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Rating: 
Summary: Good
Review: For the last couple of years, few sicentific progress seems to have been made in the study of consicousness. Philosophical books do not claim to make much progress. I mean, philosophers have been debating over things like representationalism for over 20 years now. But science is supposed to be different. But as hard as I look, most recent books are nothing but reviews of the literature of the last decade and popular sicence, simplified for the lay reader, that seems to make no progress.
This book is not that different. Koch is one of the pioneers in the field, along with the late Francis Crick. It seems the quarrell between the nobelists Crick and Edelman is over, as can be seen in chapter 19 of this book, since mostly their theories agree on the important points. THAT is progress enough.
The bulk of the book is not about the neural correlates of consicousness at all, but about visual neuroscience, and the relationship between cosnciousness and memory and attention. All these chapters offer few truly novel insights, but are not to be skipped by the begginer. The ideas of neural assemblies and competition of neuronal coalitions have been around a while (Susan Greenfields work, and Taylor's Race for Consicousness), but it certainly is exiting to see the breaktrhoughs made with studies on binocular rivalry. Now it is hard to see how useful the unconscious homunculus can be as a theorethical tool. I read it on a joint paper Koch wrote with Crick in a collection edited by Metzinger, I did not get it then and I do not get it now. As I understand it, Koch just talks about a central executive in the frontal cortex, an idea not new nor very groundbreaking. Koch's idea on the necessity for involvent of frontal cortex (through intersignaling with posterior areas) in the NCC is confusing. Maybe differetn types of consciousness could clarify the concept. Sensory consciousness seems to only depend on posterior regions, while working-memory-type consicousness seems to need the frontal areas. It seems clear, considering Koch's ideas on qualia, that he means something like this.
There are some very important contributions, however. Chapter 6 almost resolves the debate on wether V1 is consicous (it is not), and as Koch points out, this is a positive thing, sicne it shows that cortical areas can be analyzed separatedly, and explaining their contribution to consicousness is possible. It would be magnificent if we could further reduce the candidate cortical areas further, if only slowly. I am skeptic of Koch's ideas that maybe different types of neurons can be so characterized. What if we found allegedly "conscious" neurons in V1? It seems to me more plausible that the role a neuron plays in context to the region it is in is far more important than ther cell type instead. Of course, Im speculating here.
But speculation is something Koch does quite well. However, as it is custom, scientists speculate on philosophical issues in their science books, and I like to wonder what philosophers would have to say about that. Lets see. Koch mantains that the function of consciousness is to summarize the present state of the world to the organism, so that it can plan accordingly. This is a very good function, but by no means a novel hypothesis. Cambell, i his book reference and consicousness, mantains that consicousness determines the reference of a demonstrative and therefore justifies the cognitive processing (planning) of the object refered too. Cambell is a philospher and argues for this point forcibly. So here Koch could be on the right track. What about qualia?
Qualia, Koch argues, are symbols, mental shorthand, for the vast content of those mental states. Qualia, then, are the way it feels to represent the content (Koch talks of meaning, which by his use is familiar to intentionality) of those states. In essence, Koch is saying (Im interpreting here, i COULD be doing itt wrong) that qualia are representational, and that it is vy virtue of that fact that they have a function. Now this is a thesis with a lot of philosophical baggage, but that I think is highly plausible. Koch mantains that the content of a quale is determined by the context (penumbra) in where the quale lies, This certainly seems right. The neural correlates of a quale would appear in the context of surrounding neural activity, and the interconnection between these systems would link qualia to its content (meaning). All of this, however, sidesteps the issue of in virtue of what properies does the penumbra, or the quale for that matter, represent anything at all. This is not the same as asking why qualia feel like anything at all, question that neither I nor Koch can answer. So although Koch's speculations are interesting, they fail to really explain anything at all, unless he gives us bridging principles. He tries, when he writes about how meaning arose out of sensimotor interactions, intermodality connections, or genetical predispositions. However, the details have to be inferred by the reader.
