We orient ourselves and navigate our way through our environment using a process called spatial navigation, by which we can identify our current location and plan our movements. This process is based on out ability to map our environment and identify and remember landmarks.
This process involves the creation of a 'cognitive map' that allows potential routes and optimal paths to a new position in our environment to be identified.
Recently the neurones responsible for spatial navigation and the cognitive map have been found within the entorhinal cortex of the temporal lobe of experimental animals .
The entorhinal cortex is intimately involved in navigating ourelves through our environment, and in selecting appropriate routes to a desired place.
Experimental setup for recording spatially responsive neurons. The plot at the top right shows the final data form, in which the activity of a neuron (its action potentials) are shown plotted at the place where the animal was when the cell fired. This place cell has a "place field" in the North-East corner of the apparatus. (http://www.ucl.ac.uk/jefferylab/research)
The positioning and spatial navigation system
Electrophysiological experiments on rats have shown that there are neurones, 'place' cells, that fire when the animal was in one place in a room, with a different set of cells active when the rat was in a different area. These ‘place cells’ form a map of the room within the brain.
Other neurones recognise the precise position of the animal in its environment, while others allow for pathfinding, and the recognition of obstacles that might interfere with a desired trajectory. The neurones make it possible for the brain to determine position and spatial navigation.
There is extensive experimental data demonstrating the existence of 'boundary vector' cells that monitor the distance to obstacles and respond at a specific distance from barriers in the environment.
Boundary vector neurones, sometimes called 'border neurones' have been found in the subiculum and the medial entorhinal cortex.
The positioning system of the entorhinal cortex provides an understanding of how ensembles of specialised cells work together to execute higher cognitive functions, such as thinking, planning and memory.