|Can too much learning lead to Alzheimer's?||Dr Piotr Wozniak,
|This article discusses the possibility that the Alzheimer's disease is triggered by memory overload in excessive learning or exposure to information-rich media. In that context, it also discusses the role of the Internet in promoting richer though less rigorous scientific exchange and cross-inspiration|
Recently, a user of SuperMemo wrote: I would like to know your comments about the article that claims that intense learning can lead to Alzheimer's: Does longer-term memory storage never become overloaded, and would such overload cause Alzheimer's disease and other dementia? (written by Robin P. Clarke, and published in "Medical Hypotheses").
To people familiar with the subject of senile dementia, the idea may seem absurd at first. After all, there has been quite a number of publications on the preventive impact of education in Alzheimer's. Upon closer scrutiny though, the quoted article includes lots of food for thought. At the same time, it is an excellent illustration of how the web can accelerate the progress of science. Inspiration can come not only from on-line claims that could not pass the peer-review test, but also from those that are riddled with errors, falsehoods, poor judgment, prejudice, bad intentions, or other departures from the purely scientific discourse.
Peer review vs. free speech
For over a century, peer-review science journals documented, disseminated, and perpetuated the word on the mainstream progress of human quest for new knowledge. Until recently, scientific publications were growing exponentially. Respected scientometrist Derek De Solla Price noticed that, as all good things in life, exponential growth cannot go on for ever. Indeed, the growth rate in the number of new publication has declined markedly. But Prof. Price, who died in 1983, could not have possibly predicted the new spontaneous growth of publishing on the web (unless he delved into the starry-eyed visions of Ted Nelson). Freed from the peer-review restrictions, web is now populated by scientific, semi-scientific, popular scientific, and pseudoscientific plethora of new research data, hypotheses, models, claims, and wild guesses. Without rigorous peer review, you never know what you get from the web. However, the Internet is now an unsurpassed source of new inspiration. For decades, peer review has been considered by many as a factor stifling free flow of ideas. Publish or perish principle makes scientists often move like wolves in a pack: few dare to step aside. Few want to struggle with peer review and delay publishing at the risk of perishing. No wonder then that peer review kills far out ideas. Continental drift theory proposed in 1910 by Alfred Wegener had to wait until the 1960s to be reborn as the theory of plate tectonics. Examples of ridicule in scientific community abound. As a result, many geniuses left the ranks of academics and moved to less frustrating activities like ... selling vegetables or free-lance free-thinking. Dr Robert Skoyles wrote "I witnessed many a bright student eager to prosper in the academic treadmill. They became deadwood preoccupied with marriage, mortgages and a pension". Having said the above, Skoyles set up his mouthpiece website jam-packed with interesting thoughts on neuroscience and far beyond [2011: the access to the original website was blocked in the Internet archive]. The web frees the genius and provides an open forum for the rebels. Many prominent scientists republish their materials on the net along a much wider volume of half-baked set of propositions, works in progress, word of mouth communications, rough sketches, etc. Others may prefer addressing a wider audience with popular scientific style which, interestingly, may often be a better conveyor of ideas even among his colleagues in the field. After all, many journals impose rigid formats, profile limitations, and other strict rules that enhance formal precision at the cost of the joy of discovery. Metaphoric tools of expression suffer on the way too. The net is full of errors and preposterous proposition; however, it is still a must-read for every mind looking for creative inspiration in any field. The freedom of expression produces a deluge of astrology, psychic "science", wellness advice, hate sites, creationism theories, super-learning, and what not. You will find a million articles on vegetarianism, but you will spend hours trying to sift those written with scientific data in mind, and without a religious or animal-rights bias. Even Google is helpless. Serious-looking articles sport a long list of references from prominent science journals and yet present out-of-this-world claims that have nothing to do with science. That is the side effect of free speech on the net. To the young folks, it may all be awfully confusing. However, to a trained eye, the net is all good news.
