Complex sentence: The episodic content of autobiographical memories is predominantly encoded in the form of visual images and if the ability to generate visual images is compromised or lost then access to specific details of the past held in episodic images is lost as well.
Split into simpler sentences: The episodic content of autobiographical memories is predominantly encoded in the form of visual images. If the ability to generate visual images is compromised or lost then access to specific details of the past held in episodic images is lost as well.