I hope
le radical galoisen doesn't mind the title of this post (if he does, I'll change it!)
I've called him (
you) a student only because lrg has talked about school & college applications, and because his comment on the
Brain Rules fantasy school is an example of what the education world is concerned with these days, which is making connections between what you're reading now and what you've read before.
(I can't bring myself to use the words
prior knowledge. Sorry.)
The concept appears sound, observing from the case of a man (I forgot his name) whose hippocampus was almost totally destroyed in a viral attack, though he retained all of his skilled faculties from speaking very sophisticatedly to singing opera (though he had no personal memories).
Now of course, who wants to be the guinea pig?
lrg has jumped to what Medina describes as the main source of evidence for the existence of a 10-year "consolidation" rule (although
lrg is actually making a useful point about procedural memory - I'll get to that).
lrg is talking about a man named
H. M.Here's John Medina on H.M.:
But the rigor of Ebbinghaus gave future scientists their first real shot at mapping behavior onto a living brain. Then a 9-year-old boy was knocked off his bicycle, forever changing the way brain scientists thought about memory.
In his accident, H.M. suffered a severe head injury that left him with epileptic seizures. these seizures got worse with age, eventually culminating in one major seizure and 10 blackout periods every seven days. By his late 20s, H.M. was essentially dysfunctional, of potential great harm to himself, in need of drastic medical intervention.
The desperate family turned to famed neurosurgeon William Scoville, who decided that the problem lay within the brain's temporal lobe (the brain region roughly located behind your ears). Scoville excised the inner surface of this lobe on both sides of the brain. This experimental surgery greatly helped the epilepsy. It also left H.M. with a catastrophic memory loss. Since the day the surgery was completed, in 1953, H.M. has been unable to convert a new short-term memory into a long-term memory. He can meet you once and then an hour or two later meet you again, with absolutely no recall of the first visit.
He has lost the conversion ability Ebbinghaus so clearly described in his research more than 50 years before.
And here is Medina on the "conversion ability":
...our friend Ebbinghaus was the first to demonstrate the existence of two types of memory systems, a short form and a long form. He further demonstrated that repetition could convert one into the other under certain conditions. The process of converting short-term memory traces [through spaced repetition] to longer, sturdier forms is called consolidation.
[snip]
Memory may not be fixed at the moment of learning, but repetition, doled out in specifially timed intervals, is the fixative.
[snip]
Ebbinghaus showed the power of repetition in exhaustive detail almost 100 years ago. He even created "forgetting curves," which showed that a great deal of memory loss occurs in the first hour or two after initial exposure. He demonstrated that this loss could be lessened by deliberate repetitions.
In a nutshell -- and allowing for the fact that these processes are still not well understood --
- Memory consolidation means that a memory has moved from short term memory to long term memory.
- "Moving" from short term memory to long term memory means that a memory has moved from the hippocampus, in the temporal medial lobe, to the cortex.
- This process takes approximately 10 years.
We know this because H.M., whose hippocampus had been destroyed, lost all of his memories going back 11 years:
If you were to graph his memory, you would start out with a very high score and then, 11 years before his surgery, drop it to near zero, where it would remain forever.
What does that mean? If the hippocampus were involved in all memory abilities, its complete removal should destroy all memory abilities--wipe the memory clean. But it doesn't. The hippocampus is relevant to memory formation for more than a decade after the event was recruited for long-term storage. After that, the memory somehow makes it to another region, one not affected by H.M.'s brain losses, and as a result, H.M. an retrieve it. H.M., and patients like him, tell us the hippocampus holds on to a newly formed memory trace for years. Not days. Not months. Years. Even a decade or more. System consolidation, that process of transforming a labile memory into a durable one, can take years to complete. During that time, the memory is not stable.
Brain Rules by John Medina
On a slightly different subject,
lrg is actually talking about
procedural memory (
how to ride a bike memory), and I'm glad he brought that up. As he says, H.M.'s procedural memory was spared:
Investigators keen to argue for the separability of procedural memory had to look no further than the extensive investigations of H.M. In 1966, Miner reported that H.M. showed a completely normal learning curve on the mirror drawing task and, a little later, Corkin (1968) showed that H.M. learned at a comparable rate to normals on the pursuit rotor, bimanual, and tapping tasks. She also observed the development of “testing habits” whereby H.M. would become increasingly familiar with the testing procedures (knowing how to turn the equipment on, etc.) even though he denied any conscious recollection of having undertaken any of the tasks before. The selective preservation of procedural memory has now been observed in many amnesic patients but the purity of the preservation in H.M. has rarely been equalled.
Classic Cases in Neuropsychology
edited by Chris Code, Claus-W. Wallesch, Yves Joanette and Andre Roch Lecours
p. 342
I'm disappointed to see that John Medina doesn't appear to discuss procedural memory at all.
drat! I need someone like Medina to go through 50 years of research, read everything that's been discovered and/or hypothesized about the relationship between procedural, declarative, and semantic memory, and then explain it to me & everyone else.
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