Intelligent husks store their memories in two places, their brain and their heart. Though the brain is where the most important memories are located as well as everything else. The most important memories are referred to as core memories, and they are what makes an intelligent husk themselves. That includes likes, dislikes, emotions, important events or moments…everything that makes them them.
While the brain is the main holder of memories, the heart works in a similar way. But rather than holding everything that makes an intelligent husk an individual, it holds copies of various things and memories. There are copies of some important memories, personal things such as bits and pieces of interests, personal history and personality. Really enough just to keep the husk functioning if something were to happen to the original head. It’s sorta like recording bits of a show. You have an idea what's going on, but no where near enough information to put all the pieces together. Though the loss of the intelligent husk’s original head can be disastrous.
The places that the memories are stored are the reason that a husk has to be killed a certain way. Their heart must be cut out and they must be decapitated before everything is set on fire. This guarantees that the husk is destroyed in their entirety and that they have no chance of regeneration. Because even without the head and the core memories, there is enough stored in the heart that the husk can function as a separate entity away from the head, get up after decapitation, and then go find and take a head to replace the one that’s been lost.
Replacement heads are where another problem lies for an intelligent husk. Normal elementals don’t have memories stored in their hearts, everything is stored in the head. So killing an elemental by any means is permanent. When an intelligent steals an elementals head, they not only regain the main control for their body and a place to store any memories that had been copied to the heart but to also make new core memories. But the elemental’s head still contains all of the memories of that Individual before they died, so now there’s all of those memories and experiences in there as well as the husks own. This can lead to the husk confusing their original memories with the memories of the replacement head’s. The longer the the husk has this replacement head the worse it gets.
Not only will the husk confuse their own memories that they brought with them with the replacements head, they are missing key bits of their own memories. Thus confusing and disorienting them more. As time goes on the husk may forget facts about themselves (like how Ashitaka can’t remember what his name is or much of anything before he lost his original head). By that point an intelligent husk with a replacement head are generally harmless because they’re so confused. They can’t remember who they really are or which memories is who’s, and they become more worried about figuring out who they were rather then wreaking havoc.