Koch is also highly simplistic in his dealing of split-brain studies. It is by no means obvious that splitting the brain means splitting conscousness. There is a whole book dealing with this issue (Alexanders tHE Unity of consicousness), and there are some good arguments that Koch ignores. (not to be blamed for he is a scientist.....he did start the speculation game, though)
So this book is a good review of the field, presents some novel ideas and interesting speculations. It is recomendable for novel readers, and a must have for cosnciousness fans. But I still wait for a landmark book, the Astonishing Hypothesis of the new decade. Koch is a wonderful writer and a brilliant scientist, and I do not doubt he will someday deliver.
Rating: 
Summary: A must read
Review: ABSOLUTELY RECOMMENDABLE for anyone interested in how the brain works.
The clear exposure and expertise of the author(s) makes of this book an extremely enjoyable read.
Great for Neuroscience and Cognitive science students. With citations supporting every little detail exposed, it creates a library for future readings.
For non-scientists interested in the brain and mind this book should be quite easy to understand.
Rating:
Summary: A must read
Review: ABSOLUTELY RECOMMENDABLE for anyone interested in how the brain works.
The clear exposure and expertise of the author(s) makes of this book an extremely enjoyable read.
Great for Neuroscience and Cognitive science students. With citations supporting every little detail exposed, it creates a library for future readings.
For non-scientists interested in the brain and mind this book should be quite easy to understand.
Rating:
Summary: A gripping quest
Review: Christof Koch takes the reader on a literal quest, starting where visual information enters at the eyes and proceeding as it is processed in successive layers of the brain, looking for the neural correlates of consciousness: neural activity corresponding in an explicit, easily understandable way, directly to our conscious percepts. Along the way we learn what is known (and what is still mysterious) about the various brain areas, neural organization, and information pathways, and about how this information has been gained. Understanding consciousness is a kind of holy grail, and the excitement of the author's personal chase rendered the book so gripping to me that I read it straight through.Many readers will find the most interesting sections to be those in which Koch goes beyond his more sober scientific publications to speculate on the nature of qualia, our sensations such as pain or redness, as arising through evolution and corresponding to "meaning". Unfortunately, beyond a few evocative paragraphs, Koch does not address the nature of meaning. He also explicitly defers judgement on questions such as why qualia feel like anything at all to us and whether we have free will. I don't think he should be faulted for these omissions -- while these subjects are not beyond the scope of science, they may well be beyond the scope of neurobiology. However, readers interested in the Quest for Consciousness will also enjoy What is Thought?, which brings ideas from computer science and other fields to bear on these questions. WIT? is organized around a computational theory of what meaning is and of how evolution discovers and exploits it. This theory suggests viewing the genome as source code that compiles into the brain as executable. Thus it is suggested that neurobiology is not the only or even the most straightforward path to understanding the mind: simple, understandable structure in source code often is blown up and obscured in the executable. What is Thought? analyzes computationally what it means to understand, how we understand, and what we can understand about understanding. Finally it offers a straightforward, principled theory of why qualia feel like something to us, and indeed why they feel like they do, as well analyzing in detail what free will is, how it arises, and what its limitations are. The computational theories of What is Thought? unify relevant data from a variety of fields but the book discusses relatively little neuroscientific data. Its theories and approach will ultimately be confirmed or falsified as technologic progress continues: as gene expression data and brain imaging improve, as new psychophysics experiments are developed, for example probing qualia illusions in unnatural circumstances. On my reading, they are consistent with the data and most of the theories in Quest for Consciousness, but also there is considerable potential for integrating the data and approaches of the two books into further experimentation and understanding.
Rating:
Summary: What causes consciousness?
Review: This is a great book that describes where we stand in the search for neuronal correlates of consciousness (NCC). The problem has been attacked by people from various different fields. Still, it has to be a biology problem. Consciousness clearly resides in the brain. If only we had plenty of examples of brain-damaged people ... some of whom clearly lacked consciousness, some who were almost conscious, some who were certainly conscious, some who were uncertainly conscious .... then maybe we'd work out what the key was. Luckily, we don't have all that many brain-damaged subjects.
