Related texts

[ Last updated 10 Sep 2003 ]

Bits about neuroscientists

Examples of misleading comments by neuroscientists that I found on the net. There are many more than what I got here, but I don't actually maintain this page properly, so what actually gets here is quite random.

If you want to check the validity of the statements that I make in this document, check in any neuroscience textbook. If you find any statement that I make here that is wrong, let me know.

The criterions for including a page here are:

The review in Nature Review Neuroscience of the "stereotyped connectivity" paper is actually the best example for such mis-information (and the commentary on Columbia site an extreme example). [12 Oct 2001] The Miller et al review is also a good example

1. "Definite plan"

Here is a review by four leading neuroscientists of the state of neuroscience in 2000 (Neural Science: A Century of Progress and the Mysteries that Remain, Albright, Jessell, Kandel, and Posner, Cell, Vol. 100, Neuron Vol. 25, S1-S55, February, 2000). These people definitely know that the connectivity in the cortex varies randomly across individuals([22 Sep 2003] I am not sure about Kandel anymore), but it does not stop from writing on p S12:
Even though the anatomical connections between neurons develop according to a definite plan, the strength and effectiveness are not entirely predetermined and can be altered by experience (Squire and Kandel, 1999).

The way the discussion is presented, that is intended to apply to all neural systems, including inside the cortex, where it is simply false.

It can be argued that the cortex is an exception and that the authors do not intend to include it, but that is not the way the review is written. The cortex is the most prominent neural tissue in this review (as in general in neuroscientific literature), so general statements are clearly intended to be applicable to the cortex too. There is no way a reader that does not already know the facts can figure out that this statement is false about the connectivity inside the cortex.

The closest the authors get to saying that the cortex is different in this respect is in the discussion of the development of the connections, where they say on p. S23:

In contrast, the more sophisticated cortical circuits associated with the processing of cognitive information, which emerge later in evolution and development, may require functional validation for the establishment of final patterns of connectivity (Shatz, 1997).
But there is no way to deduce from this that the connectivity inside the cortex is not according to a "definite plane".

The case for the "definite plan" is made on pages S20-S21. First, the authors mention the "resonance theory" from 1941 (I haven't read this one), which (they say) claims that making connections is largely random. Then they bring counter-evidence. The main evidence is Sperry's research in the retino-tectal connections in lower vertebrates. Then they mention motor axon projections in vertebrate embryos and axonal pathfinding in insect embryos. While this research is quite interesting, obviously it cannot tell us much on connections formation in the cortex (or anywhere in the mammalian brain, for that matter).

The authors quite carefully avoid mentioning the mammalian brain at that point of the discussion. They don't actually say that the results of the mentioned experiments can be projected to the cortex, but since their discussion is supposed to be general, the implication that it does is quite strong. They certainly don't give the reader any reason to suspect the applicability of the "definite plan" to the cortex.

Thus readers of this review will read the "definite plan" claim, and take it as applicable generally to all neural tissue, including the cortex (because it is mentioned many times in this article). Unless they already know about the variability across individuals in connectivity in the cortex, they cannot figure it out from this review. This is specially bad because this is an authoritative review by four leading neuroscientists in a highly respected journal, and people can reasonably expect to be able to rely on what it says. In the case of connectivity, they cannot.

2. Carla Shatz about connectivity in the brain

[2.1] On 17Apr97, Carla Shatz took part in a white-house conference on childhood development and learning[23Feb99: this page disappeared]. A more organized version of her remarks is here[14 Oct 2001: this page dead now], and I will use the latter. This talk is a good example of a neuroscientist confusing the rest of the public about the precision of connectivity in the brain, even though they know better.

[2.2] The main point of Dr. Shatz talk is that experience after birth is important in the wiring of the brain, and I have no problem with this point. The problem is what Dr Shatz says about the precision of connections.

