Understanding Neural Maps with Topographica

The biological function of neurons can often be understood only in the context of large, highly interconnected networks. These networks typically form two-dimensional topographic maps, such as the retinotopic maps in mammalian visual cortex. Computational simulations of these areas have led to valuable insights about how cortical topography develops and functions, but further progress has been hindered due to the lack of appropriate simulation tools. This paper introduces the freely available Topographica maplevel simulator, originally developed at the University of Texas at Austin and now maintained at the University of Edinburgh, UK. Topographica is designed to make large-scale, detailed models practical. The goal is to allow neuroscientists and computational scientists to work together to understand how topographic maps and their connections organize and operate. This understanding will be crucial for integrating experimental observations into a comprehensive theory of brain function.

Pyrologia topographica id est De igne dissertatio juxta loca cum eorum descriptionibus Dominici Bottoni leontini ..

Mode of access: Internet.

Memoria topographica e historica sobre os Campos dos Goitacazes : com huma noticia breve de suas producções, e commercio ... /

Mode of access: Internet.

Memoria historica, chronologica, topographica e descriptiva da cidade de Paranagua e do seu municipio /

Mode of access: Internet.

De Romae veteris muris atque portis. Dissertatio topographica.

Mode of access: Internet.

Itinera mundi

Vorlage d. Digitalisats aus d. Besitz d. Theol. Hochschule St. Georgen

Lisbon, Portugal, 1871 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Carta topographica da cidade de Lisboa : reduzida da que foi levantada n secala de 1/1,000 em 1856 a 1858, sob a direc��o do general Filippe Folque, Director geral dos trabalhos geodesicos; Mesquita gr. It was published by Direc��o Geral dos Trabalhos Geodesicos do Reino in 1871. Scale 1:10,000. Covers Lisbon, Portugal. Map in Portuguese.The image inside the map neatline is georeferenced to the surface of the earth and fit to the European Datum 1950, UTM Zone 29N coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map.This map shows features such as roads, drainage, built-up areas and selected buildings, ground cover, and more. Relief shown by hachures. Includes index.This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.

Relacion descriptiva de la ciudad, y provincia de Truxillo del Peru : con noticias exactas de su estado politico ... /

Mode of access: Internet.

The history and antiquities of Hawsted, and Hardwick, in the county of Suffolk /

First ed. published in 1784 as no. 23 of Nichols' "Bibliotheca topographica britannica."

Elizabethan Oxford; reprints of rare tracts,

Includes index and bibliographical footnotes.

Neural Network Evidence for the Coupling of Presaccadic Visual Remapping to Predictive Eye Position Updating.

As we look around a scene, we perceive it as continuous and stable even though each saccadic eye movement changes the visual input to the retinas. How the brain achieves this perceptual stabilization is unknown, but a major hypothesis is that it relies on presaccadic remapping, a process in which neurons shift their visual sensitivity to a new location in the scene just before each saccade. This hypothesis is difficult to test in vivo because complete, selective inactivation of remapping is currently intractable. We tested it in silico with a hierarchical, sheet-based neural network model of the visual and oculomotor system. The model generated saccadic commands to move a video camera abruptly. Visual input from the camera and internal copies of the saccadic movement commands, or corollary discharge, converged at a map-level simulation of the frontal eye field (FEF), a primate brain area known to receive such inputs. FEF output was combined with eye position signals to yield a suitable coordinate frame for guiding arm movements of a robot. Our operational definition of perceptual stability was "useful stability," quantified as continuously accurate pointing to a visual object despite camera saccades. During training, the emergence of useful stability was correlated tightly with the emergence of presaccadic remapping in the FEF. Remapping depended on corollary discharge but its timing was synchronized to the updating of eye position. When coupled to predictive eye position signals, remapping served to stabilize the target representation for continuously accurate pointing. Graded inactivations of pathways in the model replicated, and helped to interpret, previous in vivo experiments. The results support the hypothesis that visual stability requires presaccadic remapping, provide explanations for the function and timing of remapping, and offer testable hypotheses for in vivo studies. We conclude that remapping allows for seamless coordinate frame transformations and quick actions despite visual afferent lags. With visual remapping in place for behavior, it may be exploited for perceptual continuity.