Challenges in the quantification and interpretation of spike-LFP relationships

- Extracellular voltage represents the transmembrane activity of many neurons.
- Local field potential (LFP) can be used to capture intracellular rhythmic activity.
- Along with the rhythm, LFP also captures several other events related to a spike.
- Contribution of these events in the LFP and their removal techniques are discussed.

Brain signals often show fluctuations in particular frequency bands, which are highly conserved across species and are associated with specific behavioural states. Such rhythmic patterns can be captured in the local field potential (LFP), which is obtained by low-pass filtering the extracellular signal recorded from microelectrodes. However, LFP also captures other neural processes that are associated with spikes, such as synaptic events preceding a spike, low-frequency component of the action potential (“spike bleed-through”) and spike afterhyperpolarization, which pose difficulties in the estimation of the amplitude and phase of the rhythm with respect to spikes. Here we discuss these issues and different techniques that have been used to dissociate the rhythm from other neural events in the LFP.