The functioning of brain and body in sync with one another.
In the story, "Before I Go To Sleep" by S. J. Watson, the main character - Christine - is an amnesiac on two levels. She lacks the ability to recall memories as well as the ability to make new memories. Except for the fact that she can retain the memories she's made earlier in the day (episodic memory), she loses all of those memories while she sleeps. That is why her therapist has her keep a journal that he reminds her about everyday. That is the only way for her to truly "recall" things that have happened in her most recent past (the last few weeks since she started writing).
On the other hand, "Lock In" by John Scalzi, Chris is starting a new job as an FBI agent, but has to use a threep in order to function in the world. Twenty-five years before the start of this story there was a massive flu that swept through the world and caused a vast number to lose function in their body, except for their own mind. Each individual with this disease is trapped in a prison of flesh and bone. So, robot-like bodies, similar to C3PO in the Star Wars movies (threeps) houses the consciousness of these trapped individuals so that they can maneuver in the world of moving bodies. The disease is called Lock In. (One of the amazing parts of this story is that the gender of Chris is never mentioned. There are even two audiobooks - one version is read by Amber Benson and the other is read by Wil Wheaton.)
If I took both stories to represent the entire population then it seems like the Chris's of the world are getting a raw deal. Of course that's not the case. Diseases don't discriminate based on name, gender, race, identity, or anything at all. They attack and destroy. That is their only mission.
Both books handle extreme diseases, but they exist on opposite sides of the spectrum.
1. A person is aware of the world around them but cannot participate because of a nonfunctioning body.
- As is stated on the site for the National Organization for Rare Disorders: "Locked-in syndrome is a rare neurological disorder in which there is complete paralysis of all voluntary muscles except for the ones that control the movements of the eyes. Individuals with locked-in syndrome are conscious and awake, but have no ability to produce movements (outside of eye movement) or to speak."
2. A person lives and moves in the world, but has no platform for memory.
- On the Human Memory website (human-memory.net), it states: There are two main types of amnesia that can affect someone.
1. Anterograde Amnesia: The ability to memorize new things is impaired or lost because data does not transfer from the conscious short-term memory into permanent long-term memory.
2. Retrograde Amnesia: Pre-existing memories are lost to conscious recollection, beyond an ordinary degree of forgetfulness, even though they may be able to memorize new things that occur after the onset of amnesia.
- It would be almost impossible to truly love someone when you can't even remember them. A lot of life relies on making and retaining memories - without that, a person solely lives in the present with no ties holding them to any one person. Friends, family, loved ones, enemies - they're all the same because they're all strangers. I believe this would be difficult for the individual with amnesia, but a formidable and laborious road for those who were or want to be in the amnesiacs' life.
I wouldn't wish either of these diseases on anyone, but there are those who suffer from them. There are also those who live on the spectrum leading up to the Lock In disease. The best comparison for amnesia would probably be Alzheimer's because either a person has it or they don't.
The spectrum of diseases (in no particular order or exhaustive) leaning towards Lock In are:
1. ALS/Lou Gehrig's Disease: A disease that affects nerve cells in the brain and spinal cord. It literally translates to "no muscle nourishment," which means the muscles waste away. (Taken from the ALS Association website: alsa.org.)
2. Guillain Barré: The body's immune system attacks part of the peripheral nervous system. It may start as weakness in the legs, which can lead to weakness in the arms and chest. The most extreme version is almost total paralysis. (Taken from the National Institute of Health's National Institute of Neurological Disorders and Stroke: ninds.nih.gov.)
3. Early Parkinson's: This is a disease that signals a lack of control over your own body's movements. As stated online at healthline.com: It is a progressive disease of the central nervous system that is caused by a loss of cells in the area of the brain that produces dopamine. Dopamine is responsible for sending brain signals that control movement.
5. MS: A disease where your immune system attacks the material wrapped around and protecting your nerve fibers. This damages your nerves, which means the signals your brain sends don't transmit correctly through your body. (This description is taken from WebMD.)
6. Cerebral Palsy: Similar to Early Parkinson's, Cerebral Palsy (CP) affects the part of the brain that controls muscle movements, coordination, and balance. But the differences are that CP is a neurological disorder and it appears in infancy or early childhood. There is currently no cure for this disease. (Taken from the National Institute of Health's National Institute of Neurological Disorders and Stroke: ninds.nih.gov.)
The most comparable disease to amnesia is probably Alzheimer's. They both cause memory loss and are both incurable in certain cases. I explained above the two main types of amnesia, but the primary affect is only to the person's psychological state. Now let's look at how Alzheimer's affects an individual.
* Alzheimer's Disease: This is an irreversible, progressive brain disorder that slowly destroys memory and thinking skills, and eventually the ability to carry out even the simplest tasks. There is no cure and current medicine can only slow down the effects. Usually when someone is diagnosed, it is permanent. This disease affects the psychological, emotional, and physical condition of the person struggling with it. (Some of this was taken from the National Institute of Health's National Institute of Neurological Disorders and Stroke: ninds.nih.gov and the rest was taken from differencebetween.net.)
I would recommend you read both stories. I found them fascinating as well as great works of literature. They are both a great way to enjoy a world different from your own as well as learn more about the diseases affecting those around us.