Koch takes this sort of approach to the problem of discovering the NCC: he tries "to quantitatively correlate the receptive field properties of individual neurons to conscious perception." If there's no map between certain cells and the structure of a conscious perception, then it's unlikley that these cells are sufficient for that conscious percept. That means looking at what we'd normally think of as vision problems, optical illusions, attention loss, long and short term memory, and various automatic and semi-automatic responses to stimuli. What amazed me most was that the work on this subject is still easily readable by the layman.
One of the more interesting questions Koch raises is this: since consciousness resides in the brain, do we get two consciousnesses when we split the brain in two? Actually, (as Koch explains) this was studied by Roger Sperry, whose split-brain experiments on monkeys and other animals in the 1950s and 1960s showed that the two sides of the brain easily learn different responses to stimuli, indicating that these animals effectively possess two separate minds. There are, of course, as Koch describes, some human split-brain patients who also demonstrate this.
It's an interesting book that is easy to read. It's sobering to realize how little progress we've made on such a fundamental question.
Rating:
Summary: Simply Outstanding
Review: This is the best popular neuroscience book that I have read, and I've read a couple dozen of them over the last 15 years. I can say without hesitation that it rasies the bar for popular neuroscience writing.
It's not so much that Koch is the best writer, although he's very good. The strength of Koch here is that he provides a great deal of detail about the processes he talks about, and he organizes the information in such a way that you don't get lost in anatomical terminology. A lot of neuroscience books may such things as 'lesions in the posterior parietal cortex are known to be related to a condition called 'hemi-neglect' where the patient is unaware of objects in the left hemisphere, despite the fact they can see them if asked' - while that's interesting, it's usually presented as a brute fact with no real grounding of what the posterior parietal cortex does or how it fits into the larger scheme of sensory processing. But Koch does a marvelous job of explaining how various regions function and interconnect with others, and how that results in what you experience, or even what you don't experience.
The word 'quest' in the title isn't just hyperbole, you really are on an adventure to find something very specific, which is laid out at the beginning of the book. What Koch is looking for is what is called the Neuronal Correlates of Consciousness (NCC), meaning specific neurons whose activity can be demonstrated to be causally linked to specific aspects of conscious awareness (i.e. subjective experience). In this case, because more is known about the visual system than almost anything else about the brain, and certainly any other sense, he narrows his search for the NCCs to those that underlie visual experience.
So, in effect, this book is about the visual system, specifically how and where it generates conscious awareness of visual stimuli.
His quest starts at the retina, where you get a wonderfully detailed and readable account of it's structure and activity, then you are whisked down the optic nerve to the Lateral Geniculate Nucleus (another structure I've read about many times before, but have never come away with a clear understanding of what it does until this book). After that you travel to the back of the brain to areas V1-V4 in the visual cortex which break down the signals from the retina into bits and pieces of contrast, lines, angles, shading, dark and light, color. Koch swiftly moves up the processing hierarchy, moving from basic perceptual bits and pieces to object recognition and attention.
There is a revealing discussion of non-conscious visual processing that is compelling, giving the reader a glimpse of the enormous behind-the-scenes power that the brain brings to bear on perception, which we are fortuitously, and by design, never aware of.
There's a good deal of detail throughout, but never does he get bogged down. It's written with clarity and always with a sense of how it all fits into the quest for the NCC. He makes some surprising judgments about what neuronal activities qualify, or don't qualify as NCCs. And he's very honest and humble about what is known, what is theory, and what is conjecture.
This book stands out on its own merit, but the more curious reader may want to visit Koch's website at Cal Tech (http://www.klab.caltech.edu/cns120/) where you can watch streaming video from his lectures that are organized along the same outline as the book, each chapter is presented in a lecture. I greatly enjoyed watching the lectures as I made my way through the book, although I will emphasize again that the book is superb without the lectures (you won't get as much information from the lectures as the book), but having both was great fun.
I can't say enough good things about this book, it was captivating from the opening page to the last. Everyone who wants to know more about the brain and consciousness would do themselves a great service by reading it.
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