Why the "A Memory Is Stored Throughout the Brain" Idea Makes Things Much Worse

No matter what form such an idea takes, the idea that the human brain stores memories creates the most gigantic difficulties, difficulties so bad that we should reject all claims that memories are stored in brains.  Let us look at two different forms of such an idea, and look at some of the difficulties that each form creates. 

The most common form of the idea that brains store memories is the idea that a memory is stored in one particular little spot of the brain, with each memory being stored in a different tiny spot.  Below are some (but not all) of the huge problems that such an idea creates:

(1) The spot selection problem. While computers have operating system algorithms for choosing a random storage spot,  a brain would seem to have no method or capability of choosing one small little storage spot for a memory to be placed. So if, for example,  we imagine that a brain placed a memory in storage spot number 263,432 out of 250,000 storage spots, we have the problem: why would that particular spot have been used to store the memory, and not some other spot? 

(2) The writing and encoding problem.  Once some spot had been selected for a memory to be written, something learned would have to be translated into neural states or synapse states and then written. There is no credible theory of how learned information or episodic memories could be translated into neural states or synapse states. There is no known mechanism in the brain for writing information. A computer has an operating system with formally designed encoding protocols such as the ASCII protocol and a protocol for converting decimal numbers into binary numbers. A brain has no such thing. A computer has a read-write head for writing information. The brain has no such thing. 

(3) The navigation problem.  Humans routinely display the ability to instantly recall learned information, given a name, date or image. So, for example, if you say "death of Lincoln," I will instantly be able to recite various facts about the death of Abraham Lincoln, such as that it occurred because John Wilkes Booth shot Lincoln through the back of his head at Ford's Theater in April, 1865.  If we believe that a memory is stored in some tiny little spot in the brain, such as storage spot 186,395 out of 250,000, then we have the problem: how was the brain able to instantly find that exact tiny spot where the memory was formed? This difficulty is a "show stopper" for all claims that a memory is stored in one exact spot of a brain, an insuperable difficulty.  We cannot get around such a difficulty by imagining that a brain uses the type of things that a book or a computer use to allow instant retrieval.  Books and computers use information addressing and indexes to allow instant access of a particular data item.  The brain has neither addressing nor indexes.  Unlike houses that have street addresses, neurons don't have neuron numbers or any other addressing system. Storing a memory in a brain would be like throwing a little 3" by 5" card into a giant swimming pool filled to the top with a million little 3" by 5" cards.  Just as it should take you ages to find a specific piece of information stored in such a swimming pool, it would take you ages to find in the brain some particular piece of learned information, if it was stored in one tiny spot, like a book stored in one spot on the shelves of a huge library.  

 

(4) The reading and decoding problem.  If a memory was stored in one particular spot, there would be the problem of how a memory could be read from that exact tiny spot. The brain seems to have nothing like a read mechanism.  Nor is there any known mechanism by which information that had been stored as neural states or synapse states could be translated into a thought that would appear in your mind. 

But there is another form of the idea that brains store memories.  There is the idea that the brain stores a memory throughout the brain, rather than writing the memory only in one little spot.  However, the difficulties in this idea are even worse than in the idea that the brain stores each memory in one specific spot. The idea that a memory is stored throughout the brain has the following difficulties:

(1) A greatly worsened writing and encoding problem. The idea that a memory is stored throughout the brain has the same writing and encoding problems mentioned above, except that now the problem is much worse. This is because now rather than just imagining that a memory is written in one tiny spot by a brain without any known writing mechanism, we must now imagine that such a brain manages to write all over itself each time that a memory is stored.  This would take much more time than writing to a single spot in the brain. Humans routinely show the ability to instantly form new memories,  an ability that neuroscientists cannot credibly explain. You only make that problem worse if you imagine that each time a memory is formed, the brain is writing to many different places rather than one. 

(2) A memory disassembly problem. The idea that a memory is stored throughout the brain creates a gigantic new problem that did not exist if you assume a memory is written to only one tiny spot: a memory disassembly problem. If you imagine that a memory is broken up into tiny pieces and stored throughout the brain,  then you have the problem that such a disassembly process would require additional time, making it all the more impossible to explain the wonder of instant memory formation. Similarly, it only takes a second for me to store a piece of paper by opening a book in my library and sticking the page inside the book; but if I have to cut up the page into twenty pieces and store the pieces in twenty books, that takes much longer. 

