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Connectome: How the Brain's Wiring Makes Us Who We Are

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"Connectome", by Sebastian Seung is "One of the most eagerly awaited scientific books of the year ...intellectually exhilarating, beautifully written, exquisitely precise yet still managing to be inspirational". ("Irish Times"). What really makes us who we are? In this groundbreaking book, pioneering neuroscientist Sebastian Seung shows that our identity does not lie in our genes, but in the connections between our brain cells - our own particular wiring, or 'connectomes'. Everything about us - emotions, thoughts, memories - is encoded in these tangled patterns of neural connections, and now Seung and a dedicated team are mapping them in order to uncover the basis of personality, explain disorders such as autism and depression, and even enable us to 'upload' our brains. This book reveals the secrets of the brain, showing how our connectome makes each of us uniquely ourselves. "With the first-person flavour of James Watson's "Double Helix", "Connectome" gives a sense of the excitement on the cutting edge of neuroscience". ("New Scientist"). "Witty and exceptionally clear ...beautifully explained ...the best lay book on brain science I've ever read". ("Wall Street Journal"). "Seung is about to revolutionise brain science". ("The Times"). "The reader is swept along with his enthusiasm". ("The New York Times"). Sebastian Seung is Professor of Computational Neuroscience at MIT and an Investigator of the Howard Hughes Medical Institute. He has made important advances in robotics, neuroscience, neuroeconomics, and statistical physics. His research has been published in leading scientific journals, and also featured in "The New York Times", "Technology Review", and "The Economist".

384 pages, Paperback

First published January 1, 2012

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Sebastian Seung

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Displaying 1 - 30 of 179 reviews
Profile Image for Michiel.
387 reviews91 followers
July 17, 2013
This book was quite a pleasant read, especially compared to some of the other books on brain science I read. Seung gives a very clear and well structured overview of his ideas: from the concepts and principles of the connectome paradigm (basically the idea that a complete map of neuron wiring would allow us to completely understand the brain) to the techniques for constructing such a brain model to some philosophical consequences.

The reason that I give a relatively low rating is that I found the book quite full of 'hot air' (I also thought this of Seung's TED talk). Being a bioinformatician myself, I recognize the same type of hype that was around the human genome project. We can sequence a person for less than a year's wage, yet not all genetic diseases have been vanished from the face of the earth. Similarly, Seung does not really delve in detail how we will use the connectome to read memories or cure depressions. Though, this might be just me nitpicking.

It is also hard to take someone serious who 'mocks' genetics, but at the same time claims neural wiring is the holy grail to solve all of our eartly problems (literally).

On the whole this is an enjoyable book, but from a scientific point of view, it is a bit too 'shallow'. A better approach to brain science would be 'On Intelligence', at least IMHO.
Profile Image for David Rubenstein.
867 reviews2,789 followers
October 23, 2013
A connectome is the sum total of connections between neurons in a brain. Sebastian Seung argues in his book that one's connectome is the essence of an individual. A connectome contains one's memories and personality, and defines who we are. The idea is that at birth, one's neurons are connected with each another at random. As one grows, the brain's connectome changes through the "four R's": reweighting, reconnection, rewiring, and regeneration. These changes are the essence of growing new memories.

I found the first third of the book to be a bit boring, simply because I was already quite familiar with the subject from other books. Then, the book takes a different tack, emphasizing how important new technologies are to making new discoveries in science. This idea definitely resonated with me. Seung writes,
If you're a scientist who purchases instruments, you could strive for better ones than your rivals by excelling at fundraising. But you'd gain a more decisive advantage by building an instrument that money can't buy.

Seung describes a hierarchy of new technologies, each bringing new understanding to connectomes. He begins with the microscope, of course, but looking at pieces of a brain through a microscope is not very enlightening. The real ground-breaking technologies were various types of stains, such as the Golgi stain. This allowed researchers to identify individual neurons. Later, the electron microscope helped to analyze the structure of neurons, and imaging techniques like fMRI's helped to distinguish functional areas of the brain.
Human Brain Wiring
Seung is a leading researcher in the burgeoning field of connectomics in neuroscience. In the book, he emphasizes a host of new technologies that he hopes will eventually unravel the connectome of a mouse brain. First, new slicing techniques are being developed to peel off extremely thin slices of a brain. These slices can then be scanned by an electron microscope, whose depth of field is limited. The next technology is computer systems for handling massive amounts of data, in conjunction with artificial intelligence (AI) for discerning three-dimensional structure in a set of images. This section of the book is the most interesting, as the reader feels the enthusiasm of a researcher on a leading edge of science.

