Each time you practice yoga nidra meditation, you’re stilling the waves of the mind through conscious entry into the sleep state. How?
You start with sensing the body and breathing in specific ways in order to trigger the relaxation response. The relaxation response balances the sympathetic and parasympathetic nervous systems, and balances the left and right brain. In the process, your brain shifts from beta, an awakened state with lots of brain activity, to alpha, a more relaxed state. In alpha, the mood-regulating hormone serotonin gets released, and this calms you down. People who spend little time in an alpha brain-wave state have more anxiety than those who spend more time in alpha. Think of a car: if you want to stop and turn off the engine, you first need to downshift. Shifting your brain into an alpha state starts its process of “powering down,” or coming into a rest state with slower, restorative brain-wave activity.