Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Ca2+ is a highly versatile intracellular signal that operates over a wide temporal range to regulate many different cellular processes. An extensive Ca2+-signalling toolkit is used to assemble signalling systems with very different spatial and temporal dynamics. Rapid highly localized Ca2+ spikes regulate fast responses, whereas slower responses are controlled by repetitive global Ca2+ transients or intracellular Ca2+ waves. Ca2+ has a direct role in controlling the expression patterns of its signalling systems that are constantly being remodelled in both health and disease.

/pdf/calcium-signalling-dynamics-homeostasis-and-remodelling-2oni038yeg.pdf

Calcium signalling: dynamics, homeostasis and remodelling

With few exceptions biological tissues strongly scatter light, making high-resolution deep imaging impossible for traditional⎯including confocal⎯fluorescence microscopy. Nonlinear optical microscopy, in particular two photon–excited fluorescence microscopy, has overcome this limitation, providing large depth penetration mainly because even multiply scattered signal photons can be assigned to their origin as the result of localized nonlinear signal generation. Two-photon microscopy thus allows cellular imaging several hundred microns deep in various organs of living animals. Here we review fundamental concepts of nonlinear microscopy and discuss conditions relevant for achieving large imaging depths in intact tissue.

/pdf/deep-tissue-two-photon-microscopy-2aqu6d6n65.pdf

Deep tissue two-photon microscopy

Thank you for reading principles of optics electromagnetic theory of propagation interference and diffraction of light. As you may know, people have search hundreds times for their favorite novels like this principles of optics electromagnetic theory of propagation interference and diffraction of light, but end up in harmful downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they are facing with some infectious bugs inside their computer.

Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Genetically encoded calcium indicators (GECIs) can be used to image activity in defined neuronal populations. However, current GECIs produce inferior signals compared to synthetic indicators and recording electrodes, precluding detection of low firing rates. We developed a single-wavelength GCaMP2-based GECI (GCaMP3), with increased baseline fluorescence (3-fold), increased dynamic range (3-fold) and higher affinity for calcium (1.3-fold). We detected GCaMP3 fluorescence changes triggered by single action potentials in pyramidal cell dendrites, with signal-to-noise ratio and photostability substantially better than those of GCaMP2, D3cpVenus and TN-XXL. In Caenorhabditis elegans chemosensory neurons and the Drosophila melanogaster antennal lobe, sensory stimulation-evoked fluorescence responses were significantly enhanced with GCaMP3 (4-6-fold). In somatosensory and motor cortical neurons in the intact mouse, GCaMP3 detected calcium transients with amplitudes linearly dependent on action potential number. Long-term imaging in the motor cortex of behaving mice revealed large fluorescence changes in imaged neurons over months.

/pdf/imaging-neural-activity-in-worms-flies-and-mice-with-3p3ty3yt7l.pdf

Imaging neural activity in worms, flies and mice with improved GCaMP calcium indicators

We studied the mosaics of six types of retinal neurons, asking how the position of a cell relates to the positions of other cells of that same type and also to cells of different types. Every neuron studied was found to be nonrandomly positioned: Cells of a particular type were evenly spaced. However, all cells were positioned randomly with respect to members of the other cell classes. This was true even when the cells were known to be synaptically connected. It is consistent with a concept of developmental pattern formation in which (i) the number of cells of a particular type and their laminar distribution are specified, and (ii) the final spatial position of each cell is controlled exclusively by a rule that prevents cells of the same type from being positioned close to each other. This sequence would imply that a cell's final position is independent of the cell's position at the time of its specification, and we suggest a reason why, in laminar structures containing many cell types, it might be desirable for this to be so.

https://www.pnas.org/content/pnas/97/5/2303.full.pdf

Spatial order within but not between types of retinal neurons.

Like most mammals, mice feature dichromatic color vision based on short (S) and middle (M) wavelength-sensitive cone types. It is thought that mammals share a retinal circuit that in dichromats compares S- and M-cone output to generate blue/green opponent signals, with bipolar cells (BCs) providing separate chromatic channels. Although S-cone-selective ON-BCs (type 9 in mouse) have been anatomically identified, little is known about their counterparts, the M-cone-selective OFF-BCs. Here, we characterized cone connectivity and light responses of selected mouse BC types using immunohistochemistry and electrophysiology. Our anatomical data indicate that four (types 2, 3a/b, and 4) of the five mouse OFF-BCs indiscriminately contact both cone types, whereas type 1 BCs avoid S-cones. Light responses showed that the chromatic tuning of the BCs strongly depended on their position along the dorsoventral axis because of the coexpression gradient of M- and S-opsin found in mice. In dorsal retina, where coexpression is low, most type 2 cells were green biased, with a fraction of cells (≈ 14%) displaying strongly blue-biased responses, likely reflecting S-cone input. Type 1 cells were also green biased but did not comprise blue-biased "outliers," consistent with type 1 BCs avoiding S-cones. We therefore suggest that type 1 represents the green OFF pathway in mouse. In addition, we confirmed that type 9 BCs display blue-ON responses. In ventral retina, all BC types studied here displayed similar blue-biased responses, suggesting that color vision is hampered in ventral retina. In conclusion, our data support an antagonistically organized blue/green circuit as the common basis for mammalian dichromatic color vision.

https://www.jneurosci.org/content/jneuro/31/17/6504.full.pdf

Chromatic Bipolar Cell Pathways in the Mouse Retina

We investigated the expression of Gγ13, a recently discovered G protein subunit, and a selection of Gβ subunits in retinal bipolar cells, by using a transgenic mouse strain in which green fluorescent protein is strongly expressed in a single type of cone bipolar cell. The cells have ON morphology, and patch-clamp recordings in slices confirmed that they are of the physiological ON type. Immunohistochemistry showed that Gγ13 is expressed in rod bipolar cells and ON cone bipolar cells, where it is colocalized in the dendrites with Gαo. ON and OFF cone bipolar cells and rod bipolar cells were identified among dissociated cells by their green fluorescence and/or distinct morphology. Hybridization of single-cell polymerase chain reaction products with cDNA probes for G protein subunits Gβ1 to 5 showed that Gβ3, Gβ4, and Gγ13 are coexpressed in ON bipolar cells but not present in OFF bipolar cells. Gβ1, 2, and 5 are expressed in partially overlapping subpopulations of cone bipolar cells. Gγ13 and Gβ3 and/or Gβ4, thus, seem selectively to participate in signal transduction by ON bipolar cells. J. Comp. Neurol. 455:1–10, 2003. © 2002 Wiley-Liss, Inc.

Thomas Euler

Papers

Spatial order within but not between types of retinal neurons.

Chromatic Bipolar Cell Pathways in the Mouse Retina

G protein subunit Gγ13 is coexpressed with Gαo, Gβ3, and Gβ4 in retinal ON bipolar cells

Die Retina im Rausch der Kanäle

Chromatic Coding from Cone-type Unselective Circuits in the Mouse Retina