TruthRank as a global public review tool
In the wake of the PageRank system employed by Google, it is only a question of time before we see a TruthRank system where linking authors, using a hyperlink variable, testify to the degree of scientific reliability of quoted facts on linked websites. If reliable media link to a questionable material, their own TruthRank drops. Imagine searching Google by the degree of truth! Skeptics did not believe PageRank system would work. It works remarkably well. It made Google a star of search engines. TruthRank is the natural next step in the universal quest for the truth. [On March 1, 2004, Stanford University researchers published a formalization of this concept under the name TrustRank. In March 2005, Google registered the TrustRank trademark]
The quoted article on memory overload was rejected by Nature (and later Science and Lancet) and as such might be badly hit on the TruthRank side. Yet I will try to show that blocking its publication might have a negative side effect of suppressing the freedom of expression. It provides a new perspective, and new inspiration in reference to the hygiene of learning.
Evidence in favor
Glutamate and nitric oxide have been implicated in memory and nerve damage (e.g. nerve damage in multiple sclerosis). The neurological degeneration begins in the entorhinal cortex and spreads through the hippocampus, which, by its role in learning and by its neural capacity, is arguably most susceptible to memory overload. Several drugs have been developed to protect against neurological damage by glutamate over-excitation. Those drugs can, for example, slow down the damage occurring in the wake of a stroke. They work mainly by blocking NMDA receptors involved in the initial potentiation of synaptic connections in learning. Newer drugs are investigated in order to block nitric oxide synthase (i.e. the enzyme responsible for the production of nitric oxide in the course of synaptic transmission). It is true that the dentate gyrus, the site of neurogenesis discovered by Gage and Gould, is the relay station for sensory data arriving in the hippocampus. This exposes it to lots of glutamate able to produce neural damage. It is true that stress of information overload will potentiate this effect. Neural network models, in particular synaptic runaway in associative networks, provide a neat illustration of how the network might have behaved in conditions of overload. It is conceivable then that excessive learning could overload relay networks, produce synaptic runaway, and result in neurodegenerative damage through excess of excitatory neurotransmitters and other harmful byproducts of synaptic potentiation. It is conceivable that learning could do damage to your brain!
The quoted article includes quite a deal of flawed reasoning. Instead of postulating a hypothesis on the basis of evidence and looking for corroboration, Clarke starts off from confident claims that memory overload is the cause of Alzheimer's and later attempts to look for hypothetical explanations how his hypothesis might actually be implemented at the neural or molecular level. Author's view is vividly biased. The editors of Nature (back in 1995) had similar feelings, and their verdict on the article is understandable.
My main problem with the article is that if Robin P. Clarke was entirely right, you should soon expect an epidemic of Alzheimer's among users of SuperMemo. Considering that SuperMemo is already 15 years old, the epidemic should already be underway. The opposite seems to be true. Anecdotal evidence shows that early users of SuperMemo are today doing great or better as far as their mental capacity is concerned. They predominantly seem to occupy prominent positions in society. Naturally, I am aware that SuperMemo is more appealing for high-IQ individuals and the correlation may have multiple roots. With 100-120 minutes of SuperMemo per day, and a 20-year-long incurable learning addiction, I myself should have been struck with memory overload long ago. Although you can consider my opinions highly biased, I would give my right arm to vouch for learning as one of the best factors that would actually prevent senile dementia. Perhaps the trouble will begin only when users of SuperMemo start hitting the golden age of 80? Perhaps they will collapse into dementia in droves? I curiously look forward to that interesting milestone.
