Eli5: Why can’t we hear our environment while we are asleep?
In: Biology
Your brain is actually two layers.
The top layer – neocortex (new brain) – is mostly unique to mammals. This is what gives us emotions and forms family bonds and let’s us think.
The bottom layer is commonly called your “lizard brain”. It is pure instinct. No thought. But, that makes it much much faster to react.
All your senses filter through your lizard brain. This part runs a quick threat analysis and if it thinks there is a threat, will react accordingly. This is why you might be walking in the park and jump in fright only to realize it’s a stick not a snake. Your brain did a quick assessment and determined there was enough of a threat of a snake that you should jump back. If it waited for a full determination to make sure it really was a snake and it was actually dangerous it might take seconds which is far too slow.
Right, so on to sleep. All day you train your brain on what sounds in your house are dangerous and which are normal. Then when you sleep, your lizard brain is filtering through and only reacting to what is dangerous. This is also why a night in a new place isn’t as restful. Your brain is working extra hard on all the unfamiliar sounds.
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