What’s happening when you think there’s a bug crawling on your leg, but nothing’s there?
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Your brain has the ability to filter what it thinks is not important sensation, called sensory gating — like how you don’t feel facial hair after a few weeks of having it, or not feeling your shoes constantly, etc. There are various optical illusions related to this function.
There probably isn’t anyone that fully understands what criteria is required before the brain passes data to the sentient thought portions, but it’s definitely affected by mood — like when people watch a movie with bugs in it and are creeped out and swear they feel them.
Chances are, some sensation your body would typically ignore failed the vibe check.
IE., sometimes it’s leg hair.
Your nerves often send random false signals but the brain decides to ignore some of them when they’re not important.
however, some signals that are more important than others are not ignored.
feeling a bug crawling on your leg is not something to be ignored even if it’s a false sensation, because bugs can be poisonous or carry disease, so the brain would rather be safe than sorry.
another example is the false sensation of something vibrating on your skin: historically the brain would ignore such feelings when there was no reason for them to exist. However, since the invention of the mobile phone, vibrations on your legs are now an important signal because a vibration in your pocket means you’re receiving a call.
so nowadays the brain no longer ignores such sensations which leads to phantom vibrations in your legs, particularly on the side of the body where you normally keep you phone.
https://www.webmd.com/a-to-z-guides/news/20160111/phones-phantom-vibration
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Parasthesia(s). Can be triggered by changes in the nervous system or circulation. Neurotransmitters can innervate nerves, anxiety can release hormones that trigger certain nerves.
Anxiety of a bug landing on you inducing phantom bug tickles? Possible. Someone else said wind. If you had a bug land on you, you anticipate more – this anticipatory excitement (anxiety) makes you more “nervous” which essentially means nerve sensitivity is increased.
But yeah, can be many things tripping a nerve impulse.
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Your brain is basically a machine that compares two models of external reality- the model created by your senses, and a predictive model that guesses what the sensory model is going to look like. If that sounds weird it’s because it is.
When you feel a phantom bug on your leg, its because your sensory model showed some movement on your leg- wind brushing your hair or something- and the predictive model thought that seemed like the sort of data that would show up when a bug starts to walk on you, so it predicts that the sensory data will continue along those lines. So the predictive model adds a “bug walking on your leg” sensation, and you literally experience that sensation for a brief moment before the sense data shows that there isn’t actually a bug.
I see people in the comments talking about how autism can cause a really irritating form of this phenomenon where the bug crawling sensations keep coming back over and over again- there are some interesting hypotheses about autism and how it may in part be a pathology of the sensory/predictive models where the balance is thrown off in favor of the sensory model and the predictive model can’t smooth over irrelevant stuff or stuff that doesn’t make sense. Hence autistic people continually feeling the lining or tags on socks and clothes- the predictive model is being constantly outweighed by the sensory model and it can’t, as it does in neurotypical people, whiteout the irritating sense data from the tag.
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really tiny, TINY bugs that move your tiny body hairs (you can’t see them, so small!)
ok no not really but enjoy your skin crawl
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