Post by MaybeNever on Oct 22, 2011 19:54:05 GMT -5
As Vene said, potentiation represents a part of it, but prevailing thought is that it's actually a fairly major part. Synaptic structure is another factor, although this is related to potentiation. Unfortunately, the big picture of how memories are formed and stored is horribly unclear for many of the same reasons from before: it's very hard to study a living brain in enough detail to see exactly what's going on, or to get reference points. The fact that the brain is always forming new memories and learning new things, literally second by second, also complicates the problem.
Memory formation is somehow related to the hippocampus, a fairly primitive brain structure (which points to the significance of learning as an evolutionary adaption in animals). Importantly, individuals with severe damage to the hippocampus frequently develop anterograde amnesia - the inability to form new memories, although old memories are preserved. It is in part because of the hippocampus's role in potentiation that it is believed to be such a major factor in memory storage.
Curiously, individuals with injuries resulting in or necessitating neural ablation - the removal of sections of the brain - do not appear to suffer the loss of memories as a result of the damage. When retrograde amnesia, or the loss of old memories, does occur, it is overwhelmingly recent memories that are lost. For example, a person in a car accident will lose memories of the accident and perhaps a short time before, but not memories from an hour or a week before. Because this is experienced even by people who are not injured in such events, it is unlikely that this kind of amnesia is reflective of brain damage. One theory to explain this localization of memory loss is that older memories exist in a distributed, sub-cortical fashion, i.e. with extreme redundancy across the brain. Potentiation would help explain this, but the exact mechanism remains a mystery.
Of course, movie-style retrograde amnesia does sometimes occur. One condition, called Korsakov's Syndrome (I've also see it spelled Korsakoff's), appears to arise from chronic malnutrition, specificially a B1 deficiency, and is most commonly seen in chronic alcoholics. The exact role B1 plays in the maintenance of memories is, naturally, not really clear. In Korsakov's, the individual can lose decades. Oliver Sacks, for instance, wrote about a 60-ish patient who lost roughly forty years of his life. He was further unable to form new memories, such that Sacks had to introduce himself anew to the patient every time he left the room or patient's attention wandered. You can find the account in Sacks's The Man Who Thought His Wife Was A Hat.
Lithp, you're in the unfortunate position of asking the Big Questions of a field that's barely started to scratch the surface. A lot of the answers you'll get back are going to have significant components of "nobody knows" to them.
"Great Britain's two most senior military officers added to the uneasiness. [...] Lord Wolseley, Adjutant General, thought that it might be possible for an enemy to invade without waiters and pastrycooks." -Robert K. Massie, Dreadnought