LORETA EEG phase reset of the default mode network

Area of Science:

• Neuroscience
• Computational Neuroscience
• Brain Imaging

Background:

• The default mode network (DMN) is crucial for internally directed thought.
• Understanding temporal dynamics within the DMN is key to deciphering brain function.
• Phase reset dynamics in neural networks are not fully understood.

Purpose of the Study:

• To investigate phase reset patterns of 3D current sources within human DMN Brodmann areas.
• To utilize Low Resolution Electromagnetic Tomography (LORETA) with electroencephalogram (EEG) data.
• To analyze phase dynamics in specific DMN regions.

Main Methods:

• Recorded EEG from 70 healthy adolescents (13-20 years) across 19 scalp locations.
• Computed time-resolved LORETA current sources for 14 DMN Brodmann areas in the delta band.
• Applied Hilbert transform to calculate instantaneous phase differences and derived phase shift/lock durations.

Main Results:

• Identified three discrete modes for phase shift durations: ~25 ms, ~50 ms, and ~65 ms.
• Observed primary phase lock durations between 300-350 ms and 350-450 ms.
• Found inverse relationship between phase shift/lock durations and exponential change with distance between Brodmann areas.

Conclusions:

• Results are explained by neural packing density of network hubs and distance-dependent connection decrease.
• Findings support a discrete temporal model of brain function.
• DMN hubs may act as shutters, opening/closing to create temporarily phase-locked neuronal clusters.