Found an interesting snippet whilst looking at binaural beats
Resetting Your Brains Sodium/Potassium Ratio In Theta
Your brain cells reset their sodium & potassium ratios when the brain is in
Theta state. The sodium & potassium levels are involved in osmosis which
is the chemical process that transports chemicals into and out of your brain
cells. After an extended period in the Beta state the ratio between
potassium and sodium is out of balance. This the main cause of what is
known as "mental fatigue". A brief period in Theta (about 5 - 15min) can
restore the ratio to normal resulting in mental refreshment.
Does anyone know more about this ? and is it what I understand as the
ultradian cycle ? ( I have 0 knowledge of biology/chemistry,etc )
Thanks