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Francis Crick and Christof Koch
Consciousness and Neuroscience
Cerebral Cortex 8: 97-107, 1998

The main purposes of this review are to set out for neuroscientists one possible approach to the problem of consciousness and to describe the relevant ongoing experimental work. We have not attempted an exhaustive review of other approaches.

We can state bluntly the major question that neuroscience must first answer: It is probable that at any moment some active neuronal processes in your head correlate with consciousness, while others do not; what is the difference between them? In particular, are the neurons involved of any particular neuronal type? What is special (if anything) about their connections? And what is special (if anything)about their way of firing? The neuronal correlate of consciousness if often referred to as the NCC. Whenever some information is represented in the NCC it is represented in consciousness.

from the introduction to the paper

"Consciousness and Neuroscience" was used in a discussion of consciousness as an area of ongoing research in the Senior Seminar in Neural and Behavioral Sciences during spring semester, 1999. The following are comments on the article by participants in that seminar.

Name: A. Forray
Username: aforray
Subject: Crick and Koch
Date: Fri Feb 26 17:15:39 EST 1999
Overall I did not like this article. While it did bring up some interesting points and questions like the binding problem and how is meaning generated in the brain, in the end the article created more questions than it answered. The article seemed to jump around from one idea to the other without fully explaining them. I found that much of the discussion on cortical area V1 was not very clear, and I had trouble following some of the examples presented.

The idea of a neuronal correlate of consciousness (NCC) seemed plausible, although I found that an attempt to depict which neurons are involved in NCC is to a certain point futile. Not only are there millions of neurons in the brain that could be involved, but due to brain plasticity the neurons used for a given aspect of consciousness may change at any given moment.

Crick and Koch's argument that the usefulness of visual consciousness is to produce the best interpretation of the visual scene based on past experience is valid. Although I see this development as a secondary quality of consciousness; it developed after humans became conscious. I don't agree with the authors when they use this idea in the statement: To be conscious, we have argued, there must be an explicit representation of each aspect of visual consciousness (p. 13). What about people that are born blind, are they unconscious because they cannot see? Or what about someone that is born blind and deaf, are they also unconscious? Or maybe I am just misinterpreting Crick and Koch.

There is no doubt that there is much to be learned about consciousness by studying the visual system. The visual system is a good place to begin in the attempt to identify neurons involved in consciousness, as can be seen by the experiment with recordings from single neurons in the superior temporal sulcus of a macaque monkey. While this a step forward in the correlation between brain and consciousness, neuroscientists have a ways to go.

Name: Noreen Khan
Subject: Consciousness and Neurscience
Date: Sun Feb 28 13:34:17 EST 1999
I appreciate Crick and Koch's insistence that consciousness is truly a scientific problem, best studied by neuroscientists. They are taking on the responsibility of answering this question instead of passing it on to philosophers, who further pass it back to neuroscientists. I also appreciate the fact that they present many potential experiments and approaches to answer the questions they posed. Unlike many of the authors in Searle's book who left us with more questions than possible solutions, Crick and Koch offer many directions in which the research can be taken. They seem to believe that the mystery of consciousness is one that may be solved only through aggressive scientific inquery.

Though, I appreciate their ambitious attempt to study conscoiusness, I don't know whether they will actually ever find a NCC (neuronal correlate of consciousnes). What they observe from different studies may not neccessarily be consciousness. For example, they talk about studies where they use bistable percepts and note which neurons are involved in the changing percepts. How can they be sure that the neurons involved are truly NCC and not differences in the processing of different input? Perhaps the difference in the percepts lies in the different input the monkey is receieving at the given moment, such as different depth perception. They address this problem briefly when they discuss the problem of "meaning", but they don't provide an answer to this problem. In addition, they claim that consciousness is a result of interaction between new input and past experiences. However they don't propose a way to examine this relationship. I understand that with our limited knowlege of these processes it may not be feasible to study these relationships right now, but will we ever have the capability of studying these questions?

The experiments they describe, though they may not be able answer the question of consciousness, will provide a better understanding of the brain. Perhaps future studies may eventually even solve the question of consciousness if they are able to better prove that NCC is truly what we call consciousness. Thus these attempts are certainly worthwhile.

Name: Kelly
Username: kmack
Subject: visual system & consciousness
Date: Sun Feb 28 18:58:25 EST 1999
Crick and Koch's article brings insight and frustration into our exploration of consciousness. The most helpful points are those that they put aside for further discussion or to take up later, such as the definition of consciousness and whether (and to what extent) animals other that humans have consciousness. This is good in that it focuses their argument although I personally believe that they are a little gruff in their dismissal, especially their pretty apparent disregard of the usefulness of philosophers and the arguments that they consider.

The authors seem to summarize research concerning visual processing fairly well although they lost me on some of the explanations such as the studies evolving gratings and directions. Going over these things in class again might be helpful. And I like the idea of focusing on one aspect of consciousness to find a way in.

