Why do people with amnesia forget things like the names of people, or past memories; but they don’t forget how to speak or how to count and do maths?
In: Biology
There are two kinds of long-term human memory: explicit (or declarative), and implicit, and they are stored in entirely different parts of the brain. Explicit memories include episodic memories (specific personal experiences) and semantic memories (factual information). Episodic memories, and explicit memories in general, are most commonly affected by amnesia.
Implicit memories, including procedular memories (knowledge of how to perform tasks without conscious awareness of previous experiences), are stored in different parts of the brain from explicit memories. Amnesia is usually associated with damage to the hippocampus, which is heavily involved with explicit memories but not particularly involved with implicit memories. However, extremely heavy brain damage could lead to the loss of both kinds of memory.
Sources: [https://en.wikipedia.org/wiki/Implicit_memory](https://en.wikipedia.org/wiki/Implicit_memory#Multiple_memory_system) , [https://en.wikipedia.org/wiki/Explicit_memory](https://en.wikipedia.org/wiki/Explicit_memory#Normal_brain_function)
Different activities are handled by different parts of the brain. Amnesiacs have typically suffered damage to the part of the brain tasked with storing/retrieving event and object memory – specific things and places and events.
That area doesn’t handle “operative” memory like speech, logic, or motor skills, so the unlucky patient is usually perfectly articulate and coordinated, they just can’t remember anything. There are multiple cases of severe amnesiacs still knowing how to play instruments or do other complex tasks, but with no knowledge of how they learned such a skill.
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