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Our future, our universe, and other weighty topics

Friday, September 30, 2016

How Could the Brain Store Long Sequences When Neurons Have No Linear Structure?

Scientists have never had any observational basis for making dogmatic statements asserting that long-term human memories are all stored in the brain. No scientist has ever done anything like reading a particular memory from particular neurons in a brain, nor has a scientist ever done anything like causing a particular memory in a human brain to be evoked when some part of the brain is electrically stimulated. There have been a few recent claims to have evoked memories in mice by optical stimulation of the brains of mice, but such claims are not well founded (for reasons discussed here). Nonetheless, neurologists and writers on the brain very commonly commit the intellectual sin of dogmatically proclaiming unfounded claims about the human brain, asserting that all human mental activity is due to brain activity. But other people have long suspected that the human mind is something more than just the brain, and humans have long tried to gather evidence to support such a claim.

One way of trying to substantiate the claim that the mind is more than the brain is to investigate anomalous psychic phenomena. If it can be found that the human mind is capable of paranormal experiences or talents that should be impossible for a brain to produce, that is evidence that the mind is something more than just the brain. Investigations into the paranormal have been highly successful in showing things we cannot explain by brain activity. Experimenters such as Professor Joseph Rhine accumulated very convincing evidence for extrasensory perception (ESP), as discussed here. Solid evidence has been gathered for near-death experiences.

Such evidence helps to substantiate the idea that there is something like a human soul that transcends the brain. But there is a very different way of trying to support the idea that the mind is more than a product of brain activity. This way involves looking not into anomalous activity of the human mind, but instead involves an analysis of perfectly normal, everyday activity of the human mind. The approach is as follows:
  1. Make a list of all the capabilities of the human mind, capabilities such as recall of childhood memories, and instant retrieval of a memory.
  2. Examine the physical capabilities of the human brain, and consider whether it is plausible to maintain that each of the capabilities of the human mind could be achieved by something such as the human brain.
  3. Whenever a shortfall is found – whenever we find some capability of the human mind that cannot be plausibly explained by the brain – mention this as evidence that the human mind involves something more than just the human brain.
In three previous posts, I put this strategy to work, and presented three arguments for believing that human memories cannot all be stored in the human brain. One argument was based on the apparent impossibility of the brain ever naturally developing all of the many encoding protocols it would need to store the many different things humans store as memories. The second argument was based on the apparent impossibility of explaining how the human brain could ever be able to instantly recall memories, if memories are stored in particular locations in the brain, because there would be no way for the brain to know or figure out where a memory was stored. The third argument was based on the fact that humans can remember 50-year old memories, but scientists have no plausible explanation for how the human brain can store memories for longer than a single year (partially because of rapid molecular turnover).

There is still still another argument that can be made along these lines, another argument based on a capability of the human mind that we cannot plausibly explain in terms of the human brain. This argument I will call the insertable sequential memories argument. I can concisely state the argument as follows: humans have the ability to store memories involving very long sequences, with an easy ability for insertion; but the human brain has no structural capability that can support any such ability, so some of our memories or ideas are probably stored or created in some mental reality that transcends the human brain.

First, let us consider the human ability to remember memories involving long sequences. An average person shows this ability by being able to remember the words and notes of many different songs. Each song is a particular sequence that must be remembered. You might think to yourself, “I don't know the words of many songs,” but if I were to have you browse though a list of the 500 most famous songs in history, you would find that you remembered the words and notes of lots of them. Of course, on the stage you might see something like a concert in which a singer sings from memory for 80 minutes. There are opera singers who have memorized various different roles in the operatic repertory, which may add up to many hours of words and notes they have memorized. In his prime years as an opera singer, Placido Domingo had at least 20 hours of opera roles he could sing upon demand (and would sometimes fill in for a sick singer, singing one of the many roles he knew by heart). Similarly, there are a number of Muslims who have memorized the entire Quran, a book of some 114 chapters or surahs.

We take this kind of sequential recall for granted, because this is the way we have always experienced memory working. Similarly, if we were able to exactly remember every word in each book we had read, we would take that for granted, and think it nothing special. But we must ask: does the brain have any type of structure that might allow such sequential recall to occur, if memories were all stored in the brain?

There is no such thing in the brain. The brain consists of billions of neurons, which are connected together. But there is a reason why the brain does not seem to have the right type of arrangement to allow for sequential recall of long sequences of information. The brain consists of neurons, and each neuron is connected to many other neurons. There is no “next” for a particular neuron. Neurons are not arranged in any type of chain-like structure that might support a recall of sequential memories.

Consider the physical way in which a book allows for a sequencing of information. Words are arranged in a linear order on a particular page. Also, the page order and binding of a book imposes a sequence on its contents, a sequential ordering we would not see if the pages were in a jumbled heap.

Or consider the DNA molecule. The DNA molecule is structured in a way that allows for a sequential storage of information. A DNA molecule is rather like an incredibly long and thin rope, in which a sequence of letters is written on the rope. Within the genetic code used by DNA, there is a particular sequence that acts as a “stop” signal, rather like a period in a sentence. With this physical structure, DNA allows for both a sequential storage of information and a demarcation of information.

But consider the human brain. There seem to be no physical characteristics that might allow for sequential storage of information. It seems that if you try to store information in the brain, it should be like tossing a set of alphabet blocks onto a giant heap in a junkyard.