Perhaps the frustrating aspect of this article is that so many ways of experimenting are brought up but I felt that Crick and Koch did very little in the way of making the connections to consciousness. They never really went as far as to explain why they think visual processing is an important and valid aspect of consciousness to study. My reasoning is that visual processing is an example of how we take in information, process it, relate it to previous knowledge, and use it consciously (such as while driving to avoid colliding with other cars). But possibly even more important is that we do know some of the brain anatomy and so there are some good starting places.

In essence, I find it useful that Crick and Koch review a great deal of experimentation but they stop there, without delving into what experiments were most helpful and should (or could) be continued to reveal more. In order to supplement the article and relate it more to the study of consciousness, it is important that we consistently refer the experimentation back to our idea of consciousness so that we can know where we stand and in which direction it may be most useful to move.

Name: jennifer McCallum
Subject: Crick and Koch
Date: Sun Feb 28 20:21:44 EST 1999

The Crick and Koch paper has left me feeling quite uninspired. I am not completely sure that this is due to their writing style, or the topic of consciousness in general. Regardless, I will write now more of what is my general reaction. Unfortunately my lack of enthusiasm will probably shine through in this essay.

First I would like to address why it is, I think, that I may be feeling so uninspired. The article begins with the stance that philosophy should be put aside for the time being in favor of doing real scientific investigations. I was disappointed to see that putting philosophy aside meant only a duration of 13 pages or so. In the middle of the paper Crick and Koch analogize understanding consciousness to understanding to "livingness" in terms of dead molecules. If I am correct, the idea is that something very different can arise from a substance(s) when that substance(s) interacts with other substances in complex ways. I really liked this analogy because it allows the nervous system and its molecules to account for consciousness in a way that does not require some special, far out explanation.

However, in the end of the paper there is a jump back to philosophy with an emphasis on the question of how the brain derives meaning. How did we get here from a search for the neural correlate of consciousness? It is my understanding that the brain has learning mechanisms. It is my guess that these learning mechanisms in combination with biological as well as cultural evolution are capable of establishing meaning. This is unquestionably an oversimplification, and perhaps even something which I am not myself feeling particularly ready to explain, but its better than the implication that meaning are innate in the brain.

I think Crick and Koch are on a good path to understanding consciousness by trying to find the NCC. I think they are swaying from this path however by trying to find meaning (I assume in the sense that John Searle would define it) from neurons in the brain. Such a question can be put on hold or left to the evolutionists. Consciousness itself, it might be safe to say, is an adaptation that has been selected for. It seems plausible that in an evolutionary sense, on-line systems (as described by Crick and Koch) preceded consciousness. This of course leads to the question of when consciousness came about and who has it. This is a difficult question to address, but I like the way Crick and Koch handle it. That is, they suggest for now, that we just try to understand human consciousness before determining who else has it. This may not be the proper place to start, but it beats debating whether fish and rocks are conscious. Someone has to make a stand and move forward. This is precisely, for better or worse, what Crick and Koch have accomplished.

Name: Sarah Zimov
Subject: Crick and Koch
Date: Mon Mar 1 08:23:26 EST 1999

I felt the article by Crick and Koch was good in that it split up the question of conciousness into an experimentally relavent question. At the very beginning they introduce the idea of a neural correlate of conciousness (NCC). Then they set aside a lot of the topics that usually detract from profitable study, (1) definition of conciousness, (2) language not necessary for conciousness, (3) other (lower) species conciousness, and (4) forms of conciousness (self-conciousness).

Then they introduce the visual system as an appropriate place to begin experimention relating to the NCC. They also introduced the binding problem and zombies. I agree with them that the visual system is a good place to start. First, we know a lot about it already. And second, it seems fairly easy to measure in non-human primates. At first I was wondering how they could possibly determine how a monkey percieves things (especially in the case of blindsight). But in reading further the experimental methods seemed clear and relatively straightforward for a test of perception.

They also made an interesting hypothesis. They state as a hypothesis that "the brain always tries to use the quickest appropriate pathway for the situation at hand." They state that the on-line (zombie) system would take this pathway and I'm assuming avoid the NCC. This is a nice hypothesis, but they give no evidence at all for it, nor do they suggest a way of testing it.

That's not to say that they don't have any support for their claims. They also introduce the V1 hypothesis:"Activity in V1 may be necessary for vivid and veridical visual consciousness...,but we suggest that the firing of none of the neurons in V1 directly correlates with what we conciously see." In this case, they give evides to support their claim.

At the end of their paper they briefly discuss philosophers and qualia, the problem of meaning and future experiments. Their discussion of philosophy is brief, but rambling. They start off discussing qualia, then move on to the analogy between "livingness and conciousness." Then they go back to qualia and break the hard problem into workable questions and end up answering two of them - private experiences and the function of conciousness. Then they briefly go into the problem of meaning....The section of future experiments was helpful in that they attempted to give direction to research on conciousness. I liked their last statement before the finale- that finding the NCC will not be enough, we'll need a complete theory of concioussness and ints functional role. They speculate that eventually biologists won't really worry about conciousness- they will"just want to know how it evolved, how it develops, and what it can do."

