When a person is talking to himself/ herself or contemplating or dreaming while in sleep, then this type of communication is known as

A person talking to himself, contemplating, or dreaming in sleep is engaged in intra-personal communication.

This is communication within a single self, where one is both source and receiver of the message.

Inter-personal communication needs two people exchanging messages face to face, which a solitary self does not.

Inter-cultural communication occurs between people of different cultural backgrounds, again requiring others.

Inter-national communication moves across national borders between countries, far from private inner speech.

Self-talk, introspection and dreaming are classic instances of the mind conversing with itself.