Talking german in my sleep. is this common?

How can sleep talking be explained?

• This question is an extension of another Quora question that I find very interesting: What mechanisms underlie sleep talking and how is it different (in terms of involved brain areas) from talking when awake? At what age does sleep talking (also known as somniloquy http://en.wikipedia.org/wiki/Somniloquy) occur/start/become most frequent? Does sleep talking reflect maturation of speech-related brain areas (or perhaps general maturation of the brain)? Does sleep talking reflect acquisition of a (new) language and if so does it occur more frequent when adults learn a new language? What can sleep-talking reveal about differences in brain network of people that talk in their sleep versus people that don't talk in their sleep, or within a person nights without sleep talking as opposed to nights with sleep talking. What are other possible explanations for this parasomnia? Like for example its relation to stress, alcohol...

• Answer:

  I can't give detailed answers to each point, but maybe I can say something that points in the general direction of the answer.  One of the interesting things that neuroscientists have learned recently is that sleep can be localized to parts of the brain.  Most of the time when you are asleep your whole brain is asleep, but in some people some of the time, it happens that some parts of the brain are asleep while others are awake.  In particular it can happen that the frontal part of the brain, which plays a major role in high-level guidance of behavior, can be asleep while other parts such as the language system are awake.  I believe this phenomenon is the general explanation of parasomnias such as sleepwalking and talking in your sleep.  (It is also probably the explanation of hypnosis.) There is, however, at least one other possibility.  Normally when you are dreaming, your brain blocks the behavior you are dreaming about from causing movements of your body.  Sometimes, though, the movements partially escape from blockage.  This can cause thrashing of the limbs during a dream; it can also sometimes cause saying aloud the things you are dreaming about saying.