through Hebbian learning. But grid cells may perform a more supporting role in the formation of place fields, such as path integration input. Another non-spatial explanation of hippocampal function suggests that the hippocampus performs clustering of inputs to produce representations of the current context – spatial or non-spatial. Properties Place fields Place cells fire in a specific region of an environment, known as a place field. Place fields are roughly analogous to the receptive fields of sensory neurons, in that the firing region corresponds to a region of sensory information in the environment. However, unlike receptive fields, place cells show no topography, meaning that two neighboring cells do not necessarily have neighboring place fields. Place cells fire spikes in bursts at a high frequency inside the place field, but outside of the place field they remain relatively inactive. Place fields are allocentric, meaning that they are defined with respect to the outside world rather than the body. By orienting based on the environment rather than the individual, place fields can work effectively as neural maps of the environment. A typical place cell will have only one or a few place fields in a small laboratory environment. However, in larger environments, place cells have been shown to contain multiple place fields which are usually irregular. Place cells may also show directionality, meaning they will only fire in a certain location when travelling in a particular direction. Remapping Remapping refers to the change in the place field characteristics that occurs when a subject experiences a new environment, or the same environment in a new context. This phenomenon was first reported in 1987, and is thought to play a role in the memory function of the hippocampus. There are broadly two types of remapping: global remapping and partial remapping. When global remapping occurs, most or all of the place cells remap, meaning they lose or gain a place field, or their place field changes its location. Partial remapping means that most place fields are unchanged and only a small portion of the place cells remap. Some of the changes to the environment that have been shown to induce remapping include changing the shape or size of the environment, the color of the walls, the smell in the environment, or the relevance of a location to the task at hand. Phase precession The firing of place cells is timed in relation to local theta