAs, small nuclear RNAs, Piwi-interacting RNAs, circular RNAs and long ncRNAs in regards to their potential usage for screening or early detection of CRC.
- MeSH
- adenokarcinom chemie diagnóza genetika MeSH
- adenom chemie diagnóza genetika MeSH
- časná detekce nádoru metody MeSH
- feces chemie MeSH
- kolorektální nádory chemie diagnóza genetika MeSH
- krevní plazma MeSH
- lidé MeSH
- nádorové biomarkery analýza krev MeSH
- nekódující RNA analýza krev MeSH
- pacientův souhlas se zdravotní péčí MeSH
- polypy tlustého střeva chemie diagnóza genetika MeSH
- regulace genové exprese u nádorů MeSH
- senzitivita a specificita MeSH
- sérum MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
BACKGROUND: Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor (GHSR), has two major functions: the stimulation of the growth hormone production and the stimulation of food intake. Accumulating evidence also indicates a role of ghrelin in cancer development. METHODS: We conducted a case-control study to examine the association of common genetic variants in the genes coding for ghrelin (GHRL) and its receptor (GHSR) with colorectal cancer risk. Pairwise tagging was used to select the 11 polymorphisms included in the study. The selected polymorphisms were genotyped in 680 cases and 593 controls from the Czech Republic. RESULTS: We found two SNPs associated with lower risk of colorectal cancer, namely SNPs rs27647 and rs35683. We replicated the two hits, in additional 569 cases and 726 controls from Germany. CONCLUSION: A joint analysis of the two populations indicated that the T allele of rs27647 SNP exerted a protective borderline effect (Ptrend = 0.004).
- MeSH
- alely MeSH
- dítě MeSH
- DNA nádorová genetika MeSH
- dospělí MeSH
- genetická predispozice k nemoci MeSH
- ghrelin genetika metabolismus MeSH
- incidence MeSH
- kolorektální nádory epidemiologie genetika metabolismus MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- polymorfismus genetický * MeSH
- receptory ghrelinu genetika metabolismus MeSH
- retrospektivní studie MeSH
- rizikové faktory MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- multicentrická studie MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
- Geografické názvy
- Česká republika MeSH
- Německo MeSH
Colorectal cancer (CRC) is one of the main causes of death of neoplasia. Demand for predictive and prognostic markers to reverse this trend is increasing. Long non-coding RNA HOTAIR (Homeobox Transcript Antisense Intergenic RNA) overexpression in tumors was previously associated with poor prognosis and higher mortality in different carcinomas. We analyzed HOTAIR expression levels in tumor and blood of incident sporadic CRC patients in relation to their overall survival with the aim to evaluate surrogate prognostic marker for CRC. Tissue donor group consisted of 73 CRC patients sampled for tumor and normal tissue. Blood donor group was represented by 84 CRC patients compared with 40 healthy controls. Patients were characterized for tumor-node-metastasis stage, tumor grade, microsatellite instability and tumor penetration by stromal cells. HOTAIR levels were assessed by real-time quantitative PCR. CRC patients had higher HOTAIR expression in blood than healthy controls (P = 0.0001), whereas there was no difference in HOTAIR levels between tumor and adjacent mucosa of CRC patients. HOTAIR levels positively correlated between blood and tumor (R = 0.43, P = 0.03). High HOTAIR levels in tumors were associated with higher mortality of patients [Cox's proportional hazard, hazard ratio = 4.4, 95% confidence interval: 1.0-19.2, P = 0.046]. The hazard ratio was even higher when blood HOTAIR levels were taken into account (hazard ratio = 5.9, 95% confidence interval: 1.3-26.1, P = 0.019). Upregulated HOTAIR relative expression in primary tumors and in blood of CRC patients is associated with unfavorable prognosis. Our data suggest that HOTAIR blood levels may serve as potential surrogate prognostic marker in sporadic CRC.
- MeSH
- dospělí MeSH
- kolon metabolismus MeSH
- kolorektální nádory krev genetika mortalita MeSH
- kvantitativní polymerázová řetězová reakce MeSH
- lidé středního věku MeSH
- lidé MeSH
- messenger RNA genetika MeSH
- míra přežití MeSH
- nádorové biomarkery krev genetika MeSH
- následné studie MeSH
- polymerázová řetězová reakce s reverzní transkripcí MeSH
- prognóza MeSH
- rektum metabolismus MeSH
- RNA dlouhá nekódující krev genetika MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- staging nádorů MeSH
- studie případů a kontrol MeSH
- stupeň nádoru MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
Článek popisuje hardware a software mikropočítačového systému určeného pro měření a vyhodnocování variability srdeční frekvence v medicínské praxi. System se skládá z nastavitelného hradního pásu s elektrodami, z vysilače a přijímače kódovaného radiového Signálu. Přijímač je připojen k osobnímu počítači IBM PC prostřednictvím standardního sériového portu (COMl nebo COM2). Součástí systému je softwarové vybavení pro vyhodnocení stavu autonomního nervového systému během speciálních testů jako Ewingova baterie kardiovaskulárních testů a tzv. „Short time" spektrální analýza variability srdeční frekvence. Popisovaný systém může být použit jak v běžné medicinské praxi, tak pro výzkumné účely především v kardiológii, diabetológii, neurologii a sportovním lékařství.
Hardware and software of a microcomputer system for measurement and evaluation of heart rate variability in medical practice is presented. The system involves an adjustable thorax belt with electrodes, a transmitter and a receiver of coded radio signals. The receiver is connected to a standard serial port (COMl or COM2) of IBM PC compatible personal computer. The system is completed by software programs allowing the determination of the autonomic nervous system state during special examinations, it means so-called Ewing's batery of cardiovascular tests and „Short Time" spectral analysis of heart rate variability. The described system -an be used both in daily medical practice and under conditions of experimental work. It can be applied especially in cardiology, diabetology, neurology and sport medicine.
The apparent stochastic nature of neuronal activity significantly affects the reliability of neuronal coding. To quantify the encountered fluctuations, both in neural data and simulations, the notions of variability and randomness of inter-spike intervals have been proposed and studied. In this article we focus on the concept of the instantaneous firing rate, which is also based on the spike timing. We use several classical statistical models of neuronal activity and we study the corresponding probability distributions of the instantaneous firing rate. To characterize the firing rate variability and randomness under different spiking regimes, we use different indices of statistical dispersion. We find that the relationship between the variability of interspike intervals and the instantaneous firing rate is not straightforward in general. Counter-intuitively, an increase in the randomness (based on entropy) of spike times may either decrease or increase the randomness of instantaneous firing rate, in dependence on the neuronal firing model. Finally, we apply our methods to experimental data, establishing that instantaneous rate analysis can indeed provide additional information about the spiking activity.
- Publikační typ
- časopisecké články MeSH
