I believe this is not quite right. I think it's due to the blood brain barrier. Brain tissue has only limited capability for anaerobic respiration compared to

I believe this is not quite right. I think it's due to the blood brain barrier. Brain tissue has only limited capability for anaerobic respiration compared to the rest of the body, can't metabolise fats for energy, and has no ability to store glycogen (which happens in muscle tissue and the liver), so any glucose has to get sent up there by other systems.