Human brains use grids to represent space
Scientists partially funded by the European Union have for the first time identified a specific type of cell which acts like a spatial map in the human brain. Published in the journal Nature, the finding may help to explain how people create internal maps of new environments. The study, by a team from University College London, UK used brain imaging and virtual reality techniques to try to identify the cells. Called 'grid cells', these specialised neurons are thought to be involved in spatial memory and have previously been identified in rodent brains, but evidence of their presence in humans has not been documented until now. 'It is as if grid cells provide a cognitive map of space. In fact, these cells are very much like the longitude and latitude lines we're all familiar with on normal maps, but instead of using square grid lines, it seems the brain uses triangles,' said Dr Caswell Barry, one of the study authors. The research was partially funded by the SPACEBRAIN ('Space coding in hippocampo-entorhinal neuronal assemblies') project, funded under the 'Health' Theme of the Seventh Framework Programme (FP7). The project aims to understand how complex mental functions originate from electrical and chemical processes in brain cells. This means furthering the search for principles of microcircuit computation in the spatial representation system of rodents, using a combination of novel computational, electrophysiological, optical and molecular research tools that have never been applied before to the analysis of brain circuitry. Grid cells represent where an animal is located within its environment, which the researchers liken to having a satellite navigation system in the brain. They fire in patterns that show up as geometrically regular, triangular grids when plotted on a map of a navigated surface. They were discovered by a Norwegian lab in 2005 whose research suggested that rats create virtual grids to help them orient themselves in their surroundings and remember new locations in unfamiliar territory. During the course of the study, 42 participants were given a 'virtual reality task'. Researchers programmed a simple environment of a flat, grassy plain surrounded by circular cliff. Test subjects were then asked to collect and replace everyday objects within the environment, moving their viewpoint forward, right and left. Professor Neil Burgess, who led the team, added: 'The parts of the brain which show signs of grid cells - the hippocampal formation and associated brain areas - are already known to help us navigate our environment and are also critical for autobiographical memory. This means that grid cells may help us to find our way to the right memory as well as finding our way through our environment. These brain areas are also amongst the first to be affected by Alzheimer's disease, which may explain why getting lost is one of the most common early symptoms of this disease.'
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