Local Field Potential (LFP)
Slow electrical signals reflecting population activity in nearby tissue.
Local field potential (LFP) is the low-frequency component of extracellular electrical recordings, typically below 300 Hz. LFPs reflect the summed synaptic activity, dendritic currents, and voltage-gated ion channels of many neurons near the recording site.
Why it matters: LFPs provide information about population dynamics, network oscillations (theta, gamma, etc.), and brain states that individual spikes cannot reveal. They're essential for understanding coordinated neural activity and brain-behavior relationships.
Signal characteristics:
- Frequency range: 1-300 Hz (some include up to 500 Hz)
- Amplitude: 10-1000 µV (larger than spikes)
- Spatial extent: Reflects activity within ~250 µm radius
- Source: Primarily dendritic and synaptic currents
Recording considerations: LFPs benefit from larger recording sites (lower impedance reduces thermal noise). Many researchers split signals into spike band (>300 Hz) and LFP band (<300 Hz) using analog or digital filtering.
Applications: Network oscillations, sleep states, attention modulation, seizure activity, brain-machine interfaces, anesthesia depth monitoring.