Name: Luise Pernar
Username: lpernar
Subject: Crick and Koch
Date: Mon Mar 1 10:33:48 EST 1999
Sorry this is late.

I believe Crick and Koch pin down well what the questions must be that neuroscience has to answer in terms of consciousness. However, I believe that the assumptions the two bring to the discussion are notvery well based in fact - or at least not in fact Crick and Koch reveal. They state several believes they bring to the investigation but fail to explain where theses assumptions come from. For instance, they state that higher mamals have consciousness despite a lack of language, showing that language is unnecessary for consciousness. THe problem I have with this is that I was under the impression that we did not know animals had consciousness. So how can Crick and Koch make this point and reject the significance of language along with this acceptance?

Also, the two reject the significance of studying self-consciousness. While I understand that they want to start with simple consciousness, such as visual consciousness, they seem to suggest that self-consciousness is not a valid construct to study.

I was glad to see that Crick and Koch speak of zombie possibilities - such as sports players who react before the visual input they reacted to could have reached them. This clarifies the point we discussed in one of the earlier sessions - is consciousness necessarily always involved in our wake behavior?

As Crick and Koch begin to discuss the data they have about conscousness, I began geting a little lost. First, the two made many assumptions, i.e. this memory is important for consciousness, this isn't etc. without following them up. Second, I wasnot entirely sure how most of the experiemnts the two cited showed much about consciouness. I think the article was quite interesting, but I am not sure I saw the significance of all the points made and evidence presented.

Name: Bindu Krishna
Username: hkrishna
Subject: Crick and Koch
Date: Mon Mar 1 12:31:39 EST 1999
I appreciated this paper on several levels. I liked how Crick and Koch related all the aspects of consciousness and discussed them. They addressed philosophy, psychology, as well as neurobiology. In particular, I was glad they mentioned qualia and zombies because those were topics which were constantly used by the philosophers. When I read Searle I thought that unconscious zombies were just a philosophical construct. However, Crick and Koch concede that zombies can exist to a certain degree. I also liked how Crick and Koch mentioned the working memory and aspects of attention. We study this in Human Cognition and it is pleasing to see that there is some connection between psychology and biology on the topic of consciousness. I also appreciated Crick and Koch for attempting to explaini consciousness in scientific terms. That is, they took this topic from the abstract and tried to pinpoint concrete elements. They further went on to support their idea of the visual consciousness. I can see how vision would be one of the first areas identified in consciousness. Much of our input comes from vision. However, I feel that this is also where Crick and Koch's problems begin. They have this hypothesis that they explain, but they never really provide proof for it. Perhaps it is because there haven't been enough experiments thus far. Yet they list these other experiments which are somewhat connected to their theory, and never explain any of them clearly. Crick and Koch do not elaborate on why these things prove what they do. For example, the bistable perception experiments were interesting, but I did not really get an idea of how much it was related to what they were studying. It seems to me that Crick and Koch were giving an overview of the current direction of consciousness in the world of neuroscience. However, instead of just an overview they also included their hypothesis without clearly conncecting the rest of their paper. So it ends up being not really a review and not really an experimental paper. Though there were these issues with Crick and Koch, I must admit that I did get a lot out of the paper. Mostly I am now aware of the type of research which can be done to test some ideas of consciousness on a biological level.
Name: Neha Navsaria
Subject: consciousness and neuroscience
Date: Mon Mar 1 12:59:35 EST 1999

I wasn't entirely impressed by the paper by Crick and Koch. I was very happy with the fact that they clearly stated many assumptions and presented the reasons why they chose to do omit certain views and definitions and keep others.

In the beginning of the paper Crick and Koch mention that scientists have put aside the study of consciousness because they have always assumed it to be a philosophical problem, which I agree with. However I do not understand why they say that it is premature to study right now. They then go on to introduce the idea of NCC (neuronal correlate of consciousness) which is very important because it establishes the relationship between the brain and consciousness and alludes to the idea that some set of neuronal firings lead to levels of consciousness. I had problems with the fact that Crick and Koch didn't define consciousness in the beginning of the paper. I know that a concrete definition could not be given, but it was very hard to see where the rest of the paper was going when I didn't understand their view of consciousness. Everyone who reads this paper must have different definitions of consciousness. I also didn't understand why they made it a point to mention in the beginning that it would not be profitable to ask whether certain parts of the nervous system are conscious. If they did not want to focus on parts of the nervous system, then why did they spend most of the paper talking very specifically on visual consciousness? Also, the fact that they ignored the idea of hypnotic states, lucid dreaming and sleep walking did not impress me, especially when the prime focus of this paper was on visual consciousness. Dreaming still creates visual imagery; although it is not real, at some times it feels very real and sleep walking could be an example of the "zombie" state that they bring up later.