[2.3] In the second paragraph of the 'The problem' section, Dr Shatz says: "So, the brain contains well over 1000 trillions connections and none of them are random!" In the following paragraph, she expands a little. Discussing visual and auditorial input, she says: "And then, once the growing axons reach their targets, they must select, from the millions possible neurons, just the right few with which to form synapses."

[2.4] First we should note that Dr. Shatz don't actually tells us what 'not random' or 'right few' mean. The natural interpretation, which non-neuroscientists will use, is that there is some plan for the connections, and each neuron select the right target neurons in accordance with this plan. Thus, for a non-neuroscientist, what Dr. Shatz says means that there is a plan that specifies exactly all the connections in the brain ("none of them are random").

[2.5] That is simply false. The main structure for thinking in the human brain is the cerebral cortex, and in it specific connections are almost totally stochastic. There are tendencies in coarse resolution (1mm), but at the level of individual connections each cortex is completely different from each other cortex (That is true for all mammals). In the cortex, neurons don't select the 'right few' neurons to synapse with: they synapse stochastically with some neurons that happen to be around the point their processes 'decide' to start to make connections.

[2.6] Dr. Shatz knows this better than I do, as she has been researching the connectivity of the brain for years, and never found individual connections in the cortex of any mammalian brain which are the same between individuals. Nor did any other the other researchers in the field.

[2.7] What about the examples that Dr. Shatz quotes, with the neurons that select the 'right few'? These examples are wrong on two accounts:

They are not accurate.
Neurons which selects exactly which neurons to contact (i.e. they have the same connections in all healthy individuals of the same species) haven't been seen anywhere in any mammalian brain. The most accurate connectivity is in cases when small populations of neurons are directed to other small populations (e.g. neurons from a specific whisker to a specific barrel in the rat), but even in this case the connections of each neuron are not completely specified (*).
Even that level of specificity is seen only outside the cerebral cortex.
The examples that Dr. Shatz brings are pathway leading to the cortex. These are important too, but when Dr. Shatz discusses the '1000 trillions connections' she clearly means the cortex. Outside the cortex, the only structure that contains that many connection is the cerebellum, which has a major role only in the learning and performing of accurate movements. The number of connections in the rest of the brain is far smaller than that.

[2.8] In 'The solution - not like a computer' Dr. Shatz describes how she thinks the precise connections are made: "The brain actually lays down a basic framework of circuits - the trunk lines - according to strict diagrams set by genetic blueprint. Then, way before the adult precise circuits are formed, the "switch" is turned on: Brain function itself completes the wiring process by running test patterns on the circuits and selecting correct connections and eliminating errors."

[2.9] The first sentence of this quote is a half-truth: while the brain does have a design, this design is in coarse structures. The exact connectivity of neurons is not defined at any stage of the development of the mammalian brain. If we remove the word 'strict' from this sentence, it is much closer to the truth.

[2.10] The second sentence is blatant nonsense: How can any part of the brain 'run test patterns' and 'select correct patterns' before it itself is connected properly? Dr. Shatz implicitly uses the analogy of electrical engineer running tests on an electrical circuit, but in the brain we don't have an engineer, and we don't have any mechanism that can 'select correct connections', because this mechanism itself would have to based on 'the correct connections' (**).

[2.11] The second sentence also enforces the notion of a plan: It does not make sense to talk about 'selecting correct connections' and 'eliminating errors', unless there is some plan so 'correct connections' are connections according to the plan, and errors are not. Thus Dr. Shatz does not leave any doubt in the non-neuroscientist reader/listener that she thinks there is a plan for the connections in the brain, which specifies all the connections.

[2.12] Why does Dr. Shatz tell her listeners/readers that there is a plan for the connections in the human brain, when there clearly isn't? First we should note that she does not actually say it: It is just strongly implied by the text. Hence one possibility that Dr. Shatz does not intend to imply that there is a plan for the connections.

[2.13] That is quite difficult to reconcile with the terms she uses ("select .. the right few", "select correct connections", "eliminate errors"), but maybe in the neuroscientists's jargon these have different meaning. In this case, that text (and other neuroscience texts) is very misleading for other people, which read it using the normal definitions of these terms, and hence take it as implicitly saying that there is a plan.

