Millisecond Coupling of Local Field Potentials to Synaptic Currents in the Awake Visual Cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Electrophysiology

Background:

• The cortical local field potential (LFP) is widely used to measure population neural activity.
• The precise relationship between LFP and synaptic activity in individual neurons remains unclear, particularly during naturalistic behaviors.
• Previous studies were often limited by anesthesia, which can obscure neural dynamics.

Purpose of the Study:

• To investigate the relationship between cortical LFP and intracellular neuronal activity.
• To differentiate the roles of excitation and inhibition in this relationship across anesthesia and wakefulness.
• To develop a method for analyzing LFP-neuronal coupling.

Main Methods:

• Patch-clamp recordings of intracellular activity in the visual cortex of anesthetized and awake mice.
• Simultaneous recording of the cortical local field potential (LFP).
• Application of a novel analytical method to quantify LFP-neuronal coupling.

Main Results:

• LFP predicted neuronal membrane potential with accuracy comparable to synaptic currents.
• During anesthesia, LFP better predicted excitatory synaptic currents than inhibitory ones.
• During wakefulness, LFP equally predicted both excitatory and inhibitory currents, with visual stimulation enhancing inhibition prediction.

Conclusions:

• Synaptic currents play a critical role in the relationship between cortical LFP and intracellular neuronal activity.
• The balance of excitation and inhibition influencing LFP differs between anesthesia and wakefulness.
• Inhibition significantly contributes to LFP dynamics during wakefulness, especially under sensory stimulation.