I find the ideas of visual representation quite interesting. I am really wondering if someone who has certain neurons destroyed can only see parts of a face, I know that when babies are developing their visual system, they cannot see a fact, but it is more like a blurred face with an emphasis on certain parts. I feel that that is what someone would see if they have damaged neurons.

Overall, I thought that this article presented many new thoughts and ideas. I think that the experimental findings were very valuable, but Crick and Koch consistently did not explain the significance of the results. They just presented the results without stating how it could contribute to a definition of consciousness, so I felt like I was reading many results from experiments and that was it.

Name: Erin Brown
Subject: Crick and Koch
Date: Mon Mar 1 15:41:39 EST 1999
I felt that the article by Crick and Koch to be a very useful tool in beginning a scientific approach to understanding consciousness. While it is certainly only the beginning of work to be done, I felt that the authors stated their paradigm of thinking about the consciousness problems (the NCC idea) clearly without attempting to lead the reader to believe it to be any more plausible than it actually was. The authors were aware of how litle understanding they actually had in the area of consciousness, and did a very respectable job in working on the problem despite this. Their collections of experiments and ideas created an interesting start for further experimentation

I liked the idea of the NCC, in that it provided an interesting way of looking at issues we had difficulty quantifying in class. For instance, our discussion of acting without first thinking about our actions, as in sports and dangerous situations, was mirrored in their example of the tennis player and the track sprinter. The physiological basis they found in the V1 neurons, which they identified as not being part of the NCC illustrated one possible application of this paradigm.

The authors did not say that this was the only possible functioning of the neurons. They clearly stated that the functioning of NCC neurons were able to affect the output of the V1 neurons. This illustrates one way in which 'conscious' thought can influence 'unconscious' behavior, or in this case, input.

The point that they make about the possible shortest pathway theory is interesting. It helps me to think about the way that acting unconsciously may be more effective. It also explains how disruption of some functioning does not necessarily result in loss of function for the entire system,as in their illustration of the patient who reported not being able to see the dot, yet correctly identifying its movement. This is an interesting idea which needs a great deal more experimentation.

Overall, that statement summarizes my feelings on the entire article. It is an interesting scientific start which needs more experimentation. I do not think that the authors intended for thier work to be any more or less than that, and I think it is a commendable attempt.

Name: Christina George
Subject: Crick and Koch
Date: Fri Mar 12 22:07:46 EST 1999
The idea to view the visual aspect of consciousness for its richness in content and ease in avoiding ethical repercussions is valid. I thought that the entire article presented many fascinating ideas though I cannot say that these analyses helped in understanding consciousness better.

I thought the authors' mention of consciousness not being absolutely necessary for behavior to occur was interesting. The authors claim that a tennis player reacts to a fast serve before actually seeing the ball. In my human cognition class, I have read studies concerned with this same idea. Subjects are presented with a visual-spatial task and are also presented with charged vocabulary such as "rude", "mean", or "angry." These words, however, are not "consciously" seen by the subjects. After the experiment, a test to see whether or not behavior is affected by those charged words is given unbeknownst to the subjects. Results show that subjects do, in fact, behave more impatient and impolite, in comparison to the control subjects who were presented with no words whatsoever. Therefore, I feel that Crick and Koch, are wrong to say that the tennis player does not see the ball. Instead, I feel that he or she does see the ball--just not consciously. The consciousness of the ball comes later.

Throughout the article, I thought that the authors presented valid questions that need to be answered to further understand consciousness in terms of vision. One example is the question of what is essential for visual consciousness. However, when they go on to discuss the answer to this question, the authors focus on the ideas of working, short-term, episodic and iconic memories. These are not fully explained neurologically and therefore seem to stray from the idea of NCC (neuronal correlate of consciousness). Other experiments cited by the author, however, do mention brain regions and damage thereof. They make efforts to correlate the abilities of someone with damage to cortical area V1 and their disabilities thereby creating a correlation to the amount of consciousness tied to that region.

In my opinion, this is the most logical way to approach the vastly un-understood field of consciousness. The effort to build a model is noteworthy. The idea of the connectedness between the unconscious on-line system and the conscious seeing system tries to assign brain areas as components in the visual consciousness system. It is a decent model because it answers questions to situations where only certain things are able to be seen by someone while there seems to be responses to these unseen things. It is the work of pieces of the network not working in full harmony that cause these types of phenomenon.

Overall, I feel that Crick and Koch make good use of neuronal experiments to form some type of NCC. As they explicitly mention, these ideas serve to construct a framework for further research into consciousness. Their framework involves the intangible aspects of different types of memories and qualia and attempts to link these things to the tangible brain regions and neurons. Basically, they have recanted what many, if not all, scientists studying consciousness have said--Consciousness somehow involves neurons but the question of how delivers a hugely complex answer that is no where near its discovery.

