Coupled neuro-fluid dynamics in human bioelectromagnetism

Electroencephalography (EEG) and magnetoencephalography (MEG) are often considered direct, non-invasive measures of neural activity. However, recent research suggests that surrounding tissue and cerebrospinal fluid (CSF) play a more significant role than previously thought. Conductive-fluid phantom experiments, combined with structural MRI and live EEG/MEG recordings, have shown that mechanically driven conductive fluid can create structured, oscillatory electromagnetic signals similar to those seen in the brain, even without neural tissue present.

The study also found that differences in CSF volume among individuals can greatly influence M/EEG signal amplitude, indicating that the electromagnetic and mechanical processes in the brain are deeply interconnected. At the scales accessible to both invasive and non-invasive electrophysiological techniques, these two aspects of brain function appear to form a coupled system, making it difficult to separate the contributions of neural currents and fluid motion.