Influence of spiking activity on cortical local field potentials

Area of Science:

• Neuroscience
• Electrophysiology
• Computational Neuroscience

Background:

• Local field potentials (LFPs) are widely used to study neural activity, reflecting synaptic inputs and neuronal spiking.
• A common practice is to filter LFPs above 300 Hz to remove spiking activity, assuming this adequately isolates synaptic processes.
• However, the extent of spike contamination in LFPs and its impact on data interpretation remain significant concerns.

Purpose of the Study:

• To investigate the extent to which neural spikes contaminate intra-cortical local field potentials (LFPs).
• To identify factors influencing spike contamination in LFPs.
• To develop and present a method for assessing and visualizing spike contamination in LFP data.

Main Methods:

• Analysis of intra-cortical spikes recorded from the motor cortex of awake monkeys.
• Investigation of factors such as spike amplitude, duration, firing rate, and noise statistics.
• Development of a novel method to detect and visualize spike contamination in LFP signals.

Main Results:

• Spike contamination of LFPs is demonstrated to be significant, extending to frequencies as low as approximately 10 Hz.
• Contamination is theoretically possible but unlikely for LFP activity below 10 Hz (e.g., movement-related potentials).
• LFP frequencies up to the high-gamma band can remain unaffected by spike contamination.

Conclusions:

• Standard high-frequency filtering of LFPs is insufficient to eliminate spike contamination.
• Spike-LFP crosstalk can lead to erroneous conclusions in neurophysiological studies.
• Individual assessment of spike contamination using the proposed method is essential for validating LFP analysis and ensuring reliable interpretations of neural activity.