Paraphrased, their questions gets to the following point:
What causes amnesia?
There are a lot of causes of amnesia.
Brain injury, for instance, causes many cases of amnesia. Whether it be blunt injury (as caused in accidents or falls…or physical assault) or a penetrating injury (such as a gunshot wound or stabbing), the brain tissue itself becomes injured. There is swelling of the brain and shearing of the neurons (the cells of the brain). Once the connection between cells is lost, signals get wonky and a whole host of signs and symptoms occur.
Some injuries also cause bleeding in the brain, which can be life threatening.
To sum up, brain injury can have temporary symptoms (such as short duration memory loss, headaches, and loss of consciousness) or long term and sometimes permanent symptoms (such as permanent memory loss, seizures, movement disorders, mood changes, and personality changes).
Excessive and chronic alcohol use can also lead to amnesia by affecting certain areas of the brain and by reducing the amount of available thiamine (a nutrient the body needs for good functioning and memory).
Other causes of amnesia include: Hypoglycemia (low blood sugar), hypoxia (lack of oxygen; can include carbon monoxide poisoning), multiple sclerosis, seizures, brain tumors, vascular disease (where the blood vessels are damaged and don’t work well to deliver oxygen), and encephalitis (inflammation of the brain tissue, caused by various bacteria and viruses). These conditions can and tend to affect the hippocampus, which is the part of the brain that keeps our memories.
Dementia and delirium (change in consciousness and awareness that flucutates and has many causes) also afffect memory, as do certain drugs, such as benzodiazepines.
Hippocampus in the brain:
Not to be confused with what the word means: (link)