The last two chapters of the book are interesting speculations. One chapter is titled, "To Freeze or to Pickle?" It concerns new developments in cryonics, in which people elect to have their heads or their entire bodies frozen after death. The idea is that in the distant future it might be possible to revive the connectome in a brain, and thus revive a person from death.

The last chapter is about scanning connectomes to generate simulations of human behavior. Would such a simulation be an automaton, or would it have true feelings? And what, exactly, are feelings? If you enjoyed the movie "Matrix", then you will love this chapter.
Profile Image for Sheila.
Author 15 books171 followers
February 7, 2012
What makes us who we are? Think about that question for a moment...
...Among all of the questions we can ask as human beings, even with all of our progress and our potential, that question alone remains one of the most difficult, or perhaps the most difficult, to answer. Innumerable factors are involved when it comes to the inner workings of the mind and how it serves to shape our characters and our behavior. We are only just beginning to understand the unfathomable intricacies of the brain, this small, yet remarkably powerful organ at the center of all that we do. Our very functioning depends on it. Yet we understand relatively little about the relationship between the brain, with its vast network of neuronal connections, and the foundation of the genome, our genetic “program,” which possesses its own complex code.
That is about to change.
Of course, the genome serves as the foundation for many of our characteristics, such as our predisposition to various conditions and our physical attributes. It is the framework of our hereditary information, the core of traits passed on from parent to offspring, developed over many generations. However, the genome is not home to the memory of our first love or the feeling of pain when someone whom we know has been lost. It is not the center of our passion, nor is it the basis for our relationships with others. These are the qualities that make us truly unique. Every experience we have is linked to brain activity, specifically between neurons and synapses, which collectively might be thought of as the “circuitry” of the brain. The neuronal connections formed throughout our lives are now the subject of much investigation, because the relationships between these connections, now referred to as our “connectome,” may serve to tell us more about who we are and why than anything ever before. This is where our genome meets the brain's incredible system as it develops throughout our lives (relative, of course, to our personal experiences). Here, nature meets nurture to form the basis for what makes each and every person truly special. As they say, you are your Connectome.
Sebastian Seung is an ambitious and charismatic rising star in the field of neuroscience. He has received numerous accolades and currently teaches at MIT as a professor of computational neuroscience. Now, Seung, along with the help of fellow researchers, is determined to understand more completely the complexities of neuronal connections and their relationship to who we are. Connectome: How the Brain's Wiring Makes Us Who We Are is a lucid and exciting read about this exploration and the implications for truly solving this greatest of mysteries. Yes, it is a book about science, but this is not your ordinary science text. Seung, regarded as a highly effective and dynamic teacher, makes learning about the science of the brain enjoyable, and the content is accessible. You really get a sense of the potential regarding this research and what Seung and his colleagues hope to achieve through such discoveries. What would it be like to have a better grasp of the causes for conditions like schizophrenia and bipolar disorder?
In my opinion, this book is right for everyone, since it helps to illustrate the intricacies of our inner-connections and aids in giving us a clearer sense of why we are just as we are. But the book is strongly recommended for anyone with an interest in science (especially of the mind) and recent developments in the field of neuroscience. Connectome is also perfect for any reader with a genuine interest in learning more about the brain's impact upon our development as whole human creatures, with our capacity for both love and loathing, joy and chaos. Check out the following website for more information about the book and its author: http://connectomethebook.com/.
Profile Image for Mark.
1,177 reviews167 followers
May 22, 2012

Sebastian Seung is one of a group of neuroscientists who want to literally unravel the brain's wiring diagram in hopes that it will be the ultimate tool to determine our individual differences and to solve such deep and thorny problems as autism, schizophrenia, depression and other mental disorders.

Seung is a good writer, particularly at explaining the basics of neuroscience and helping you understand the history of research that revealed the existence of neurons, the development of brain maps and the discoveries of how certain parts of the brain specialize in certain functions.

The book is actually less successful, I think, when it delves into Seung's main interest -- figuring out how to trace the myriad connections of neurons and dendrites and neurites and synapses in the brain. He makes it clear how daunting the challenges will be in reconstructing a complete "connectome" of even one square millimeter of mouse brain, let alone a whole human brain, and is honest about how much further technology and computing power have to go to make that possible.

