Phase-amplitude coupling between low-frequency scalp EEG and high-frequency intracranial EEG during working memory...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Cognitive Science

Background:

• Simultaneous scalp electroencephalography (EEG) and intracranial electroencephalography (iEEG) are crucial for understanding brain function.
• The relationship between prominent iEEG high-gamma band features and scalp EEG remains largely uninvestigated.

Purpose of the Study:

• To investigate phase-amplitude coupling (PAC) between low-frequency scalp EEG and high-gamma iEEG.
• To determine if high-frequency iEEG activity can be reflected by non-invasive scalp EEG.

Main Methods:

• Analysis of simultaneous iEEG and scalp EEG data from nine epilepsy patients during a verbal working memory task.
• Exploration of PAC values between scalp EEG channels and iEEG channels.
• Comparison of PAC values across different task periods (encoding, maintenance, retrieval) and memory loads.

Main Results:

• High-gamma amplitude in the entorhinal cortex, hippocampus, and amygdala correlated with delta or theta phase at scalp locations (Cz, Pz).
• Maximum PAC occurred between 3.16-3.84 Hz (phase) and 50-85 Hz (amplitude).
• PAC values were significantly higher during retrieval than encoding or maintenance and were influenced by memory load.

Conclusions:

• This is the first human study demonstrating PAC between iEEG high-gamma amplitude and scalp EEG low-frequency phase.
• Findings enhance understanding of multiscale neural interactions in working memory.
• Provides a non-invasive method to estimate intracranial high-frequency features.