Types of Memory: When is 'Amnesia' Applicable?

"Clive's passionate relationship with his wife Deborah, a relationship that began before his encephalitis, and one that centers in part on their shared love for music, has engraved itself in him—in areas of his brain unaffected by the encephalitis—so deeply that his amnesia, the most severe amnesia ever recorded, cannot eradicate it."

- A Neurologist's Notebook: The Abyss

I found the passage above to best exemplify some of the strengths and weaknesses of Oliver Sacks' writing. The main goal of this line is seems to be to evoke a thought in the reader's head: "not even most severe form of amnesia ever recorded can deny this man love for his wife and for music --how beautiful." (That's the strength)


It is important and interesting to note that Sacks does mention between the dashes that the Clive's encephalitis did not affect those areas any of those areas of his brain, yet he deliberately maintains this characterization for the sake of the narrative. Logically, the sentence is like saying that Clive miraculously maintained the sort of memory of love for his wife through the most severe of ear infections, or really, any unrelated condition. --The reason I find this worth noting as a weakness is because rather than imply a undescriptive quantitative ('deepest') aspect of memory for the sake of the narrative, Sacks could emphasize the qualitative one, and we would end up with a more faithful perspective on what is going on in the brain and why the memory of their relationship was not forgotten along with other aspects of his life. He does this by mentioning the experiment with the needle-handshake and distinguishing emotional memory from other types of memory, but doesn't give us the same coherent idea of neurological underpinnings as he does in other writings. I'm looking forward to LeDoux's upcoming chapter on emotion, which will likely shed more light and detail on this aspect of memory.

Another topic I found interesting was Sacks' discussion of procedural memory with regard to Clive's retained ability to retain piano-playing skills:

"The basis of procedural or implicit memory is less easy to define, but it certainly involves larger and more primitive parts of the brain—subcortical structures like the basal ganglia and cerebellum and their many connections to each other and to the cerebral cortex. The size and variety of these systems guarantee the robustness of procedural memory and the fact that, unlike episodic memory, procedural memory can remain largely intact even in the face of extensive damage to the hippocampi and medial temporal-lobe structures."

I was glad Sacks added this much into the reading, but it left me with a lot more questions. We know that working memory proccesses are different from long-term memory processes which involve conversion via the hippocampi and also the 'reconstruction' process involved in retrieving episodic memories. We've seen in the case of patients like H.M., working memory is stable enough so they can partake in short tasks or have short conversations (like the Lost Mariner, but unlike Clive repeatedly thinking "I'm wake. Now I'm awake. No, now i'm awake").

Are there case-studies that show examples of 'procedural memory amnesia'? Is this because procedural memory completely different in that it does not require a highly specialized system for the reconstruction process? Or is there a way to produce amnesia of procedural memory? I look forward to gaining a better idea of this system...

One point I am unclear on is to what degree procedural memories are not physical. I think cracking an egg into a pan involves procedural memory, but remembering a routinely used omlet recipe might also be immune from retrograde amnesia, though it is difficult to measure since a person with retrograde amnesia typically will still know what an 'omlet' is. No one would argue that knowledge of vocabulary would fall into the same system as the procedural memories assumed to be in subcortical structures such as the cerebrellum, but on a theoretical basis, their coding or representation may be similar, or at least both different from episodic memory in that the content of the past memories cannot simply be split from the ability to learn new memories... Again, looking forward to reading about studies on language disorders and whether or not cases have been found where a patient has retrograde amnesia of vocabulary, or retains loses ability to learn new words, but maintains the past words. This at first thought appears unlikely, though it would help us further divide types of memory and gain clarity on how memories are represented through the brain.