(3)  A memory reassembly problem. The idea that a memory is stored throughout the brain creates a gigantic new problem related to memory recall: a problem of reassembling the memory that had been stored in scattered pieces throughout the brain. If we imagine a brain with only one memory, such a thing does not seem so hard (the brain could just read throughout itself looking for memory pieces, and read them all up). But if we imagine many, many thousands of memories that had each been stored by storing pieces of individual memories throughout the brain, then such an assembly seems impossible to occur, no matter how long it would take.  

I can give an analogy. Suppose I am storing 1000 family photos through a scattered storage method. I take each of the thousand photos, cut them up into little pieces, and store each by putting them in different pages in the books that make up my large library. Now, suppose my wife comes and asks, "Please get me a picture of our trip to Los Angeles."  Retrieving that photo would be a nightmare.  I couldn't just get all the photo pieces by shaking each book in my library.  That's because the pieces of each photo would be mixed up with all the pieces of 1000 other photos.  Similarly, we can imagine no way in which a brain that has scattered pieces of each memory throughout itself could ever reassemble such pieces to produce a good recall of a particular memory.  And if it ever could do such a thing, such a recall would take very long lengths of time, and a recollection could never occur instantly.   

(4) A greatly worsened reading and decoding problem. The idea that a memory is stored throughout the brain has the same reading and decoding problems mentioned above, except that now the problem is much worse. This is because now rather than just imagining that a memory is read from one tiny spot by a brain without any known writing mechanism, we must now imagine that such a brain manages to read from all over itself each time that a memory is retrieved.  This would take much more time that reading from a single spot in the brain. Humans routinely show the ability to instantly retrieve new memories,  an ability that neuroscientists cannot credibly explain. You only make that problem worse if you imagine that each time a memory is recalled, the brain is reading from many different places rather than one.  

There was recently in the news an MIT press release story making the utterly unfounded claim that some research had shown that "a single memory is stored across many connected brain regions." What we have is another misleading claim about engrams from MIT, which for many years has been a notorious source of unfounded claims about neural memory storage.  In the 2018 post here I took a long look at how MIT memory researchers had repeatedly made grandiose but unfounded claims about memory research.  I showed that MIT researchers had again and again made grandiose claims based on shoddy poorly-designed rodent studies guilty of using way too small sample sizes.  The results proclaimed by such researchers are mainly false alarms, the type of false alarms that are very easy for a researcher to get when he uses fewer than 20 subjects per study group. 

The latest memory research announcement by MIT discusses research guilty of the same old shoddy research practices that MIT memory researchers have been guilty of for so many years.  Once again, when we read the scientific paper (which can be read here) we find that the researchers used way-too-small study group sizes, such as one group of only 7 mice, another group of another 9 mice, and another group of only 10 mice. If the scientists had acted like good experimental scientists and had done what is called a sample size calculation, they would have found out that such tiny study group sizes are utterly inadequate to produce a reliable result. But they did no such calculation. They confess in their paper, "No statistical methods were used to predetermine sample sizes."

The scientists fear-conditioned mice by electrically shocking them (this typically involves getting mice to learn there is one little area of a cage where the shocking will occur). The scientists then measured something in lots of different regions in the brain of a very small number of mice, and the scientists have somehow got the idea that some regions were involved in memory storage.  To test such suspicions they "optogenetically stimulated" mice to try to artificially create fear in the mice, zapping the little regions they thought were involved in storing a memory.  This "optogenetic stimulation" is a method of using light to zap the brain of a mouse. 

The thinking behind such strange zappings of mouse brains is that by zapping some little part of a mouse's brain, you can get a mouse to remember some fear memory formed when a mouse was zapped by stepping on an electrical plate.  The underlying theoretical assumption was wildly implausible. It was the idea that if a mouse has a particular memory stored in many brain regions, then you can get the mouse to re-experience that memory by stimulating only one of those regions.  Such an idea makes no sense. It's kind of like thinking that I would get Tom Brady to throw a pass by sticking a sewing needle in his arm, stimulating one of the many muscles he uses in throwing a pass.  

