Loss–amplification-radiation coupling model of the mid-infrared signal propagating in demyelinated axons

Many neurological disorders are associated with demyelination, leading to abnormalities in neural signal transmission. This study presents a loss-amplification-radiation coupling model for the transmission mechanisms of terahertz and infrared signals in demyelinated axons with disruption and rupture. Demyelinated axons are treated as dielectric antennas, and the radiation characteristics at different degrees of demyelination are investigated through simulations in the frequency range of 55-75 THz. The results indicate that radial demyelination tends to increase radiation more significantly than axial demyelination. The directivity and radiation efficiency reach 18.76 dBi and -1.17<i>d</i><i>B</i> for severe demyelination (<i>L</i>_d/<i>L</i>>0.5 and <i>t</i>_d/<i>t</i>>0.5), respectively. Ruptured myelin axons can maintain signal transmission within a certain distance of less than 15 µm in the simulation. These results are consistent with previous studies and may enhance the understanding of mid-infrared signal propagation mechanisms in nerves, as well as contribute to research on diseases associated with demyelination, such as multiple sclerosis and Alzheimer's disease.