Relationships between spike-free local field potentials and spike timing in human temporal cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Electrophysiology

Background:

• Intracortical recordings capture fast action potentials (APs) and slower local field potentials (LFPs).
• LFPs are thought to reflect synaptic activity, but their precise relationship with AP occurrence, especially concerning LFP frequency components, remains unclear.
• AP waveforms can contaminate LFP signals, complicating analysis.

Purpose of the Study:

• To investigate the relationship between specific LFP signal components and the timing of individual APs.
• To determine which LFP features causally relate to synaptic potentials and AP occurrence.
• To model the prediction of AP timing from LFPs, considering the impact of AP contributions.

Main Methods:

• Quantitative, nonlinear, causal dynamic models were developed to predict AP timing from LFPs in human temporal cortex recordings.
• Models were evaluated both with and without the removal of AP contributions from the LFP signal.
• Analysis focused on millisecond-resolution data to discern fine-grained temporal relationships.

Main Results:

• Significant numbers of single AP timings were predictable from spike-free LFPs across various frequencies.
• Model performance was better when AP contributions were not removed from LFPs.
• Two distinct groups of cells emerged: one associated with low LFP frequencies and phase locking, the other with high LFP frequencies and power.
• Spike timing prediction differed between groups, relying on preceding LFP sign/level or LFP power, respectively.

Conclusions:

• Specific LFP components, even after spike removal, contain predictive information about neuronal firing timing.
• The relationship between LFPs and APs is complex and can be categorized into distinct neuronal response patterns.
• Dynamic modeling of LFPs offers insights into synaptic mechanisms underlying action potential generation.