If I understood that correctly (not entirely sure I did), this is indeed part - minus the (emotional) breakdown - of my autism and I dare say a common part of ASDs in general (as well as other disorders).
My brain gets overloaded from too many stimuli and sensory processing - due to my abnormal openness to stimuli - is slowed down to active concious (and often slow) figuring out of sounds, visual, tactile stimuli, so on.
For others, emotions or even physical exhaustion more commonly lead to the same issue of being overloaded by "too much going on" to cope with anymore after a certain point.
My (otherwise quite good) cognitive abilities are almost always affected to some degree by because I'm getting overloaded all the time, pretty much everywhere. My ability to talk is often temporarily affected. Moving can be too, too many stimuli interfere with walking/standing, so on.
Others seem to experience negatives effects (from being a little slow in a busy, hectic environment to a complete temporary loss) to calculate, read, think coherently, figure out a difficult (theoretical) problem, understanding other people, so on.
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Autism + ADHD
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The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it. Terry Pratchett