Spontaneous cortical DC-potential shifts: modulation stereotypy; relationships to higher EEG-frequencies

Area of Science:

• Neuroscience
• Electrophysiology
• Brain Activity Analysis

Background:

• Scalp-recorded spontaneous cerebral DC-potential shifts are poorly understood.
• Their relationship with higher brain frequencies (theta, alpha) and inter-hemispheric synchrony requires further investigation.

Purpose of the Study:

• To describe spontaneous cerebral DC-potential shifts.
• To analyze their relationship with higher frequencies (4-13 Hz) and pairwise synchrony across the median sagittal line (Fz, Cz, Pz).
• To compare DC-activity synchrony with higher frequency synchrony under relaxation and mental load conditions.

Main Methods:

• Analysis of spontaneous DC-potential shifts, independent of other variables.
• Pairwise analysis across Fz, Cz, Pz, considering frequency and condition (relaxation, mental load).
• Cross-correlation analysis between DC-potentials and theta, alpha 1, alpha 2 frequencies; dyad and triad context entropy for DC-shifts.

Main Results:

• Spontaneous DC-shifts were found to be unpredictable and random, particularly frontal shifts.
• Cross-correlation revealed high independence between DC-potentials and higher frequencies (average 9% common variance).
• DC-activity demonstrated higher synchrony than theta, alpha 1, alpha 2 frequencies, with overall high synchrony along the median sagittal line (75% average correlation > 0.60).

Conclusions:

• Cerebral DC-potential shifts are largely random and independent of higher brain frequencies.
• Despite independence, DC-activity exhibits greater synchrony than theta and alpha frequencies.
• High overall synchrony exists along the median sagittal line for both DC and higher frequencies.