I cannot figure out the meaning of this sentence:
There is a ground in between the voluntary and the involuntary occupied by expressions that were once learned but come to operate automatically without choice, or even despite choice, and typically without awareness.
For me as a non-native speaker it is kinda complicated. I guess the "ground" goes together with "occupied". However, it does not make any sense to me.
Could you help me with synonyms here to understand the first part of the sentence?