Claims that brains store memories and produce thinking are not well-established scientific facts, but mere speech customs of neuroscientists who belong to a belief community as dogmatic as the communities of organized religions. Such neuroscientists tend to pay shockingly little attention to the implications of the low-level findings neuroscientists have made about brains. Replacing its proteins at a rate of about 3% every day, brains are neither stable enough nor fast enough to explain things such as the instant accurate recall of 50-year-old memories.
People who write about the brain frequently use a trick to make you think that brains are very fast. Such people will tell you that brain signals can travel up to 100 meters per second. But this is the speed when signals pass through the fastest tiny parts of the brain. This is the speed of signals when they travel through what is called a myelinated axon. The mylein sheath around the axon (with a white color) is what makes it so fast. It is interesting that the site here says, "The axons of grey matter are not heavily myelinated, unlike white matter, which contains a high concentration of myelin." Axons without much of a myelin sheath are believed to transmit brain signals about 5 times slower. According to the diagram here, signals travel across myelinated axons at speeds between about 20 and 120 meters per second (depending on the thickness of the axon), and signals travel between unmyelinated axons between about 5 and 25 meters per second.
But citing a speed of meters per second for the speed of a brain signal is very misleading. It is as misleading as saying that you can drive through New York City very quickly, on the grounds that you can reach a speed of 30 or 40 miles per hour. Considering only such a maximum speed is misleading, because when you travel through New York City, you will be slowed down by many red lights. Similarly, while some microscopic parts of the brain allow a fast transmission of signals, there are very many microscopic parts of the brain which very much slow down brain signals. You might figuratively put it this way: the brain has billions of red lights all over the place, and each of those spots will slow down the speed of a brain signal. So while the maximum speed of a brain signal during any millionth of a second may be as high as meters per second, the average speed of a brain signal is much, much slower, something on the order of one centimeter per second or slower.
The schematic diagram below illustrates the point. We see a diagram of a neuron, one of the billions of cells that make up the brain. Protruding from the main part of the neuron are dendrites. The transmission of signals through dendrites is slow, so next to the dendrites is a snail icon representing how slow such units are. According to neuroscientist Nikolaos C Aggelopoulos, there is an estimate of 0.5 meters per second for the speed of nerve transmission across dendrites (see here for a similar estimate). That is a speed 200 times slower than the nerve transmission speed commonly quoted for myelinated axons. Such a speed bump seems more important when we consider a quote by UCLA neurophysicist Mayank Mehta: "Dendrites make up more than 90 percent of neural tissue." Given such a percentage, and such a conduction speed across dendrites, it would seem that the average transmission speed of a brain must be only a very small fraction of the meters-per-second transmission in axons.
In the diagram above, we see a chain-like unit in the middle. That part is a myelinated axon, which can transmit a brain signal quickly. So I have put a rabbit icon next to that part, to indicate the relatively speedy signal transmission of that part.
The bottom right part of the diagram shows some axon terminals that have synapses at their ends. Synapses are a serious "speed bump" for signal transmission in a brain. So I have put a snail icon at the bottom right of the diagram to indicate that slowness.
How much of a "speed bump" are synapses? There are two types of synapses: slow chemical synapses and relatively fast electrical synapses. The parts of the brain allegedly involved in thought and memory have almost entirely chemical synapses. (The sources here and here and here and here and here refer to electrical synapses as "rare." The neurosurgeon Jeffrey Schweitzer refers here to electrical synapses as "rare." The paper here tells us on page 401 that electrical synapses -- also called gap junctions -- have only "been described very rarely" in the neocortex of the brain. This paper says that electrical synapses are a "small minority of synapses in the brain.")
We know of a reason why transmission of a nerve signal across chemical synapses should be relatively sluggish. When a nerve signal comes to the head of a chemical synapse, it can no longer travel across the synapse electrically. It must travel by neurotransmitter molecules diffusing across the gap of the synapse. This is much, much slower than what goes on in an axon.
There is a scientific term used for the delay caused when a nerve signal travels across a synapse. The delay is called the synaptic delay. According to this 1965 scientific paper, most synaptic delays are about .5 milliseconds, but there are also quite a few as long as 2 to 4 milliseconds. A more recent (and probably more reliable) estimate was made in a 2000 paper studying the prefrontal monkey cortex. That paper says, "the synaptic delay, estimated from the y-axis intercepts of the linear regressions, was 2.29" milliseconds. It is very important to realize that this synaptic delay is not the total delay caused by a nerve signal as it passes across different synapses. The synaptic delay is the delay caused each and every time that the nerve signal passes across a synapse.
Such a delay may not seem like too much of a speed bump. But consider just how many such "synaptic delays" would have to occur for a brain signal to travel from one region of the brain to another. It has been estimated that the brain contains 100 trillion synapses (a neuron may have thousands of them). So it would seem that for a neural signal to travel from one part of the brain to another part of the brain that is a distance away only 5% or 10% of the length of the brain, that such a signal would have to endure many thousands of such "synaptic delays" resulting in a cumulative synaptic delay of quite a few seconds of time.
