Dr. Ray Peat said:"Nerves are always regenerating, and thyroid, pregnenolone, and progesterone are needed for good development and repair. One kind of exercise that's helpful is to watch a bead on a thread, as you move it from close to your nose to a yard or more away (a yardstick can be used similarly). Visualization exercises with your eyes closed, for example for a few minutes after you wake up in the morning. Watch any visual events that you happen to notice; noticing them will cause them to change. At certain levels of relaxation and arousal, your visual system will show you some of the operating principles, scanning motions, for example. Coffee, thyroid, and progesterone affect the things you will notice with your eyes closed. At different times you will see things that seem to be on a flat screen, other times you will notice depth. One type of visual event you will notice is fine-grained, and is the activity of the retinal nerves; the more spatial things involve the optic nerve and visual cortex. Just attending to the spontaneous events affects the nerves' functions and development."