Local field potentials

A local field potential (LFP) is an electrophysiological signal generated by the summed electric current flowing from multiple nearby neurons within a small volume of nervous tissue. Voltage is produced across the local extracellular space by action potentials and graded potentials in neurons in the area, and varies as a result of synaptic activity. "Potential" refers to electrical potential, or voltage, and particularly to voltage recorded with a microelectrode embedded within neuronal tissue, typically in the brain of an anesthetized animal or within a thin slice of brain tissue maintained in vitro.

During local field potential recordings, a signal is recorded using an extracellular microelectrode, placed sufficiently far from individual local neurons to prevent any particular cell from dominating the electrophysiological signal. This signal is then low-pass filtered, cut off at ~300 Hz, to obtain the local field potential (LFP) that can be recorded electronically or displayed on an oscilloscope for analysis. The low impedance and positioning of the electrode allows the activity of a large number of neurons to contribute to the signal. The unfiltered signal reflects the sum of action potentials from cells within approximately 50-350 μm from the tip of the electrode and slower ionic events from within 0.5–3 mm from the tip of the electrode. The low-pass filter removes the spike component of the signal and passes the lower frequency signal, the LFP.

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