Pyramidal cells in the rodent hippocampus fire in a spatially localized manner. The Nobel prize was recently award to John O’Keefe for his discovery of such “place cells”. A typical place cell will fire action potentials at a rate varying from zero Hz when the animal is outside of its “place-field” to up to 40 Hz when the animals is at the most “preferred” location of that cell.
Despite this tremendous advance, much remains unknown about how place-cell activity allows the hippocampus to encode episodic memory, in which it plays a well-established role.
In our lab, we use the sequential firing of place cells, when a rat run across an environment, to create a mnemonic sequence template that gives the hippocampal neural correlate of the rodent’s experience. We observed forward and reverse replay of the experiential place-cell sequences during rest epochs, when the rat was no longer running.