We actually have a pretty decent understanding of what all the parts of the brain are involved in (though what regions actually serve what functions varies slightly from person to person). Most of the brain is used for information relay and processing various forms of information.
With memory loss, they are almost certainly completely lost or heavily altered. Memory "retrieval" typically is achieved by prompting the brain to take what bits of information it still has about something and doing some heavy filling of the gaps, which results in false memories that can seem very vivid, and people can be very confident those false memories actually happened. It doesn't even take much time for there to be missing pieces that need to be filled in upon retrieval; our memories are surprisingly inaccurate overall, at least for details of episodic memories.
We actually have a pretty decent understanding of what all the parts of the brain are involved in (though what regions actually serve what functions varies slightly from person to person). Most of the brain is used for information relay and processing various forms of information.
With memory loss, they are almost certainly completely lost or heavily altered. Memory "retrieval" typically is achieved by prompting the brain to take what bits of information it still has about something and doing some heavy filling of the gaps, which results in false memories that can seem very vivid, and people can be very confident those false memories actually happened. It doesn't even take much time for there to be missing pieces that need to be filled in upon retrieval; our memories are surprisingly inaccurate overall, at least for details of episodic memories.