Ms#: AM98029R
Title: Can The neuron in the brain implement symbolic systems?


The revised version of the manuscript #AM98029 titled "Can the neurons in the brain implement symbolic system?" is a considerable improvement over the previous version. Indeed, many of the grammatical and typographical errors have been corrected. On the other hand, the main argument of this manuscript remains weak. In general I must say that I would expect the author to write his paper himself instead of submitting half-baked ideas in bad English in the expectation that somebody else will do his job for him.

a) major

1) The main argument of this manuscript remains weak. To give an example, consider the claim "in the next four sections I will show that our knowledge at the neurobiological level is in conflict with the symbol hypothesis" which the author utters in page 7 of his manuscript. This claims is patently false. There is no neurobiological piece of evidence in the manuscript to refute the symbol hypothesis. Instead this manuscript convincingly make the point that whatever neurobiological evidence is presently (including the pieces of it described in the manuscript) does not support the symbol hypothesis. Refuting a hypothesis and failing to support it is not the same thing. It would certainly be easy to delete this and similar unsupported claims from the manuscript (this MUST be done). But the problem is worse and is an implicit one. Suppose that I make the following claim: "The neurons in the brain are not stochastic, in the sense that they are completely specified so that pyramidal neuron #123456788 in V1 of the brain of human being A is everywhere identical to pyramidal neuron #123456788 in V1 of the brain of human being B; further they are not stochastic in the sense that they are completely specified so pyramidal neuron #123456789 in V2 of the brain of human being A differs from pyramidal neuron #123456789 in V2 of the brain of human being B in specific ways ABCDEF for reasons related to well known difference between these two human beings". There is actually no evidence against this claim. Now, if I were to publish a paper that uses this argument the onus would be on me to either: 1) Provide proof supportive of the claim, or 2) Assume its truth (and thus it would be a very different sort of proposition, namely an assumption) and proceed logically from it. Since the author of #AM98029 can not prove that neurons are stochastic (if he has the relevance evidence now is the time to produce it) he should state exactly his assumption (i.e., that the neurons in the brain are stochastic) and call it an assumption. He is certainly free to also state that to his knowledge there is no evidence to negate the truth content of his cherished assumption.

2) The last sentence of the previous paragraph could replace most of section 4 of #AM98029. This section must be reduced by a lot as it does not strengthen the author's assumptions. For example, the "evidence" alluded to in Paragraph 3 of Page 9 is no evidence at all. Nobody has tried to compare stellate neuron #123456789 in area 17 of the brain of cat A to that of stellate neuron #123456789 in area 17 of Proof does not pop out of experiments for free. It only arises in experiments designed to test hypotheses (albeit not necessarily the one the experiments was designed for). However, I must admit that assumptions can be rendered less counterintuitive if there is no evidence to refute them so a check of the literature is seldom a waste of time. A couple of paragraphs of evidence of this sort (say paragraph 3 and 4 of P 11) together with a coherent presentation of the argument (say the bottom paragraph of P 9, and the paragraphs of P 10) would suffice for a new Section 4.

3) It is no accident that two referees thought the author's argument applied to the brain and the spinal cord. It never crossed Eccles mind that whatever he found in the spinal cord would not apply to the rest of the CNS. The same is true of almost everybody working in the spinal cord. The author is certainly free to limit his argument to whatever part of the nervous system he wishes to consider. But he should be upfront about it. The easiest way to go about it is to modify paragraph 3 of Page 7, as follows: ...the term "brain" in the strict sense to mean the vertebrate telencephalon and brain stem".

4) P 14,15 (Section 6): I still have trouble with the argument regarding coherent connectivity. The author should write his text in such a way that I (and other potential readers) can understand exactly what it is that he has in mind. It could help if he provided definitions. Also, it could if he provided an example. To this end he could substitute the word "element" by layer, column or area, etc., and explain himself concretely. Then if he wished to be general he could again convert to "element". To get back to the argument though, does the author imply that because of their spatial proximity the X neurons of layer 4 of a column in the superior colliculus and the I neurons of layer 4 in the same column of the superior colliculus must receive the same input from the frontal eye fields or the pars reticulata of the substantia nigra? If this is what he means he has his facts wrong. If this is the case I must insist that he has failed to prove that symbol tokens can not be handled by larger scale structures in the brain.

b) minor

1. Title: I suggest "Can Brain Neurons Implement Symbolic Systems?"

1. Abstract, lin2 (1) 2: This notion is based on the often implicit assumption that there is a symbolic system in the brain itself.

2 Page (P) 4, paragraph (p) 1, 1 2-4: the phrase "...framework, which they say is agreed as the appropriate way to study..." remains awkward. It is the English that is awkward not the argument. It is the author's responsibility (and not the referee's) to express the author's ideas in good prose. In any case, something like "...framework which is generally thought to reflect human..." would probably do.

3 P 4, p 1, 1 10: In English, no sentence is allowed 1) to start with a parenthesis and 2) with a parenthesis followed by a small letter. The author should modify the statement " ... world. they do mention connectionism later)" in a way that respects grammar good style.

4 P 4, p 4, 15 & 7: The author does not provide a list of the characteristics that he thinks are characteristic of neurons. Thus the pronoun "these" in the sentence "neuron with these characteristics" is meaningless in the strict grammatical sense pertaining to the job of pronouns in English syntax.

I suggest that he uses "realistic neurons" as follows: ...implementable by realistic neurons. In this article I will show that symbolic systems are in principle unimplementable with realistic neurons, and hence.... If he wishes he can define "realistic" to mean "neurons endowed with the properties of the real neurons that populate real brains" either before or after the first appearance of realistic in the text.

5. My objection regarding "consistent" is that the author means "self-consistent" .
6. My objections "how do you know", "this is not good enough", "how do you know that it is the right neurons that are being compared" , etc., can be dealt with as suggested in Major #1, above (and can not be dealt with as implied in the author's responses to my comments).

7. P 10, p 5, 13, fiber (instead if fibre).

8. P 14, p 5, 14: ...distributed. On the other hand, the use of higher levels of organization to implement symbol tokens would need to be based on primitive elements of...

9. P 18, p 5, 11: Does the author mean the following? "We don't know enough about neurons to build symbolic models with them"

10. P 22, p 4, 12: It shows that the notion that the brain implements symbolic systems is not well supported by what we currently know about it.