128 research outputs found
Spike Timing-Dependent Plasticity in the CA1 Pyramidal Neuron in a Modeled Hippocampal Circuit
Spike timing-dependent plasticity (STDP) plays an important role in sculpting informationstoring circuits in the hippocampus, since motor learning and memory are thought to be
closely linked with this classical plasticity. To further understand the information delivery in
a hippocampus circuit, we build a computational model to study the potential role of linear
changes in the synaptic weight and synaptic number. Several key results have been obtained:
(i) Changes in the synaptic weight and numbers lead to different long-term modification; (ii)
the first paired spiking from two neurons significantly influences the adjusted subsequent
paired spiking; the pre-post spiking pair strengthens the following paired spiking; however,
the post-pre spiking pair depresses the subsequent spiking; (iii) when the synaptic weight and
synaptic numbers are changed, the interval of the first spiking pair may undergo reduction,
and (iv) when we stimulate a stellate neuron weakly or decrease the capacitance of CA1
pyramidal neuron, LTP is more easily produced than LTD; on the contrary, LTD is more easily
produced in an opposite situation; increase in the synaptic numbers can promote activation of
the CA1 pyramidal neuron.Пластичність, залежна від часу генерування піків (spike
timing-dependent plasticity – STDP), відіграє важливу роль
у формуванні нейромереж, що накопичують інформацію
в гіпокампі; вважається, що моторне навчання та пам’ять
тісно пов’язані з пластичністю цього типу. Для глибшого
розуміння процесів передачі інформації в гіпокампальній
нейромережі ми створили комп’ютерну модель, щоб
вивчити потенціальну роль лінійних змін синаптичної ваги
та числа синапсів у таких мережах. Було отримано чотири
основні результати: 1) зміни ваги та числа синапсів можуть
призводити до появи різних феноменів довготривалої
модифікації; 2) перша пара потенціалів дії, генерована
двома нейронами, істотно впливає на характеристики другої
пари піків; генерація пари піків у пре-пост-послідовності
полегшує генерацію наступної пари, тоді як пост-прегенерація пари пригнічує генерацію наступної пари; 3) коли
вага синапсів та їх кількість змінюються, інтервал у першій
парі піків зменшується; 4) коли стимулювати зірчастий
нейрон з невеликою інтенсивністю або зменшити ємність
пірамідного нейрона CA1, легше індукується довготривала
потенціація; у протилежній ситуації легше виникає
довготривала депресія; збільшення числа синапсів полегшує
активацію пірамідного нейрона CA1
Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV
By analyzing the data sets of 17.3 pb taken at GeV
and 6.5 pb taken at GeV with the BESII detector at the
BEPC collider, we have measured the observed cross sections for 12 exclusive
light hadron final states produced in annihilation at the two energy
points. We have also set the upper limits on the observed cross sections and
the branching fractions for decay to these final states at 90%
C.L.Comment: 8 pages, 5 figur
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar
The branching ratios and Angular distributions for J/psi decays to Lambda
Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons
The branching fractions for the inclusive Cabibbo-favored ~K*0 and
Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample
of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with
the BES-II detector at the BEPC collider. The branching fractions for the
decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 ->
\~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and
BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching
fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X)
< 6.6%
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