Understanding the retinal basis of vision across species

The vertebrate retina first evolved some 500 million years ago in ancestral marine chordates. Since then, the eyes of different species have been tuned to best support their unique visuoecological lifestyles. Visual specializations in eye designs, large-scale inhomogeneities across the retinal surface and local circuit motifs mean that all species' retinas are unique. Computational theories, such as the efficient coding hypothesis, have come a long way towards an explanation of the basic features of retinal organization and function; however, they cannot explain the full extent of retinal diversity within and across species. To build a truly general understanding of vertebrate vision and the retina's computational purpose, it is therefore important to more quantitatively relate different species' retinal functions to their specific natural environments and behavioural requirements. Ultimately, the goal of such efforts should be to build up to a more general theory of vision

Modelling and application of a cross-aperture coupled single feed circulary polarised patch antenna

Available from British Library Document Supply Centre-DSC:DXN046548 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Modelling and application of a cross-aperture coupled single feed circularly polarised patch antenna

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN019090 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Retinal horizontal cells use different synaptic sites for global feedforward and local feedback signaling

In the outer plexiform layer (OPL) of the mammalian retina, cone photoreceptors (cones) provide input to more than a dozen types of cone bipolar cells (CBCs). In the mouse, this transmission is modulated by a single horizontal cell (HC) type. HCs perform global signaling within their laterally coupled network but also provide local, cone-specific feedback. However, it is unknown how HCs provide local feedback to cones at the same time as global forward signaling to CBCs and where the underlying synapses are located. To assess how HCs simultaneously perform different modes of signaling, we reconstructed the dendritic trees of five HCs as well as cone axon terminals and CBC dendrites in a serial block-face electron microscopy volume and analyzed their connectivity. In addition to the fine HC dendritic tips invaginating cone axon terminals, we also identified “bulbs,” short segments of increased dendritic diameter on the primary dendrites of HCs. These bulbs are in an OPL stratum well below the cone axon terminal base and make contacts with other HCs and CBCs. Our results from immunolabeling, electron microscopy, and glutamate imaging suggest that HC bulbs represent GABAergic synapses that do not receive any direct photoreceptor input. Together, our data suggest the existence of two synaptic strata in the mouse OPL, spatially separating cone-specific feedback and feedforward signaling to CBCs. A biophysical model of a HC dendritic branch and voltage imaging support the hypothesis that this spatial arrangement of synaptic contacts allows for simultaneous local feedback and global feedforward signaling by HCs

INTERNET, GUERRA Y PAZ EN COLOMBIA: CONFLICTO, NARRATIVAS E IDENTIDADES

El texto presenta una síntesis del componente tecnológico de la investigación interinstitucional “Internet, guerra y paz en Colombia”. Para tal fin, se hace un seguimiento a las nociones de innovación tecnológica, su uso y la construcción de la paz. En primer lugar, se reconstruye la discusión en torno a Internet en tanto objeto de estudio; posteriormente, se hace énfasis en el uso como apropiación comunicativa del medio y, finalmente, se realizan algunas anotaciones en términos de la transformación de los espacios comunicativos públicos en relación con el conflicto armado