Due to coming together of what does the dream arise?

Buddha explains how world came to be by saying eye and forms come together to create eye consciousness. Coming together of eye, forms and eye-consciousness created contact. Contact lead to feelings which lead to birth , death and suffering. Same applies to ear , nose , tongue , mind. But when we sleep the eyes are shut yet we see the dream. How is that possible ? In that dream I am able to see, hear , touch and feel. Due to which contact in this real world am I able to live the dreams ? My question is : due to coming together of which internal and external senses does the dream arise ?