[2.14] The other possibility is that Dr. Shatz does believe that there is a precise plan for the connections in the brain, including the cortex. As I wrote above, this is simply false, because different brains have different connectivity, and Dr. Shatz knows that. In this case this is an example of a person believing two contradicting facts in the same time.

[2.15] In either case, an underlying reason for the mistake that Dr. Shatz (and other neuroscientists) does is the pressure from outside the field of neuroscience. This comes both from cognitive scientists, which advance theories that are incompatible with stochastic connectivity, and from the rest of the public, which prefers more 'positive' statements. Thus a statement like "the brain contains well over 1000 trillions connections and most of these are stochastic", even though much more accurate than the statement Dr. Shatz makes, would be received much less favorably both by the cognitive scientists and the rest of the public.

Dr. Shatz response (If I get any)

Somebody comments about it, and my response.

3. Bob Wyman on connectivity in the human brain

[18Oct98 the ridiculous statements have been eliminated from Bob Wyman's page. I don't know whether this happened in response to my e-mail message to him or this page or is unrelated, but it happened less than a month after the e-mail. ]

[3.1] In the first paragraph of his home page, Bob Wyman Says: "We have 10**11 - 10**12 neurons and each one has ~10**3 connections. Thus the brain has at least 10**14 connections. We know that each connection, as it develops in the embryo, is very specific."

[3.2] That is simply a blatant lie. We know that the bulk of these connections (in the cortex) are not specific, and vary stochastically between individuals, simply by the fact that we don't find any connections which are the same between individuals.

[3.3] Maybe Dr. Wyman does not know that, but his answer to my e-mail about this suggests otherwise. I asked if he really believes that sentence, and his answer was something like (unfortunately, I lost the actual message): " Yes. For example I can tell you approximately where a neuron from the retina synapse." like Dr. Shatz above he uses an example outside the cerebral cortex (and even outside the brain), and the example is actually not accurate (You cannot tell exactly which neurons the neuron from the retina is going to synapse).

Dr. Wyman response (If I get any)

4. 'Mind and Machine' module in the physics(!) department at Syracuse University

[4.1] The department of physics at Syracuse University apparently offers a module on mind and machines (in its 'Science for the 21st century'). In it there is a page about organization of the brain.

[4.2] The statement made in this page about the formation of connections is less blunt than in the two pages above: "While the overall program for determining which neurons should be connected together is under genetic control, it is external stimuli which are crucially important in determining what network connections are made."

[4.3] This statement is not even self-consistent, because the second part implies that genetic control is not 'crucially important in determining what network connections are made.' The contradiction with the first part is somewhat masked by using different terms (and even different tense) for the same concept ('which neurons should be connected' vs. 'what network connections are made.")

[4.4] The second part of the sentence is clearly correct, but the first part may or may not be correct, depending on the interpretation of the term 'overall program'. If this is interpreted as 'the coarse resolution program' then the sentence is correct. However, most of readers probably interpret the first part as saying the bulk of connections are determine by genetic control, which is clearly wrong (because they are different between individuals).

[4.5] A much worse statement comes two paragraphs later: "The fact that our neurons can rewire themselves "on the fly" has the consequence that our brain are amazingly robust - if a given neuron dies (which will have happened to something like 20 percent of our original neurons by the time we die!), our brain automatically undergoes a rewiring process in which new connections are made to circumvent the defunct neuron." This is a blatant lie. There isn't anything in the brain that can automatically compensate for a death of a neuron, and there isn't anything that even resembles an evidence for it.

To my surprise, I found almost exactly the same piece of rubbish on another page, this time in an answer service about science in Washington State University. In an answer to the question why a person can't grow new brain cells, which is overall reasonable, DrUniverse says: "But this [losing 10% of the cells] doesn't mean that you're only 90 percent as smart as when you were born. That's because even though you've lost some neurons, the ones that are left can form new branches of fibers and new connections, or synapses, between them." Again, this is false because we don't grow the fibers (dendrites and axons), but at least here they don't claim that there is an automatic compensation for each neuron.

