Jeremy Allen
I began with some simple questions about how spaced repetition works and what the documented benefits are. I ended up listening to J. Krishnamurti and David Bohm talk about the mind works and what the “I” in the brain really is. I have read a number of books over the years, like Barbara Oakley’s book, “A Mind For Numbers”, that discuss various strategies for learning new and challenging topics. The general consensus seems to be that spaced repetition works and the general thesis about the brain’s forgetting curve is, at a minimum, anecdotally correct. It makes sense at some logical level given how the brain tends to prune unused connections. This led to my next line of inquiry, specifically, when we perform spaced repetition consistently what are we actually doing in our brain? What effect does this have? What can physical science observe about how it works.
The hippocampus is a spiral shaped part of the brain that is important in the consolidation of short term memory to long-term memory. It also plays an important role in spatial memory, which is important to help humans navigate the physical world. This is also one of the first impacted regions of the brain in Alzheimer’s disease and other forms of dementia. The hippocampus also happens to be one of the few places in the adult brain where neurogenesis can occur. One of the often cited papers on the hippocampus is about that of British taxi drivers. This is important as it shows there can be plastic changes in the adult brain. It also shows that taxi drivers, who have to memorize a lot of geo-spatial facts grow their grey matter here. So, there is a trade off here about how you use the hippocampus. The taxi drivers actually did worse on tasks around learning new unfamiliar visual-spatial information such as navigating a new town. What we don’t know is if, say, a taxi driver reliably encoded both their navigation information and other types of information that would impact the anterior region more. Is there a hard structural limit on the hippocampus? What impact might that have. There is only so much space and energy in the skull after all. What happens if we are a consistent spaced repetition practitioner and not say, a taxi driver that still had to actually memorize information?
It turns out engineering broadly, including software and security engineering, heavily rely on the anterior region of the hippocampus. If you are an engineer and always felt you struggled with navigation, now you know why. Your brain has been prioritizing the anterior region of the hippocampus so you can do engineering tasks. Real estate in the brain is limited so the brain does not retain all of the new neurons that get created in the hippocampus. The goal with spaced repetition is to generally keep fact sets in the hippocampus long enough to train them into the long term storage of our brain, the neocortex. This lead to my next interesting line of inquiry around if the brain actually gets tired and what role sleep plays in these processes around the hippocampus, neocortex, the brain’s energy system, and sleep. How do the memories actually get to the neocortex?
What happens when we close our little eyes and fall asleep?