system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do we often get really weird, vivid dreams when we are sick? I've woken up from sleep while sick and had difficulty separating reality from what I just dreamed.
gpt
When you're sick, your body raises it's temperature because that can help fight off the infection. But, your brain is temperature sensitive. If it gets too hot, this can cause neurons to fire uncontrollably, basically creating seizures. This can lead to very vivd images and dreams forming in the brain because more of the brain "supports" what you think you saw.  A normal dream is quickly forgotten because you subconsciously realize that you lacked a lot context and sensory input to back up what you experienced.

This also applies to people with neurological disorders like MS.  They have to be careful when working out because if they get too hot, it can make their symptoms worse.