For at least ten years, scientists have been trying to improve the condition of patients suffering from Alzheimer's or Parkinson's disease using a helmet emitting infrared towards the cranial box. In general, scientists use LEDs to be able to determine if the enhancement is related to a particular wavelength.
LEDs emit monochromatic and coherent light over a short distance, unlike lasers which can emit coherent light over a long distance, or lamps whose light is not at all coherent.
This caused a DIY movement of patients to assemble their infrared helmets with lamps or LEDs. You can also find helmets of this type on Aliexpress.
Do you have any recommendations, apart from SymByx's helmet (of which I am already aware)?