Sparse asynchronous cortical generators can produce measurable scalp EEG signals

Area of Science:

• Neuroscience
• Computational Neuroscience
• Biophysics

Background:

• Scalp electroencephalography (EEG) is widely used to study brain activity.
• The relationship between underlying cortical activation and observable scalp EEG signals is complex.
• Current interpretations often assume synchronous cortical activity for EEG generation.

Purpose of the Study:

• To determine the necessity of synchronous, smooth cortical activation for generating scalp EEG.
• To compare different models of cortical activation and their impact on scalp EEG.
• To investigate the influence of spatial and temporal activation patterns on EEG signals.

Main Methods:

• Extensive computational simulations of cortical activation models.
• Modeling spatial activation as smooth patches or random small generators (0.1-3cm²).
• Modeling temporal activation with equal or random phase across generators.

Main Results:

• Smooth and random spatial activation profiles yield similar scalp electric potential distributions.
• Random phase oscillatory activity from multiple generators results in scalp activity attenuated only 2-4 times compared to equal phase.
• Sparse, asynchronous cortical generators can produce measurable scalp EEG.

Conclusions:

• Scalp EEG signals can be generated by sparse and asynchronous cortical activity.
• The assumption of smooth, synchronous cortical activation may be an oversimplification.
• This finding offers a potential explanation for paradoxical observations of disorganized intracranial activity and scalp EEG.