Name: leland kass
Subject: Crick and Koch
Date: Sun Mar 14 20:49:00 EST 1999
After reading Crick and Koch¹s (1998) paper Consciousness and Neuroscience, I was both confused and intrigued. Throughout the entire, lengthy discussion, I kept wondering the relevance of their arguments to consciousness. I felt that they did an extremely poor job of explaining how the visual system and the following experiments related to the essence of consciousness. Perhaps I was (and still am) missing an important part. I do not understand how their article was some sort of proof of the existence of consciousness and what made it even more difficult is that they failed to ever define their version of consciousness. The idea of a neural correlate of consciousness (NCC) makes sense, although I personally do not believe that there is a standard NCC that can ever be charted. They argue that the problem of consciousness must be understood before a definition is reached, but how do they expect to figure out the problem if they do not have a general idea of what they are looking for? On top of that was their belief that humans should be studied prior to less complicated mammals. Their top down approach to looking at consciousness was interesting, but extremely ambitious and too overwhelming. I wonder if this is because they question the existence of consciousness in non-humans (despite the fact that they refer to macaques and other primates as possessing consciousness). I enjoyed reading about the visual experiments, but as I stated before, I feel that they were not necessarily proof of consciousness. The idea of testing binocular rivalry was interesting. The on-line versus seeing systems seem substantially supported, and the fact that the firing changes depending on the input to the eyes further supports it, but how does a difference in firing correspond to consciousness per se? Couldn¹t the firing be due to an extraneous factor or could it be part of the unconsciousness on-line system rather than the conscious seeing system? This was never discussed. The electrical stimulation discussion seemed even more ambiguous. They talked about how 50% of the cells recorded displayed a quantitative relationship between monkey performance and neuronal discharge.How do we know that that much is not chance? More importantly, what about the other 50% of the cells? The authors even say that it is possible that the monkeys are too well-trained and this is reflected in the close correspondance. The task was not explained so it is difficult to determine what the monkeys were performing and how it related to this ³consciousness² that is never really discussed. The most relevant part of the paper came at the end when it was brought up that consciousness cannot be explained by actions of parts of the brains. Because this is ultimately what I was thinking during the entire paper, I feel it needed to be addressed. However, if this is true, why are they attempting to explain consciousness with all these experiments that are looking at parts of the brain and not the whole? The idea of qualia seemed particularly negelcted until now and all along, the questions such as ³do you see the color blue as the same color blue that I see² are pertinent in the examination of consciousness. The idea of meaning and whether it can be expressed in neural terms is questionable. Say we do find a neural component to consciousness, does that mean that two people, simply because they have identical neural firings, are having the same experience? I feel that it is impossible to ever determine this answer and this is precisely why consciousness is not limited to neural circuitry.
Name: Maushumi Mavinkurve
Username: mmavinku
Subject: Consciousness and Neuroscience, by Crick and Koch
Date: Sun Mar 14 23:24:40 EST 1999

The paper written by Crick and Koch on Consciousness and Neuroscience has brought up some interesting points as well as confused me. Their opening remark that consiousness is a scientific problem is quite strong. Although I do feel that there are parts of consciousness that cannot be explained biologically, I felt that their ideas and topics were supported well through biological examples. The paper was more of an attempt to discuss how the visual system and consciousness are related, rather than neuroscience, which spans several areas and is too much to cover in a paper. What confused me about the paper was that it consisted of almost an overload of several examples and their collegues ideas which they would refer to but never explain well enough to get an understanding of the idea.

Amongst the interesting parts of this paper a few stand out, such as their description of why we have visual consciousness, which is in order to best explain currently the visual scene with respect to past experience and that this visual interpretation made is used to plan motor output of some sort. Their discussion of neuronal correlate of consciousness, NCC was another topic which I thought did make alot of sense. I believe that the idea that the NCC could be a global signal, one that every neuron or structure can possess, is most likely. As Crick and Koch said in the paper, this is a very complex idea and in my opinion one that we cannot even begin to study. Their description of the on-line system and the seeing system didn't was extremely confusing to me not only did I not understand each term but I did not understand the relationship between the two terms.

The last part of the article that I got alot out of was their discussion on the problem of Qualia. I thought that it was rather amusing as well as very true, Crick and Koch statement about "Neuroscientists know only a few basics of neuroscience," and that there is no thorough theory of the overal activities of the brain. They attempted to describe subjective experience as a possible difference in a high-level visual cortical area can still be associated with a difference in motor stage. This difference is what I believe they are saying to be the subjective difference of experiences between people.

Name: Anne Frederickson
Subject: Crick and Koch
Date: Mon Mar 15 09:25:15 EST 1999
In their article, Crick and Koch do a good job of outlining current lines of research that address the problem of consciousness, specifically, that which is related to vision. In addition, they present specific ideas for future research, which is often lacking from review articles such as this one. However, I had a problem with their definition of consciousness in general. Crick and Koch fail to present a clear idea of what consciousness is.

