" The healing effect of light at low power and energy density can be used as a treatment or alternative supportive method in various diseases. The photobiostimulation effect created on neural cells is also a very promising approach in the treatment of important neurodegenerative diseases such as Alzheimer’s disease. In this study, the response of PC12 cells to photobiomodulation was investigated as a result of the low level laser therapy with 655 nm diode laser after triple treatment. The red light at an energy density of 1, 3 and 5 J/cm2 was applied to PC12 cells three times with 24h intervals. The differentiation capacity of the cells and the elongation rates of neurites were assessed. The neurite lengths were calculated by analyzing the microscopic images of the cells. Neurite-forming capacity and differentiation rate of PC12 cells was at the maximum level after the application with 1 J/cm2 energy, nearly 2 times of the control group. 5 J/cm2 of energy density strongly inhibited the cell proliferation and the elongation of the neurites. The cell viability percentages of the cells showed that 5 J/cm2 energy density inhibited cell viability with a rate of nearly 30%."
One of the surprising outcomes is that the most prominent desired effect is reached not at the maximum energy density exposure but at the lowest. This is not the only case, we can see it in other light exposure experiments and also in other kind of exposures like those to extremely low frequency electromagnetic fields  or, for example, to static magnetic fields  where it is clear that biological systems decide, based on the intensity of the field, that the sensend field is an information field if it's in the range of the geomagnetic field, but decides that is noise if the intensity is outside the natural range, and try to ignore it, at least volitionally.
 Prihandono, T., Ridlo, Z. R., & Kristinawati, A. (2018, November). Effective dose analysis of extremely low frequency (ELF) magnetic field exposure to growth of S. termophilus, L. lactis, L. acidophilus bacteria. In Materials Science and Engineering Conference Series (Vol. 432, No. 1, p. 012010).
 Yan, J. L., Zhou, J., Ma, H. P., Ma, X. N., Gao, Y. H., Shi, W. G., ... & Chen, K. M. (2015). Pulsed electromagnetic fields promote osteoblast mineralization and maturation needing the existence of primary cilia. Molecular and cellular endocrinology, 404, 132-140.
 Vale, J.O. and Acosta‐Avalos, D. (2020), Magnetosensitivity in the Stingless Bee Tetragonisca angustula: Magnetic Inclination Can Alter the Choice of the Flying Departure Angle From the Nest. Bioelectromagnetics. https://doi.org/10.1002/bem.22312
Last modified on 20-Dec-20