Extracellular measurement capture lower spike amplitudes, often from several sources (depending on the size of the electrode and its proximity to each spiking source). Despite the degraded amplitude of these measurements, they have some advantages: 1) They are experimentally easier to obtain 2) Robust and last for a longer time. 3) Capturing the activity of several neurons can potentially emphasize the dominant effect over accidental phenomenon due to the inherent spatial averaging.