Here is a list of points I find most questionable in Robin P. Clarke's writing:
From chaos to the truth
Some people raised fears that the Internet will make it easier to spread pseudoscience, hatred or pornography. They were right. However, the solution should not be an outright suppression of zany or offensive material. It is true that it is extremely easy to hit a site deriding Islam as a "religion of hate and conflict". But it is equally easy to jump, with a few clicks, to a counter-site with anti-zionist material soaked with no less hate. In that sense, the Internet is less damaging than the printed matter where it is more customary to read lengthy (biased) materials cover to cover. Cover-to-cover implies a more stable imprint. The same refers to pseudoscience. If you use incremental reading to process fringe materials, you always run the risk of picking misguided inspiration. But in the sea of contradiction, the truth is the only survivor in the end. Let's try to reconcile the evidence for and against
Memory overload in learning
However much I have criticized the "memory overload" hypothesis above, one inspiration emerges. Overloading short-term memory circuits can indeed be unhealthy to their neural fabric. If runaway synaptic network model is true, if excess glutamate or nitric oxide are able to damage neurons, if the entorhinal-hippocampal relay is indeed subject to saturation, then running against the principle of mental hygiene could indeed result in the damage to the neural tissue. At the same time, well-paced and well-structured memory training could work as the best way of preventing Alzheimer's. This could work on two fronts: (1) the well-documented trophic effect on the nervous tissue, and (2) the systematic establishment of harmless neocortical long-term memories. Doing harm and good with the same factor (learning) do not need to be contradictory. The same happens to nearly all forms of exercise: you can over-train or apply a wrong training regimen to produce a negative effect.
Evolutionary reservations could be cut short by the observation that human populations (even as recently as in the 19th century) did not use to predominantly live to the ripe age of eighty; therefore, it could be cheaper to retain the present flawed memory overload handling than to perfect the system for the sake of longevity. Beyond active reproductive years, longevity does not translate to an evolutionary advantage. Even genetic predispositions related to APOE4 allele, APP, or presenilin genes would do little harm enough to stay afloat in the population. Especially that they seem to surface only in industrial societies where lipoprotein metabolism malfunction is rampant.
It seems plausible then that abuse of neural networks could lead to Alzheimer's while proper use of the same networks would lead to a long term benefit. In the same way as exercise leads to better health while immoderation in sports can be dangerous. Well-managed touch typing leads to high typing speeds while poorly-managed typing can equally well lead to repetitive strain injury. If there was to be a link between memory overload and AD pathology, using SuperMemo along the minimum information principle could be compared to moderate exercising, while cramming would be a form of running a marathon without preparation.
Whatever is said about the healthy brain may not necessarily apply to the optimum strategy for the treatment of Alzheimer's. On one hand, spaced repetition could help establish memories vital for survival. On the other, all forms of mental rest might also have a therapeutic value.
If we take all the above data into consideration then we could propose a few rules that could ensure your learning adventure does not go in a wrong direction:
Conclusion: Quality education will not cause memory overload because it produces compact representations (see: 20 rules). However, sloppy education in stressful conditions might go against the mental hygiene and indeed be harmful
Memetics in action
Once a meme virus of memory overload in AD is unleashed on the net it will propagate well in circles that oppose industrial growth, mass media culture, globalization, global transport, public schools, television, etc. It will also spread well among young folks who would just pick any excuse to do less learning. A counter meme of the therapeutic value of learning will propagate well among those involved in promoting learning tools or those who develop learning materials (here goes SuperMemo). When these memes clash, the truth is likely to see the light. The truth here may be analogous to the truth about the value of jogging. It can damage your knees. It can boost your glucocorticoids. Joggers smile less than walkers. Yet well-managed jogging might be the best known cardiovascular exercise.
Ignorance is always a good medium for false memes. Incremental reading loaded with contradiction helps resolve such ambiguities. The net is a wonderful breeding ground to promote psychic powers, astrology, reincarnation, UFO, tarot magic, dianetics, dowsing, neurolinguistic programming, clairvoyance, etc. However, there is no choice but the submission to free speech and competing ideas. The truth will come out in the end for those who care to see it.
Great sites for skeptics:
Year 2005 follow-up
More on potential damage caused by learning: http://www.urmc.rochester.edu/pr/news/story.cfm?id=930
Year 2011 follow-up
Robin Clarke submitted his reservations to this article. They can be found here: