Place cell

[1] Place cells work with other types of neurons in the hippocampus and surrounding regions to perform this kind of spatial processing.

And they seem to perform consolidation by exhibiting replay – the reactivation of the place cells involved in a certain experience at a much faster timescale.

To test this hypothesis, they developed chronic electrode implants, with which they could record the activity of individual cells extracellularly in the hippocampus.

They noted that some of the cells showed activity when a rat was "situated in a particular part of the testing platform facing in a particular direction".

[10] There has been much debate as to whether hippocampal place cells function depends on landmarks in the environment, on environmental boundaries, or on an interaction between the two.

[16] Recent findings, such as a study showing that place cells respond to non-spatial dimensions, such as sound frequency, disagree with the cognitive map theory.

[15] But grid cells may perform a more supporting role in the formation of place fields, such as path integration input.

[32] The firing of place cells is timed in relation to local theta waves, a process termed phase precession.

[33] It is thought that this phenomenon increases the accuracy of the place coding, and aids in plasticity, which is required for learning.

For example, the receptive fields become skewed when rats travel a linear track in a single direction.

[38] Place cells were initially believed to fire in direct relation to simple sensory inputs, but studies have suggested that this may not be the case.

[15] This suggests that place cells respond to complex stimuli rather than simple individual sensory cues.

Metric and contextual inputs are processed together in the entorhinal cortex before reaching the hippocampal place cells.

A change in color of a specific object or the walls of the environment can affect whether or not a place cell fires in a particular field.

[41][42][43] Olfaction may compensate for a loss of visual information,[41][43] or even be responsible for the formation of stable place fields in the same way visuospatial cues are.

Mice use their self-motion information to determine how far and in which direction they have travelled, a process called path integration.

[49] By establishing spatial context, place cells play a role in completing memory patterns.

[50][51] Pattern completion is the ability to recall an entire memory from a partial or degraded sensory cue.

[51] Place cells are able to maintain a stable firing field even after significant signals are removed from a location, suggesting that they can recall a pattern based on only part of the original input.

[15] Furthermore, the pattern completion exhibited by place cells is symmetric, because an entire memory can be retrieved from any part of it.

[15] Pattern separation begins in the dentate gyrus, a section of the hippocampus involved in memory formation and retrieval.

[52] Granule cells in the dentate gyrus process sensory information using competitive learning, and relay a preliminary representation to form place fields.

[52] Place fields are extremely specific, as they are capable of remapping and adjusting firing rates in response to subtle sensory signal changes.

This reactivation has a much faster time scale than the actual experience, and it occurs mostly in the same order in which it was originally experienced, or, more rarely, in reverse.

[53] However, when replay is disturbed, it does not necessarily affect place coding, which means it is not essentially for consolidation in all circumstances.

[60] Rats became especially popular after the development of multiarray electrodes, which allows for the simultaneous recording of a large number of cells.

[66][67] Place cells were reported in Egyptian fruit bats for the first time in 2007 by Nachum Ulanovsky and his lab.

[79] Place cells have been shown to degenerate in Alzheimer's mouse models, which causes such problems with spatial memory in these mice.

However, this observed place field expansion and plasticity is decreased in aged rat subjects, possibly reducing their capacity for spatial learning and memory.

The application of memantine leads to in increase in place field plasticity in aged rat subjects.