Crick and Koch claim that it is premature to have a formal definition of consciousness because it would be “misleading or overly restrictive.” However, they don’t even offer a tentative definition. Instead, they skirt the issue. They claim that higher mammals are conscious, but not lower animals. I fail to see how they can come to this conclusion without a definition. In addition, by failing to address the issue, they are simply continuing from where the philosophers left off. They can write all they want on the issue of consciousness, however, in the end, before we can make substantial gains in the area, we need to have an idea of what we are studying. Otherwise, we will never know if we have found what we are looking for. Presumably, much of neurological research is based on making changes to the nervous system and watching for external, behavioral changes. How can we possibly observe a change if we don’t know what is normal?

This leads into another issue that I have with Crick and Koch’s article. They claim to be looking for the NCC of consciousness. It seems that they are looking for a pattern of activation across the nervous system that is consciousness and without which there is no consciousness. It occurs to me that consciousness may be nothing more than a name for a bunch of behaviors that puzzle us. Perhaps it is not really consciousness that we should be studying but rather each of these behaviors. Consciousness may be too broad and ambiguous a category to adequately study. It may be more fruitful to study the NCC of pain, visual imagery, and self-awareness rather than looking for the broad category of consciousness.

We have still not defined consciousness to my satisfaction. Perhaps we, as humans, have not reaching the point where we have the knowledge to adequately do so. Perhaps it is an issue better left to the philosophers. However, as scientists, I think it is a bad idea to approach the issue at the level of consciousness. Despite the beginning of their article, I think Crick and Koch acknowledge this fact and do a good job of focusing on vision as their particular behavior associated with consciousness. It is only by making small stabs at behavior that we can even hope to make a dent in our understanding of consciousness.

Name: Jonathan Ball
Subject: Crick and Koch
Date: Mon Mar 15 11:17:53 EST 1999

On the whole I found this article really interesting. I think there is something to be said for laying aside problems that haven’t been answered despite 2000 or so years of trying to collect some actual data. It seems logical that with a better understanding of how the brain performs many of its task it might be possible to come up with a better philosophical theory of the mind. In addition this understanding may help unify many of the current and seemingly diverent theoritical models and elimante those that don’t work on a neurological level.

One of the ideas that was talked about in this paper was the notion of a conitinum of consciousness from lower order animals to humans. If one is going to accept that consciousness is a biological process then differences between organisms, at least higher verebrates, must be a degree and not of kind. I also applaud Crick and Koch statement that language can add to consciousness but it isn’t inherently neccessary. The idea of a continum of conciousness could lead to a interesting area of study that I think Crick and Koch failed to mention, that of comparative psycology. I know that this isn’t a new field, but I don’t think it has ever focused explicity on consciousness. Like the lab we talked about in class last week adding genes in sequence to find the cause of life, it might be valuable to study and compare the conciousness of species.

Crick and Koch also came up with what I felt was a strong argument by analogy about why it is useful to study the brain to understand consciousness; they argued that once it would have seemed illogical to believe that life could arise from “dead” molecules. The reason that I like this arguement so much is that I feel I gives a possible clue as to how complex human consciousness might be. If in fact neuronal behavior is to conciousness than molecules are to life than it may be possible to have an understanding of the process of consciousness without being able to directly understand or predict its results. What I mean is that neural behavior may relate in such a complex manner to consciousness, perhaps not just spacially but temporally, that it may be impossible to understand it from from the biological level of analysis even though biology is the source of consciounsess. This is similar to part of Dennett arguement about the Intentional, the Design and the Psyical stance. (As a random aside, maybe in is neccessary to start thinking about consciounsess in 4 dimensions; 3-D space + time)

I found much of the blindsight and bivariate precept experiments interesting. I was facinated by the fact that there some neurons which follow imput while others seem change with changes in preception. This seems to be a solid piece of evidence for the hypothesis that consciounsess has a biological correlate. The problem is that this area of research still leaves the questions of how syntaxic information is given semantic meaning by the human “mind”. Without being able to answer this question we are still left with a brain in a chinese room.

I don’t want to come off as to critical of Crick and Koch I think that this line of research is not only useful, but essential to finally understanding consciounsess a product of biology. And in their defense they don’t claim that they are going to be able to answer all the questions of consciouness at once, but rather they are laying a foundation from which to build. I think that is the greatest part of this article; their research may require much tedious work to map out all the functions of all the neuronal systems in the brain, but at least they are willing to stop talking, roll up their sleaves and get to work actually finding answers.

Name: lauren hellew
Subject: Crick & Kock
Date: Mon Mar 15 11:51:39 EST 1999
I found Crick and Koch’s article on Consciousness and Neuroscience both interesting and frustrating. In particular, I liked the scientific nature of their approach to the study of consciousness, however, I found that their paper left me with more questions than answers.

I like the idea that there is a neuronal correlate of consciousness (NCC). Although I appreciate the need for simplification, I was slightly concerned with some of the assumptions which were made in order for consciousness to be described as such. In particular, the fact that they neglect to discuss self-consciousness in favor of visual consciousness was somewhat troublesome since self-consciousness seems to be the most difficult aspect of consciousness to explain. The choice to assume that only some types of specific neurons express the NCC also seems like an oversimplification. Also, the fact that they didn’t even attempt to define consciousness or to provide a working definition for the purpose of the article, made their position more difficult to follow and to understand.

