For some time, I’ve been noticing a strange sensing phenomenom. Here’s how it typically goes:
I’m lying in bed, half-awake, listening to the radio. The air conditioning unit turns on and makes a pop! sound. At the same time as the pop!, I perceive a visual flash. Then I perceive the audial pop!.
More details:[ul]
[li] I’m always in relaxed state, either half-awake/half-asleep, or in meditative state.[/li][li] My eyes are always closed.[/li][li] The pop! has come from several sources: AC, refrigerators, car back-fires, slammed doors. Basically, any short, loud sound.[/li][li] The flash is always perceived (slightly) before the pop!.[/ul][/li]
So, does anyone else experience this sort of thing? Any theories to what’s going on? Do I need to see a neurologist?
I have two guesses to the cause:[ol]
[li] I have a couple crossed neural paths. So a strong audial signal crosstalks into my visual wiring.[/li] My eyes do an autonomous flinch when there’s a loud sound. The produces visual stimulation also.[/ol]
You may be experiencing what’s known as synaesthesia
Thanks, Mangetout, that was an excellent lead. My experience is not as intense as a true synaesthesian, but it’s the same basic phenomenom.
Yes! I get this, but usually only when there is a loud noise when I am in bed just before sleep - I get a white flash in my vision, which certanly wakes me up pretty quickly to see what made the noise- maybe its a self defence mechanism.
Your symptoms are fairly common, and are probably what are called “Sleep Starts,” due to a poorly defined hyperexcitablity of the central nervous system as you fall asleep. A frequent co-symtom is a lightening-like jolt that results in adduction spasm of the legs. If you have this, you are almost certainly experiencing a hypnogogic sleep starle response. This hyperexcitability is more common when you are exhausted and “stressed out.”
Synesthesia is a relatively rare phenomenon. It seems to be due to abnormal interconnections between normally separate sensory circuits—e.g. the person who “hears” or “tastes” colors, etc., etc.
Could it be more of a “Sleep Ends”? The symptons appear usually in the late afternoon/early evening after I’ve taken a 10-20 minute rest/nap/meditation. It’s in more of a becoming-more-active state, not a becoming-less-active one. I’ve never had any physical motion associated with it.
It’s good to hear about the variety of different sensations that people experience.
No, it’s not synaesthesia, nor sleep starts.
It’s just an autonomic reaction to being mildly startled, the same as the “fight or flight” reaction, just to a lesser degree. This is causing your irises to momentarily dilate and allow more light in. You perceive this as a “flash.”
So yes, in a way you could say you have your “neurons crossed.” But they’re supposed to be crossed that way.
As for the relative timing of your wisual and aural perceptions, I cannot guess - but a large portion of the brain is devoted to visual processing, more than for sound (and there’s a lot of that, too). Perhaps that has something to do with it.
When I read this phrase, I have an involuntary image of Walter Koenig. Does this mean that my neurons are crossed?
I’m wondering why bughunter ruled out sleep starts.
I like bughunter’s explanation the best so far. I can test the iris hypothesis by checking if there’s no longer a flash when I’m in a completely darkened room.
He probably ruled out sleep starts because of my previous comments. I think there’s some element of hyper-excitability, in that I only notice the effect when I’m in a relaxed state (so there’s a lack of other stimuli). But the the stress-out and physical-motion elements of the sleep start don’t really fit my case.
This sounds like a serious pathology. See a doctor at once. 
Exactly.
And also, sleep starts do not occur in response to external stimulus. I get them myself sometimes.
(I once sleep started so violently I kicked the wall next to my bed and broke my toe. I didn’t fall asleep anytime soon after that!)
Heh. I don’t know how I did that. The w is nowhere near the v – talk about crossed neurons! I need to have my motor cortex examined.