Conclusions about whether the fear memory was recalled were based on a poor low-reliability technique that neuroscientists have long used: a judgment about whether so-called "freezing behavior" occurred (such behavior being defined as mere inactivity). The underlying assumption is that mice freeze when afraid, and that you can judge if a mouse is recalling a fear memory by looking for an instant of non-movement in which a mouse may be "freezing in fear." Given the start-stop, helter-skelter way in which mice move, any judgment about whether a mouse froze is going to be a subjective, unreliable judgment. So there is too much of a possibility of observational bias here, one in which an observer subjectively reports the effect he is hoping to find. Similarly, you might subjectively report that your goldfish in a goldfish bowl tends to move towards you when you are looking into the bowl, but that would probably tell us more about your desire to see something than about the goldfish. The idea that mice freeze when terrified isn't even a very sound one.  I have seen  dozens of mice flee when scared by a human, but I never once seen a mouse freeze when suddenly scared by the presence of a human. 

There is a very reliable way to measure fear in mice: you measure the mouse's heart rate, which undergoes a very sharp spike in mice when they are afraid. Our neuoroscientists senselessly continue to use unreliable subjective judgments about "freezing behavior" to try to measure fear in rodents, rather than sensibly using reliable measurements of heart rate spikes in rodents.  Being guilty of this flaw, the new MIT study has provided no reliable evidence about whether or not the mice remembered fear when parts of their brains were zapped. 

Moreover, when "freezing" (simple non-movement) occurred in the mice, the "freezing effect" could have been produced not by a recall of fearful memories, but by the very fact the energy was being transmitted into the brain of the mice. Imagine you are running along, and suddenly a scientist switches on some weird thing that causes some energy to pour into your brain. This all by itself might cause you to stop, even if it didn't cause you to recall some memory that caused you to stop. What could have been going on in the mice was just a kind of pausing effect caused by a novel stimulus rather than a recalled fear effect. A science paper says that it is possible to induce freezing in rodents by stimulating a wide variety of regions. It says, "It is possible to induce freezing by activating a variety of brain areas and projections, including the hippocampus (Liu et al., 2012), lateral, basal and central amygdala (Ciocchi et al., 2010); Johansen et al., 2010;  Gore et al., 2015a), periaqueductal gray (Tovote et al., 2016), motor and primary sensory cortices (Kass et al., 2013), prefrontal projections (Rajasethupathy et al., 2015) and retrosplenial cortex (Cowansage et al., 2014).”

Neither the paper nor its supplementary information contains any  mention of a blinding protocol, other than the bare statement that "all behavior experiments were collected and analyzed blind to experimental group."  Unless a paper has a detailed discussion of  how an effective blinding protocol was implemented (one that really achieves a blinding effect to prevent observer bias), we should assume that no effective blinding protocol was implemented.  For example, if you had one group of 7 mice with optogenetic wires attached to their brains, and another group of control mice with no such wires, anyone would be able to tell which group was the group that was hoped would show more "freezing" behavior (even if those judging how much the mice froze were not specifically told which group was which).  So some method that can technically be referred to as "blind" may not be blind at all because of a lack of an effective protocol. Whenever any paper claims a blinding protocol but fails to specify how an effective protocol was achieved,  we should assume that no effective methods of blinding were used (a severe defect in an experiment). 

Being guilty of quite a few serious methodological flaws (primarily the use of way-too-small study group sizes), the new MIT study has produced no robust evidence that memories are stored in the brains of mice, and no robust evidence that a memory is stored in many different regions of the brains rather than in some particular spot. According to the paper here, "Quality research practice requires both testing statistical significance and reporting effect size." But the new MIT paper reports no effect size. That is what goes on when shoddy experimental research practices have been followed, such as using way-too-small study group sizes. 

In this paper here we have a discussion of the absurd technique most commonly used to measure fear in rodents:

"In mice, freezing is a common and easily measured response used as an index of fear conditioning (Blanchard and Blanchard 1988; Graef 1994). Fanselow (1990) and Paylor et al. (1994) define freezing as the absence of any movement except for respiratory-related movements. Freezing behavior is measured by direct observation, scoring an animal as either freezing or active per interval of time, usually every 5–10 sec (Fanselow 1990; Paylor et al. 1994) or measuring freezing duration with a stopwatch (Phillips and Le Doux 1992)."

The technique discussed above measures only mouse inactivity, which will vary randomly. There is no sound basis for calling such a measurement a measurement of "freezing behavior." If I take 10 snapshots of a mouse per minute, that show the mouse not moving in three of those snapshots, that is no reason for thinking that the mouse was afraid when three of those ten snapshots were taken.  What is occurring these days among cognitive neuroscientists is deceptive labeling of mouse inactivity measurement. Graphs that should be labeled "mouse inactivity (%") are being misleadingly labeled "mouse freezing (%)."  The term "freezing" should never be used unless a sudden stopping of traversal was observed.