COMPLEX-VALUED PHASE SYNCHRONY REVEALS DIRECTIONAL COUPLING IN FMRI AND TRACKS MEDICATION EFFECTS

Area of Science:

• Neuroscience
• Complex Systems Analysis
• Signal Processing

Background:

• Understanding complex systems requires quantifying directional coupling, not just strength.
• Existing phase synchronization methods often lose directional information by reducing phase to scalar values.
• Accurate phase estimation is crucial for analyzing dynamic interactions in systems like the brain.

Purpose of the Study:

• To introduce a novel framework, complex-valued phase synchrony (CVPS), for estimating directional coupling.
• To preserve both cosine and sine components of phase for a more complete representation of timing.
• To evaluate CVPS's ability to capture pharmacological effects on neural timing.

Main Methods:

• Utilizing an adaptive Gabor wavelet for phase estimation within the CVPS framework.
• Comparing CVPS performance against Hilbert-based methods in simulations.
• Applying CVPS to analyze cortical neuro-hemodynamic interactions under pharmacological influence.

Main Results:

• CVPS accurately recovers true phase offsets and tracks non-stationary dynamics better than Hilbert methods.
• Simulations confirm the robustness and faithfulness of CVPS phase estimation.
• CVPS successfully captured pharmacological timing effects of antipsychotics on cortical interactions.

Conclusions:

• CVPS provides a robust and generalizable method for detecting directional coupling in complex systems.
• The framework accurately captures neuro-hemodynamic drivers and lead-lag flows in the brain.
• CVPS offers a valuable tool for studying timing in neuroscience and other complex systems.