The majority of autistic people experience atypical sensory processing to some degree. This doesn’t necessarily mean that we are always sensitive to certain sensations or input. Atypical sensory processing simply means that sensory input can be experienced as either a hyper or hypo reaction.
Something that seems to play a critical role in how we perceive sensory stimuli is the concept of sensory gating. Sensory gating, also known simply as gating, is essentially a way for our brains to weed out unnecessary stimuli coming our direction, so it can help us focus on the “important” things.
It basically prevents our brains from becoming overloaded. It’s like a series of floodgates of sorts, that can be controlled, opened and closed, like a dam. All at once, a few of these “dams”, or gates are opened to allow what our brain deems important or relevant sensory information to pass through, while other gates remain closed to ensure that information which is seemingly unimportant gets filtered out. Our brains constantly do this adjusting all on their own, like magic. They consistently make adjustments to ensure what’s supposed to get through does, and what’s not doesn’t.
The majority of peoples’ brains would interpret extraneous stimuli (such as dogs barking, air blowing from a vent, rain hitting the window, hair brushing against the back of the neck, etc.) as being unimportant and would automatically close their sensory gates, making sure that the sensory input wouldn’t prove to be a distraction and a neurotypical person would actually probably need to try to make note of those sensations, as if they were engaging in a sort of meditation or something, in order to actually be able to recognize them.
For those of us who are autistic however, we often experience each of these things all. at. once. I’m not having to stop and think, “what do I hear, feel, smell, see, etc.”? It’s just all there and it doesn’t stop for us to finish the “important” things.
The ways in which sensory information is processed by our brains is not well understood. Often for the autistic brain, once sensory information passes through the gate, it goes through further filtering so it can travel to the necessary parts of our brains. For instance, it may travel to our limbic system which is responsible for our emotions (pleasure, fear, anger, etc.) and drives (hunger, sex, etc.). As this input is filtered, the various parts of our brain are able to communicate with one another.
The autistic brain still engages in this filtration process, but it goes about it a bit differently. Rather than the sensory information that passes through the gate being solely relevant, it’s a mixture of relevant and irrelevant. Since EVERYTHING gets processed in this way and much of what’s processed isn’t ordered in terms of relevance, our incoming sensory experiences can turn out to be a bit uneven.
All of the other little things going on around us can seem to us to be at the same volume or level of intensity as someone speaking right in front of us. All of these inputs being simultaneously processed by the brain can very easily result in sensory overload.