system
Given the following post, respond as if you're commenting on Reddit:
human
How do we distinguish between sounds in our head and sounds in the real world?

Example: Say you thought of a song, Psycho Killer for example, and you think about that song in your head. You can sort of hear the song in your head. How do we tell the difference between these sounds and sounds we hear in the real world?
gpt
There are a large chain of neurons from the ear to the auditory cortex. Cochlear nucleus- olivary complex- inferior colliculus- medial geniculate body of the thalamus- auditory cortex. While these are a two way street in some regard, thinking of songs in your head would have less activation in the first three nuclei than actually hearing sounds do. These brainstem neurons are also what's responsible for the startle reflex, which bypasses the rest of the pathway and gets us moving in less than 50ms as opposed to the ~200 that the normal pathway takes. Therefore they have a direct signal to some part of the brain that basically says "sound coming through ear". Source M.S. Neuroscience. If you want actual sources try principals of neuroscience by Eric kandel. It's like three dictionarys strapped together though.