Geometry of Navigation in Space: Neural Maps

 A cognitive map guides spatial navigation in mammals. Pyramidal neurons in the hippocampus become active only in a particular region of the environment. These regions are called ‘place fields’, and these neurons are called place cells. Many brain regions are involved in the cognitive mapping of the environment. Grid cells in the medial entorhinal cortex organize themselves on a regular grid of triangles covering the entire surface of the environment. The firing pattern of grid cells represents the distance between spatial locations. These distances provide spatial metrics for the cognitive map. Other neurons that participate in spatial navigation are head direction cells, border cells, speed cells, goal cells, reward cells, etc.

Hippocampus-entorhinal circuit provides a ‘coordinate system’ for on-line measurement of distance and direction of landmarks defining a path leading to a goal. Navigation of an animal toward a goal depends on synaptic plasticity. Functional synapses are chosen from a set of anatomical synapses based on the interaction of Hebbian learning rules, sensory feedback, attractor dynamics, and neuromodulation. Artificial neural networks, which emulate biological neural networks, can be derived from complete connectomes of an organism. Design and control principles underlying intelligent autonomous control systems can be understood based on an analysis of these ANNs.