Dr. Catterall response (If I get any)

DrUniverse response (If I get any)

5. Neural synchrony for 'binding'

In 9Jul98, Nature published a paper by Usher and Donnelly(also here) about visual synchrony. The authors state the hypothesis they are trying to support in the abstract: "An attractive scheme for binding visual features into a coherent percept consists of synchronizing the activity of their neural representation (Milner, 1974, Von Der Malsburg, 1981, Crick & Koch, 1990). If synchrony plays a major role in binding, one should expect that grouping and segmentation are facilitated in visual display that induce stimulus dependent synchrony by temporal manipulation"

The last sentence is plain nonsense, because all the theories that are postulated by the references given in the first sentence assume that all kinds of stimuli, not only result of temporal manipulations, induce stimulus dependent synchrony, which is used for binding. The example that is typically used is the binding of colour and shape of the same object. In addition, the temporal synchrony in these theories is inside the brain, while Usher & Donnelly are discussing temporal synchrony in the stimuli, i.e. outside the brain. Thus the data that Usher and Donnelly present tells us nothing about the theories that they are trying to support.

The experimental facts that Usher and Donnelly show, i.e. that human are sensitive to synchrony in the stimulus, is obviously a result of the fact that synchrony is a typical attribute of moving objects in the world, so humans use it (whether this is learned or in the genes is irrelevant here). Hence 'finding' this sensitivity tells us nothing about anything that happens inside the brain.

[11Mar2002] Here is a later review that does the same logical error.

Usher's response to a mail query I sent him.

6. Joseph LeDoux on the amygdala

I In the Overview LeDoux says:

Only by taking these systems apart in the brain have neuroscientists been able to figure out that these are different kinds of memory, rather than one memory with multiple forms of expression.

There isn't anything that can be even remotely considered as evidence for this assertion. On the other hand, severe damage to the amygdala has only relatively small affect on memories associated with emotions, while having huge effect on emotional responses. So it seems more likely that the amygdala has a role in emotional processes, rather than in memories.

Later in the same page, we find this:

Learning and responding to stimuli that warn of danger involves neural pathways that send information about the outside world to the amygdala, which determines the significance of the stimulus and triggers emotional responses, like freezing or fleeing, as well changes in the inner workings of the body's organs and glands.

The amygdala clearly does not trigger freezing or fleeing. These are done by other parts of the brain. There is no evidence that it "determines the significance of the stimulus", as opposed to being part of the system that does it, and it seems unlikely that such a small structure can do such complex determination. What LeDoux is doing is doing is to use evidence that the amygdala takes some part in some process as evidence that the amygdala performs the whole process. The rest of the discussion is based on this error.

7. Ramachandran on 'Mirror neurons'

[22Aug2002 The original page in feedmag is dead, but there is a much longer essay here. The important bits of the quote below appears almost verbatim on the second page (last big paragraph). In this Ramachandran makes it clear that he does think that the concept of "mirror neurons" is real. ]

Ramachandran starts his discussion of the Ventral Premotor Area this way :

My favorite region of the brain changes from year to year, but I'm currently fascinated by the rostral part of the ventral premotor area. Giacomo Rizzolatti at the University of Parma has elegantly explored the properties of neurons in this part of the brain -- the so-called "mirror" neurons, or "monkey see, monkey do" neurons. His research indicates that any given cell in this region will fire when a test monkey performs a single, highly specific action with its hand: pulling, pushing, tugging, picking up, grasping, etc. In addition, it appears that different neurons fire in response to different actions.
One might be tempted to think that these are motor "command" neurons, making muscles do certain things; however, the astonishing truth is that any given mirror neuron will also fire when the monkey in question observes another monkey (or even the experimenter) performing the same action! With knowledge of these neurons, you have the basis for understanding a host of very enigmatic aspects of the human mind: imitation learning, intentionality, "mind reading," empathy -- even the evolution of language. Anytime you watch someone else doing something (or even starting to do something), the corresponding mirror neuron might fire in your brain, thereby allowing you to "read" and understand another's intentions, and thus to develop a sophisticated "theory of other minds."