I did think that Crick and Koch did a good job of presenting the V1 and frontal lobe hypotheses. The evidence from blindsight patients and experiments with isoluminant colors, the horizontal grating aftereffect, and PET imaging all seem to support the idea that one is not directly conscious of the features represented by the neural activity in the primary visual cortex (V1). It also seems possible that the NCC projects directly into the frontal lobes. This could explain why one might have the ability to act on visual input without actually “seeing” the relevant input. However, as Crick and Koch admit, the evidence does not prove these hypotheses to be true, and it certainly does not help to define the actual nature or location of the NCC.

We have been talking in class about the need for a more scientific approach to the study of consciousness, and I think that the Crick and Koch’s paper addresses this issue very well. The problem seems to be the lack of knowledge and research in the area, not necessarily their analysis of the available information. It seems that such an approach has provided some important information about consciousness, however, it is obvious that much more research needs to be done in this area before we can come to any real conclusions about the nature of consciousness.

Name: Rachel Kaplan
Subject: Crick & Koch
Date: Mon Mar 15 14:28:59 EST 1999
Crick's and Koch's "Consciousness & Neuroscience" is an excellent adjunct to Searle's "The Mystery of Consciousness." Crick and Koch (C & K) provide some background information about why we are conscious and then go on to discuss their approach to studying the neuronal correlate of consciousness (NCC).

They present the interesting idea that consciousness arose in order to enhance efficiency. It makes sense what they say about a "single conscious interpretation" serving to increase response time. I would have also liked an explanation, however, of how the "on-line" or unconscious system connects with the "seeing" or conscious system to create this unitary perception.

I think it was wise of C & K to focus on the visual system given its powerful affect on our consciousness. Another smart choice might have been the olfactory system given that of all the senses, smell is supposedly the strongest inducer of memories. C & K outline some interesting information on the nature of visual representation. They propose that there are different groups of like neurons (which function in the "on-line" system) for each part of the visual representation of the face, which if destroyed would prevent a person from being able to recognize a face but might leave in tact his ability to identify aspects of a face.

The researchers present convincing evidence for the existence of the "off-line" system. They cite observations on patient D.F. done by Milner, Perrett et al. (1991), which are reminiscent of what Sachs saw with his patients: material which served as the basis for the movie "Awakenings."

The "seeing" system has been examined using the electrical brain stimulation approach. This seems to be a very useful, clean-cut approach; however, I do not understand what the authors mean when they say that "events caused by direct cortical stimulation were back-dated to the beginning of the stimulation period" (C & K).

C & K next mention the "VI hypothesis" which states that activity in the VI is entirely "on-line" due to the recoding of the "explicit aspects of the representation," which occurs in every stage in the visual ladder (C & K). I'm skeptical of this hypothesis because of the major assumptions they make and because of the fact that their supporting experiments seem to be all over the place. There just seem to be too many variables ever to prove this hypothesis definitively.

The frontal lobe hypothesis requires perhaps more testing than the VI hypothesis; however, the large-scale experiments with monkeys which they suggest, seem likely to provide more conclusive results.

The authors next address philosophical matters and qualia. I wholeheartedly agree with C & K when they mention that neuroscientists should be aware of the philosophers' questions on consciousness, but that they should not let the on-going debates interfere with their experiments. Notions of consciousness are ever changing and may only become more solid with the introduction of hard, scientific evidence. Let the scientists approach consciousness by every and any angle imaginable.

The scientists do a good job discussing issues surrounding qualia. They note that our subjective experience is influenced by our past experiences; that is why different cultures have been shown to "see" colors differently.

The designation of meaning is another hot topic which the researchers address. They point out that although a correlation may be found between a neuronal firing and a segment of a visual array, this does not prove that the firing is connected with the NCC. The main problem as C & K see it, though, is how is the meaning of particular firings, i.e. of a face, communicated throughout the brain? When it comes down to it, it seems that all we have are firings and more firings. When do the firings start to take on meaning? C & K present an unsatisfying general view on this matter.

The researchers end by discussing promising-sounding future experiments. I can't help being a bit wary, however, of any experiments done on this area given all the assumptions that need to be made and all the inconclusive results found from previous experiments. It is important for us skeptics in particular, however, to keep in mind that we are moving forward however slow the progress.

