This can be accomplished using the tetrode, typically made by winding together four ultrathin wires. Having multiple adjacent recording sites permits the triangulation and isolation of a large number of single units in freely-moving animals.  By using this technique to record from neuronal ensembles in the medial temporal lobe memory structures of young and aged animals, researchers at NCAM hope to uncover novel mechanisms for age-related changes in cognition.

Fig. 1, right: A hippocampal place cell isolated by tetrode recording. Upper panel shows the path taken by an animal foraging for food in an open field (gray) and the locations in which a recorded neuron fired (red). Lower panel shows the corresponding color-coded rate map for this cell.