(My bolding)

The bold statement in the first paragraph is somewhat ambiguous, because it does not explicitly says that the 'given cell' is going to fire only when the monkey performs a 'single, highly specific action'. However, this (false) interpretation is natural for anybody that doesn't actually know all the facts, and hence would be very misleading to non-experts.

The bolded sentence in the second paragraph is much worse. The term 'given mirror neuron' can only be reasonably interpreted as 'a neuron that has been identified as a mirror neuron not on the basis of its firing pattern'. That is because if the mirror neuron was identified by its activity pattern then this sentence is a trivial tautology. Thus this sentence strongly implies that 'Mirror Neurons' can be identified by other means, which is simply false. The only way a 'mirror neuron' can be identified is by checking the activity patterns of many neurons until you find some that behave according to the definition of 'mirror neuron'.

An interesting question is what does Ramachandran himself thinks. Since he is an active neuroscientist, it is hard to believe that he doesn't know how 'mirror neurons' are identified. On the other hand, I don't think he is intentionally misleading the reader. My guess is that he believes that we will find ways to identifying 'mirror neurons' except by their activity pattern, and just failed to notice the border between experimental observations and his own beliefs.

My guess is based on the rest of the paragraph and the whole page, which shows that Ramachandran believes that 'Mirror Neurons' are fundamental feature of the brain. In fact, he goes as far as saying:

With such exciting developments, I predict that mirror neurons will do for psychology what DNA did for biology: they will provide a unifying framework and possibly even explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments.

To call this statement 'idiotic' would be a compliment.

8. 'Rewiring' in the brain

Here is a blurb an article in nature, in the home page of the principle author. The most standing out point in this text that it repetedly claims that the brain rewires itself. The study didn't show anything like rewiring. It showed changes in activity of neurons, presumably a result of changes in strenghths of synapses. It may be claimed that this is what 'rewiring' is supposed to mean, but that is not the way the word is normally understaood. The target audience of this blurb will interpret as meaning forming new "wires" (which in the brain presumably mean axons and denrites), and therefore will be mislead by it.

Interestingly, other commentaries on this article did not take up the 'rewiring' theme.

This page also contains a stunning example of the results of the"intelligent-neuron" misconception. It says:

In addition to figuring out how quickly brains can rewire themselves and accommodate new categories, he wants to find out whether the same neurons represent the same categories in different brains.
Obviously, the stochastic connectivity in the cortex rules this out, bu Earl Miller hasn't worked it out. Since he obviously knows that the connectivity varies randomly between individuals, it must be because he didn't yet consider the implications.

9. Nerve systems "like computers"

Here is the homepage of a researchers of C. Elegans (a 1mm long nematode with a fixed cellular structure). It says:
Nervous systems, like computers, rely on their components to be precisely connected.
That, ofcourse, is plain false for nervous systems in general. It is true for the nematode, and apparently this guy don't realize that more complex systems are not necessarily the same.

A response from Bill Walthal.

10. "interconnected in a precise and intricate manner"

[ 1 Apr 2003]

Here it says [ 20 Apr 2010 page gone by now]:

A neocortical column contains several thousand neurons interconnected in a precise and intricate manner.
The "precise" part is a straightforward lie. The list of the publications of this laboratory is here, so you can try to see if any of their publications justifies this statement.

Henry Markram's response to my e-mail about this .

================================================================= =================================================================

(*) As far as I know, this is true not only in mammalians, but in all vertebrates, and for most invertebrates that have a brain worth talking about.

(**) Note that I am not saying that there are no activity-dependent changes, or that these are not essential for normal development. It is just that these cannot be described as 'running test patterns' and 'selecting correct connections'.


Yehouda Harpaz