How to keep our surroundings clean?

What is the scientific explanation behind somnambulism? How does the brain keep an accurate visual map of a person's surroundings?

• Sleep Walking is called somnambulism  Adding additional details to the question; As portrayed in most movies how is it that,the sleeper always precisely know the exact location of empty places in a house? How do they manage not to bump into obstructions?

• Answer:

  Sleep walking is not much different from regular walking: The person is walking with their eyes open, so the visual cortex is receiving the needed information to "not bump into obstructions". Your visual-spacial map of your home is part of your long-term memory which is completely accessible when you are asleep. You motorcortex is operating as it normally would, as well as your cerebellum … Basically, when you sleep the vast majority of your brain is still functioning as it normally would. Although, there are certain (few) parts of the brain that do seem to "shut down" during sleep. One of them is the prefrontal cortex, and the other is the hippocampus. The former is responsible for impulse control, judgement, logic and other "executive functions", so this is why (in general) people do dumb things while sleep walking. The latter is responsible for memory consolidation, so this is why people normally don't remember their episode. The reason sleep walking sounds so unbelievable is we think of the brain as in a state of off, but that is not the case at all. Our brains are always on, just in different states, controlled by neurotransmitters. If a person has some anomaly concerning a neurotransmitter during sleep, say serotonin or dopamine, then the stages of sleep can present in varying, abnormal ways, like sleep walking. This is very much an oversimplification, and I'm sure a neuroscientist could take it further, but I think this may be all that's needed to understand how sleep walkers don't "bump into" things.