I could schematically depict a set of neurons with a visual like the one below. The little circles represent individual neurons. The diagram greatly understates the number of connections between individual neurons.

Consider the recall of sequential information. Imagine you are trying to recall a series of words. We might imagine that individual parts of the sequence are stored in individual neurons – perhaps something a little like the schematic visual below.

But how could you recall the sequence in its correct order? Nerve cells are scattered throughout three dimensional space, with each neuron having many connections to other neurons. If information is stored in nerve cells, there would seem to be no way for a sequence to be stored in a way that would allow a sequential recall involving a long series, such as happens when an actor playing Hamlet recalls all of his many lines in the correct order. We can't imagine the brain simply going from one neuron to the “next” neuron to retrieve a sequence of information. This is because neurons don't exist in chains in which a particular neuron has a “next” neuron. Each neuron is connected to many other neurons.

Below we see a map of Dupont Circle in Washington D.C.

Once your car gets on Dupont Circle, there is no “next” place to go. You've reached an interchange in which there are 10 roads feeding out of the circular interchange. Similarly, in the photo below we see neurons. Each one of the parts coming out of the nerve cell is a path that can be traversed from this nerve cell. Such an arrangement should not offer any support for storing a sequence of information such as the lines in a play or the notes in a song. There's no “next” route leading from one neuron to the next neuron. Every neuron is like Dupont Circle, except that there are even more paths leading out of the neuron.

Now let's consider another aspect of human sequential memory: the fact that it is insertable. What this means is when we memorize a sequence, it is very easy to insert anywhere a new item in the sequence.

You can demonstrate this by trying a test such as this. Most Americans know the beginning of the song “America the Beautiful”

O beautiful, for spacious skies
For amber waves of grain

But what if we try to recall this sequential data with an insertion? Try memorizing the following variation, and see how long it takes to recall it while looking away from this page:

O beautiful, for spacious skies
For amber waves of tasty grain

This task is extremely easy. We have no problem inserting an item in the middle of something we have memorized. Similarly, if you (like most Americans) have memorized the famous line “we hold these truths to be self-evident: that all men are created equal,” then it is very easy to change that memory into something a little different, such as: “we hold these truths to be self-evident: that all men are created pretty much equal.”

So evidently humans can remember sequences, and it is quite easy for us to make an insertion anywhere in the sequence. But from a neurological standpoint, such a thing should be impossible. For let us imagine that there is some sequence of neurons that stores a sequential memory, ignoring the difficulty that a neuron has no “next” and so neurons do not seem to be suitable for storing a sequence. Then let us imagine we are inserting an item somewhere in the middle of this sequence. This should be as physically difficult as inserting a new steel link in the middle of a steel chain (or in the middle of a chain link fence). We cannot imagine that a new neuron gets created (in the middle of the sequence) to store the new word or words that are being inserted, because new neurons are not created for each new item inserted into our memories.

There is still one other problem in postulating that sequential memory is stored in the brain. This is the “end of sequence” problem. Try recalling the song “America the beautiful.” Typically your recall will end nice and neatly with the line “From sea to shining sea.” When we remember a sequence of items such as the words in a song, we remember only up until the end point of the sequence. But how could we possibly do that, if memories are stored in neurons? Given the organization of neurons in the brain, storing a memory in neurons would seem to be like tossing a bucket of letter blocks on to a mountainous heap of blocks containing letters, words and image fragments – not at all an arrangement that allows you to tell where the end point of a particular sequential memory is to be found. Or if we imagine instead an analogy of writing on a few vines in a thick Amazon-type jungle of very densely packed vines, the “end of sequence” problem still is there.

In short, if long-term memory were stored in the brain, it seems we shouldn't be able to remember long sequential memories, we should not be able to remember where such sequences end, and we shouldn't be able to easily insert new items anywhere in such a sequence – all things we are actually very capable of doing.

The points discussed here constitute another argument for believing that our long-term memories are not actually stored in the brain, but are stored in some greater mental reality that is merely related to the brain. An old-fashioned word for such a reality is “soul,” although it may be just as appropriate to use some other term. The argument discussed here is only one basis for postulating such a reality. Another argument is the reason discussed here: given the rapid molecular turnover in the brain (under which molecules are replaced every few weeks), there is no plausible and well-founded explanation for how the brain can be storing very long-term memories such as memories that last for 50 years. So we have very good reason for thinking that human memory involves something much more than just the brain.

There are many anomalies suggesting a similar conclusion, such as this astonishing account of a woman with only half a brain. It seems she can instantly state the day of week of any date you select in the past 18 years, without using any calculation. She also plays computer solitaire unusually fast. Such an anomaly is reminiscent of the research of John Lorber, who found many cases of almost normal functionality in people who had lost large fractions of their brains due to disease.

In the field of cosmology, scientists have long recognized that the known (regular matter and regular energy) is completely inadequate to account for the behavior of galaxies. So cosmologists have resorted to saying that there are completely mysterious things that play a large role in galactic dynamics: dark energy and dark matter. No one has any idea what these things are. It would seem that when it comes to explaining the human mind, we are in a rather similar situation. The reality that we know of (the brain) is quite insufficient to explain both extraordinary psychic experiences and even the ordinary reality of human memory. So we need to postulate something more than just the brain. If we followed the naming convention of the cosmologists, with their dark matter and dark energy, we might call this non-biological reality “the dark brain,” which would be a novel term for an idea that can be described with an old-fashioned term: a human soul.

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