The human brain is considered the most complicated object in the universe, with its 100 billion neurons and more (possible) connections than the number of elementary particles in the known universe. It should surprise nobody, then, that the process by which this organ of seemingly infinite complexity refreshes itself, reboots as it were, is also very well studied. I allude, of course, to sleep.
I will not say anything about sleep itself here; one because I don’t know nearly enough to even start, and two, because I want the liberty, today, of not having to get everything factually right. So take this as a disclaimer that the following is just something interesting that I’ve observed with myself that I think you can repeat, but that I make no other claims.
That the brain is never fully ‘off’, that it never fully shuts down, is well-known. The brain is responsive to external stimuli even during sleep. This is how, for example, an alarm clock can awaken you. This is also how you can get ‘used to’ an alarm clock – if you don’t ‘want’ to get up someday, your brain is capable of ignoring the wails of the alarm clock. (Incidentally, I think this usually happens using some sort of confabulation. Go look up ‘confabulation‘ in the context of neuroscience!)
The following is an experiment that you can try on yourself when you feel like it. You will need to have a regular sleep cycle for this to work, though. I apologise if that rules out pretty much anybody who reads this blog! Anyway, if you have a regular sleep cycle, and sleep in a room which has some sort of window by which sunlight can get in, at dawn, this should work for you. This is a nice way of seeing how the brain responds to external stimuli even when one might think it has shut itself down.
A laptop is a good way of doing this, but I would wager that any light source whose intensity you can vary should work. Put your laptop facing you, preferably from the direction of the window in your room (you’ll see why shortly). You’ll have to arrange to have the display on throughout the night. You’ll have to also turn the brightness of the laptop display down as far as you can. If you do all this, you will see that you will consistently get up an hour or two earlier than you usually do (this is where the necessity that you have a regular sleep cycle comes in).
Do you see why?
Here’s the explanation I’ve cobbled up: at some point in the early morning, the ambient lighting in your room goes up beyond that you are used to getting up to. However, this happens earlier than usual because there’s already the light from the laptop. I usually get up at 7 am. If I keep my laptop on throughout the night at the lowest brightness setting, I can consistently get up at about 4:15.
Try it yourself and see if it works for you!