Ephaptic Coupling of Cortical Neurons: Possible Contribution of Astroglial Magnetic Fields?

The close anatomical and functional relationship between neuronal circuits and the astroglial network in the neocortex has been demonstrated at several organization levels supporting the idea that neuron-astroglial crosstalk can play a key role in information processing. In addition to chemical and electrical neurotransmission, other non-synaptic mechanisms called ephaptic interactions seem to be important to understand neuronal coupling and cognitive functions. Recent interest in this issue comes from the fact that extra-cranial electric and magnetic field stimulations have shown therapeutic actions in the clinical practice. The present paper reviews the current knowledge regarding the ephaptic effects in mammalian neocortex and proposes that astroglial bio-magnetic fields associated with Ca2+ transients could be implicated in the ephaptic coupling of neurons by a direct magnetic modulation of the intercellular local field potentials.