On an Analogy Between Ephaptic Coupling in Large Tracts and Cross-Modal Integration During Illusory Percept

In this paper, the authors report simulations analogous to cross-modal integration which can be modeled by thinking of large (in terms of numbers of axons) axon tracts with distinctly demarcated subsets of axons. In such a tract, when the demarcated regions are separately stimulated they fire in response to the stimulation. Due to extracellular current-based coupling, at a later time, unstimulated axons also begin to cross-talk. The simulation graphical result, though on a faster time scale, is analogous to the multi-channel MEG recordings of "AV-(A+V)" obtained by Shams et. al. When the coupling parameter is weakened, this cross-talk disappears. In Shams et. al., the appearance and disappearance of cross-talk are related to the perception of an illusory flash by the subject. Our extrapolated conclusion is that ephaptic coupling might be a part of the mechanism for cross-talk between brain regions mediating, say, audio and visual-processing. We also study noisy ephaptic coupling and additionally do a comparative study with the Kuramoto model, which yields insight into the exact and detailed mechanism of ephaptic synchronization.