In Dissociative Identity Disorder (DID), the experiences of individuals with the condition can be highly variable and complex. It is indeed possible for one alter to block out or have limited awareness of other alters for extended periods, sometimes even for years. This phenomenon is known as "amnesia barriers" or "amnesic walls" between alters.
DID is characterized by the presence of two or more distinct identities or personality states within one individual. These identities, also referred to as alters, have their own unique traits, memories, and ways of interacting with the world. Amnesia barriers between alters serve as a protective mechanism that helps the person with DID compartmentalize their experiences and cope with overwhelming or traumatic events.
When one alter takes control, it can be as if the others are in the background or completely unaware of what is happening during that time. The amnesia between alters can be so significant that each identity might have its own perception of time and experiences. For example, one alter may have memories up until a certain point, and another alter may pick up from that point without any awareness of what happened in between.
These amnesic barriers can be complex and may prevent different alters from communicating or being aware of each other's existence for extended periods. During these times, the host identity (the identity that is most often present and interacts with the outside world) may have no conscious knowledge of the other alters or even the presence of DID.
It is essential to note that DID is a complex and often misunderstood condition. While some media portrayals may exaggerate or misrepresent it, writing a novel that accurately and sensitively portrays DID requires thorough research and an understanding of the lived experiences of individuals with the disorder. If you intend to incorporate DID into your novel, I encourage you to approach the subject with empathy and respect, and consider consulting with individuals who have expertise or lived experience with dissociative disorders.