The problem is that we know humans can instantly recall obscure pieces of information, and instantly do complex calculations. We see this on TV shows such as Jeopardy, where people again and again give correct answers after a delay of only about 1 second when being presented surprise pieces of very obscure information such as "Works of this Nobel Prize winner include Song of Solomon and Beloved," and "This was the city where King Louis XIV died." It is well known that certain people (some called autistic savants) can do things like instantly tell you the day of the week for any day you select in the century. There are some math calculation prodigies who can actually calculate faster than any person using a hand calculator. It is impossible to account for such speed under the theory that your brain stores your memories and your brain produces your thoughts.
Here are all the time factors we would need to account for under a theory of neural memory storage:
(1) The time needed to find where a memory was in the brain. Since the brain has no indexing system, no addressing system, no coordinate system, and no position notation system, we can only assume that this would be a very long time, like the time required to find a needle in a haystack.
(2) The time needed for an encoded memory stored neurally to be decoded and translated into a thought ending up in your mind. That would take quite a while. We know that it takes quite a while (many seconds) for the brain to do the only type of decoding known to occur in it, the decoding of genetic information stored in DNA (a type of decoding incomparably simpler than the fantastically complex decoding that would be needed to decode some memory encoded as neural states or synapse states).
(3) The time needed for signals to travel around in your brain. That would take quite a few seconds, because signals would have to travel across thousands of synapses, each of which would produce a synaptic delay (and also thousands of dendrites that would slow down things).
In short, there are multiple redundant reasons why you would never be able to recall something instantly if memories were stored in your brain. The slowness of brain signals also means very rapid thinking cannot be a brain effect. An example of rapid thinking is that when asked in a competition what was 869,463,853 times 73, Neelakantha Bhanu Prakash correctly gave the answer of 63,470,861,269 in only 26 seconds. Similarly, Scott Flansburg added a randomly selected two-digit number (38) to itself 36 times, in only 15 seconds. Such calculations could never occur that quickly if it were performed by a brain with "red lights all over the place."
I'll give an example of a type of question no one would be able to answer in a short time if recall and thinking were the products of the brain. Consider the question: which Broadway composer may remind you of a children's TV show? Many people my age can answer such a question fairly quickly. But think of how much mental activity it involves:
(1) Scanning through your very diverse memories of the names of Broadway composers.
(2) Scanning through your very diverse memories of the names of children's TV shows.
(3) Looking for some kind of fuzzy match (not an exact match) between the two different groups of items.
The correct answer is: Rodgers, because the great Broadway composer Richard Rodgers has a name sound-matching the name in the once-famous children's TV show "Mr. Roger's Neighborhood." It would take you hours or days to answer such a question if you had to use slow synapses and slow dendrites to solve it, searching through a brain without any indexing system or coordinate system; but many people my age could answer such a question in a few seconds.
It would be very incorrect to suggest that when humans remember, they always only use some memory acquired at one time. For example, ask a man to describe the difference between modern living and ancient living, and someone might quickly say something like this:
"We use cars not chariots, and fight with armored divisions not legions. We message with emails not carrier pigeons. We read using smartphones not scrolls, and wear trousers not togas. We pray to Jesus not Jupiter. We are paid with direct deposits, not coins."
Such a simple response could easily occur in a few seconds, but if brains store our memories, it would require finding, retrieving, understanding and intelligently using information stored in a dozen different little spots in a brain (a brain without an addressing system or indexing allowing fast retrieval). So it would take a long time, and could never occur instantly.
A scientific paper suggests that neuroscientists are not paying proper attention to signal delays when calculating the speed of brain signals. It says, "Despite their inevitable physiological significance in living systems, propagation delays are usually overlooked in mathematical models, presumably to avoid further complexity." That's as silly as calculating the time it would take you to drive through the middle of New York City without taking into account the time spent at traffic lights.
"The spread of activity through cortical circuits has been studied in experiments by means of electrical registrations and optical imaging [1–3], and high-density microelectrode arrays . Experiments show slow propagation of an ictal wavefront and fast spread of discharges behind the front  . The ictal wavefront progresses through the cortical area at a pace of < 1 mm/s, which is consistent with propagation speeds measured with electrodes and imaging in brain slice models [1, 2, 6–9] and in vivo (0.6 mm/s in  with two-photon microscope and 0.5 mm/s in  with widefield imaging in mouse neocortex)."
There is no particular reason for thinking that information-transmitting brain signals in the cortex would travel very many times faster than this low speed of about 1 millimeter per second. The surface area of the brain is about 2500 square centimeters (about 2,500,000 square millimeters), about the size of a pillow case. The brain can fit in the skull because of extensive folding, rather like a pillow case folded up to fit inside your coat pocket. If brain signals travel about as fast as seizures, it would take something like 1500 seconds (or 25 minutes) for some thought to travel from the middle of one brain half to the middle of another.
A 2020 paper was entitled "Kilohertz two-photon fluorescence microscopy imaging of neural activity in vivo." It used some fancy new technology to clock the speed of brain signals in a living mouse, a "latest and greatest" technology that takes thousands of snapshots every second. The paper has only one exact mention of a speed: supplementary Figure 5 of the paper refers to a calcium propagating speed of about 25 microns per second, which is a very slow speed of only about 0.0025 centimeters per second (about .02 millimeters per second). If human brain signals travel at anything like such a speed, the brain must be way, way too slow to be the cause of instant recall and fast problem solving.
We do not think at anything remotely like the speed of brains. We do not recall at anything remotely like the speed of brains. We think and recall at the speed of souls.