Exciting sodium ions in the brain with photons from electromagnetic radiation to produce a visible yellow glow, similar to that from a sodium-vapor lamp, is theoretically possible. The key requirement is a sufficient concentration of sodium ions; if the concentration is too low, the excitation may occur, but the light will not be visible. The visibility of the glow also depends on the frequency of the radiation used. For example, a yellow flame from sodium in a lab setting is achieved by providing the right amount of heat, which excites the electrons adequately to emit photons in the visible spectrum. Insufficient or excessive heat can prevent the necessary excitation for visible light emission.