Name: Dan Weiser
Subject: C and K on C and N
Date: Mon Mar 15 15:15:36 EST 1999

I appreciated the non-confrontational approach that Crick and Koch took in their article on consciousness. Rather than dwelling on the debates that Searle discussed in his book, they went forward with what we know and where to go from there. They raised many questions for which there may be answers in the not-too-distant future. Crick and Koch propose that the neuronal correlate of consciousness (NCC) is necessarily global, though only particular neurons express the NCC. With this idea, we're essentially lead to believe that consciousness is a function of the brain just as vision, hearing, memory, etc. are. Though the difference is that we have narrowed down the most probable locations of visual representation, for example, but not the locations of conscious representation. Is it really possible to find areas of the brain that can be specifically correlated with consciousness? That is, the kind of conscious/unconscious behaviors we talk of in abstract, non-definitive kinds of ways? I am not certain that the authors did an adequate job of convincing me that consciousness can be described solely in terms of neuronal inputs, outputs and connections. Perhaps I am of the mindset that I don't want to believe that our consciousness can be reduced to something completely understandable by the human brain. While I don't see that as a possibility - we are much too complex for that, at least for now - the goal of this article was to propose such a way to figure out the mystery of consciousness. Crick and Koch do make strides in ways that we have not seen before by suggesting actual neuronal circuitry that they claim to be involved with the conscious (seeing) and unconscious (on-line) systems. Intriguing is that activity in V1, cells directly involved in visual processes, does not necessarily correlate with consciousness. It is difficult to imagine consciousness without senses, such as vision. And indeed, the authors say directly that to be conscious, "there must be an explicit representation of each aspect of visual consciousness." What Crick and Kock discuss in terms of the nature of subjective experiences - an issue philosophers have also been tackling - has always fascinated me. The blue sky may be "seen" differently in my mind that in someone else's. Though how is there a way to differentiate between the representations that each individual has? This is all consciousness, and the part of consciousness that we are far from understanding. Though the goal is finding the answers to explain consciousness, I am skeptical that there are any answers to be found.

Name: Melissa Bromwell
Subject: Crick and Koch
Date: Mon Mar 15 17:00:21 EST 1999
Crick and Koch's article expanded the neuroscientific understanding of consciousness to a degree far greater than Searle's book. I was particularly impressed by the way in which they began their article, noting that most scientists either consider consciousness to be a philosophical issue or think that now is not the time to study consciousness; Crick and Koch's beliefs, the direct opposite of the aforementioned ones, are, for the most part, quite valid and carry an amount of responsibility not yet seen in the other theorists we have discussed. I had mixed feelings concerning their lack of interest in arguing the same issues that were throughout Searle's book; they quickly set them aside to be dealt with at a later time so that they could attempt to focus on moving forward. I was especially pleased by their admittance that no one really knows how consciousness can be defined, yet it created several doubts in me as to whether or not I could believe their article. While I realize that my sensory perceptions are included in the realm of consciousness, when I think of "consciousness," I immediately think of the continual stream of thoughts and feelings that runs through me each day. I cannot recall other theorists discussing consciousness in quite the same terms in which I think of it and therefore I cannot be certain that when I read an article about consciousness that I am learning anything about what I consider to be consciousness. For, example, while Crick and Koch were discussing the nature of the visual representation, they mentioned that "while the information needed to represent a face is contained in the firing of the ganglion cells…there is…no explicit representation of the face there," and later report that the visual representation is likely to be found in the cortex and some subcortical structures; without defining what they mean by "visual representation," it is difficult to accept that my picturing a face that is not within my immediate surroundings is only represented by a series of neuronal firings in my cortex when my imagining of the face seems too detailed and "photographic" to not be a part of my eyes. I have mentioned this to explain why I believe it is necessary to define consciousness and all of its components before setting out to decide where it originates. On the other hand, I recognize the importance of leaving some mysteries unsolved for the time being in order to attempt to advance the current body of knowledge concerning consciousness. Despite the ambiguities in the article, it provided a substantial amount of information to support Crick and Koch's theories and perhaps a more structured path for future studies to follow in exploring consciousness.
Name: Zach Hettinger
Subject: Crick and Koch
Date: Mon Mar 15 23:23:36 EST 1999
I thought that this paper presented a lot of interesting and thought provoking ideas, but I also found its lack of depth disappointing. One would think that with a title like Consciousness and Neuroscience a lot more would be explained by the end of the paper, instead they ask more questions than they answer and give often cursory examples that lack explanation.

One of the more interesting "guidelines" that they provide for future study of the nervous system is to focus in on humans and to avoid studying simpler animals until consciousness is better understood. This makes sense because you need to have a grasp or some kind of definition (which they also wish to avoid) of consciousness in humans, which we know exists, in order to study the existence of consciousness in other animals. Yet they do take the liberty of citing a lot of studies using primates. The unspoken assumption here is that primates are conscious, close enough in relation to humans, and allow for experiments that could not be performed on human subjects. Part of what makes this so interesting is that many other disciplines seek out the most simple of structures and try to build from lessons learned on those in order to reach their goal. The fact that scientists think that one must first understand all of consciousness in humans, who contain one of the most, if not the most complex form of consciousness, attests to the complexity of the problem in studying consciousness.

Crick and Koch also point out the importance of memory in consciousness. Without memory one can only react from instant to instant to stimuli. Memory allows a conscious organism to use past experiences to evaluate present situations. They do not say that memory equals consciousness, but that memory is an integral part of being consciousness, and without it consciousness could not exist.

All in all the paper brings up interesting points but lacks real substance.

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