Coincidence detection

Initial evidence linking Hebb s coincidence detection rule to learning and memory 865... 

Molecular mechanisms underlying the early- and late-phase expressions of LTP. While opening the NMDA receptors is crucial for coincidence-detection, the sensitivity and robustness of coincidence-detection is not solely determined by the opening time-window. It is dependent on at least three other features summation of the opening duration, the peak amplitude and proper intracellular signal transduction. 

Initial evidence linking Hebb s coincidence detection rule to learning and memory. As the unique receptor in the brain with the coincidence-detection property, the NMDA receptor is an ideal candidate to gate the formation of memory at the synaptic level. Early observations demonstrated that infusion of NMDA receptor blockers into brain ventricles resulted in animals poor performance in the hidden-platform water maze. At first, this seemed to provide evidence for the role of hippocampal LTP in memory formation. Unfortunately, careful analyses revealed that poor performances in the water maze tests... 

While the conditional gene knockout experiments are supportive of a role for the NMDA receptors in memory, they are less than fully conclusive in linking the synaptic coincidence-detection feature of the NMDA receptor to memory formation. Like all loss-of-function studies, CA1-specific gene-knockout experiments could, in theory, produce memory impairment via a mechanism independent of the coincidence-detection function of the NMDA receptor. For example, one may argue that the physical absence of the NMDA receptor channels may cause subtle structural reconfiguration at the synapse, thereby altering normal synaptic transmission. Therefore, the memory impairment in CA1-specific NR1 knockout mice does not allow a firm conclusion that the coincidence-detection function of NMDA receptors controls learning and memory processes at the cellular level. 

Kabakov AY, Karkanias NB, Lenox RH, et al Synapse-specific accumulation of lithium in intracellular microdomains a model for uncoupling coincidence detection in the brain. Synapse 28 271-279, 1998... 

Caterina, M. J., M. A. Schumacher, M. Tominaga, T. A. Rosen, J. D. Levine and D. Julius, 1997, The capsaicin receptor a heat-activated ion channel in the pain pathway, Nature, 389, (6653), pp. 816-824 Chuang, H. H., W. M. Neuhausser and D. Julius, 2004, The Super-Cooling Agent Icilin Reveals a Mechanism of Coincidence Detection by a Temperature-Sensitive TRP Channel, Neuron, 43, (6), pp. 859-869... 

At first sight, it seems surprising to observe competitive reactions within the same complex. However, it must be noticed that in the ionization processes the internal energy distribution within the ions can be broad since the cluster s geometries in the Sj excited state and the ionic state can be very different. This can be seen by the ionization threshold measurements which do not exhibit clear onsets. Therefore, the presence of competitive processes can be explained by different barrier heights for the different channels. When the ions are prepared below one barrier and above the other one, only one product will be observed. Due to this broad internal energy distribution, on average, many channels can be detected. Coincidence detection of the zero kinetic electron and the product ions... 

Llinas, R.R., Leznik, E.,and Urbano, F.J. Temporal binding via cortical coincidence detection of specific and nonspecific thalamocortical inputs a voltage-dependent dye-imaging study in mouse brain slices. Proc Natl Acad Sci USA 2002,99 449-454. 

Coincidence detection of the fragment ions produced from a specific explosion pathway is achieved by collecting the events in which all of the frag-... 

The purpose of the detector surrounding the antihydrogen trap is to discriminate between signals due to the annihilation of antihydrogen and those due to the trapped clouds of antiprotons and positrons. For this, one needs to provide temporal and spatial coincident detection of the annihilation of an antiproton and a positron. It should also allow reconstruction of the annihilation vertex with sufficient resolution to discriminate between annihilations on the wall of the charged particle traps and those resulting from possible collisions with residual gas atoms. In addition it must have a sufficiently high rate capability to allow the study of the time evolution of the recombination process. 

Carlton JG, Cullen PJ. Coincidence detection in phosphoinositide signaling. Trends Cell Biol. 2005 15 540-547. 

AEc is the effective coincidence energy resolution and the effective coincidence detection efficiency. 

The scheme we have described allows the output photons to travel freely in space, so that they may further be used in quantum communication protocols, and this is achieved by detecting one and only one photon in modes 63 and 64. The fact that we do not yet have single-photon detectors for this wavelength at our disposal actually forces us to implement a four-fold coincidence detection to confirm that photons actually arrive in the output modes 61 and 62. 

Positron emission tomography (PET) is based on the principle of coincidence detection of the two 511-keV photons arising from positron emitters, which will be discussed in detail later. 

The 511-keV annihilation photons originating from different locations in the body are attenuated by the tissue, as they traverse different thicknesses to reach the detector pair in coincidence. If /z is the linear attenuation coefficient of 511-keV photons in the tissue, and a and b are the tissue thicknesses traversed by the two 511-keV photons along the LOR (Fig. 3.7), then the probability P of a coincidence detection is given by... 

---