But he may be right in saying that the promise of connectomics is much greater than any other brain imaging and measurement method now available, all of which are leagues cruder by comparison.

The end of the book -- a speculative look at the possibilities of cryogenic preservation of the brain for future revivification, and the prospect for one day being able to "upload" the informational content of a brain into a computer program -- is meant to tantalize and raise some profound issues, but these are so far fetched at the moment they have a slight ring of absurdity.

That said, I thought this book had a lot to offer, and it certainly was the most accessible and deepest exploration of this field that I've encountered. Seung is also young enough that he may even see some of his connectome dreams come to fruition.
Profile Image for Daniel.
2 reviews
August 4, 2025
Tengo muchas cosas que decir sobre este libro, así que vamos a ir poco a poco. Lo primero de todo es que es recommendable para toda persona que quiera introducirse a la neurociencia porque presenta de conceptos de manera gradual y sencilla. Eso justo es lo que en mi caso, más he echado de menos. Falta profundidad en muchos de los conceptos explicados y que al final podrian ser sustituidas por gran parte del texto en los que el autor decide enrollarse en ideas abstractas y sin evidencia que, desde mi punto de vista, debieran unicamente comentarse en un capitulo final. Dicho esto, el nucleo principal del libro, la idea que a desarrollar por el autor me gusta y me parece curiosa, aunque de para poco más que para un par de capitulos (justo los centrales). En resumen, si lo que buscas es introducirte en el ambito de la neurociencia, este es tu libro. Si buscas un libro con mayor profundidad este libro se te queda corto.
Profile Image for Benedict.
4 reviews
August 30, 2025
The first chapters were nice: an accessible introduction to some core concepts of neuroscience and connectionism. The fascinating main idea of finding a connectome, and why this is challenging, was laid out well. But then the book lost me more and more. I found it to be lacking in focus, and therefore shallow. There are many digressions into philosophy and theology, and a lot of anecdotes, which would have made for an interesting chapter on their own, but in the way they were presented they were distracting. The last chapters about cryonics and uploading your identity lost me completely, as I felt they weren't saying much which hasn't been already explored in Sci-Fi literature. And while it's completely fine and interesting in my opinion to speculate about future developments in a science book, the overly self-confident tone of the author annoyed me at many points. Closing the book after the last chapter, I wasn't really sure what my main takeaways are.
Profile Image for Keith Swenson.
Author 15 books54 followers
November 12, 2020

Who are we? What are we? Dualists take the position that the mind is separate from the brain, while monists say they are the same thing. The connectome presents an intriguing third option: the mind is not the brain per se, but rather the way that the neurons are connected. Sebastian Seung presents this using everyday language, relating the effects to everyday occurrences and meaning. Your genes determine how your body grows from an egg to an adult. Your connectome is determined only partially by your genes, and quite a bit larger part by your experiences. It is almost a platitude: your experiences make you what you are, but in this book we have a clear explanation of why and how that works.

Part I starts by looking at the history of brain science. Phrenology, the study of the shape of the skull, is a largely discredited pseudoscience, but Seung teases us with the idea that phrenology at least promoted the idea that certain kinds of mental processing is associated with certain parts of the brain. Brain size has always been a historical fascination, but it is the structure that is important, not the size. Penfield's sensory homunculus maps specific sensory functions to specific parts of the brain. Phantom senses from amputated limbs can be found in this mapping.

Part II starts with the building blocks: neurons, how they function, how they grow, and most importantly how they connect. Seung's unconventional style leads us to the 'Jennifer Aniston neuron' which apparently we all have. It is a specific neuron that is triggered when we recognize Jennifer Aniston. Similar neurons exist for all other specific concepts that we have come to know. This brings him to an explanation of how memory works. Neurons are triggered or inhibited through their connections. The repeated firing of neurons at the same time cause neurons to create new synapses -- new connections that are the basis for long term memory. Learning is then simply the making of new connections between neurons. The way we perceive the world, and the way we remember what happened to us in the past, all comes from the pattern of connections between the neurons. The future of psychiatry is destined to be reduced to a new field called connectopathy: the ways that the connectome might be mis-wired.

However, connections are not simply binary on-off mechanisms. The connectome in changed through four different mechanisms which he calls the four R's of connectome change: reweighting, reconnection, rewiring, and regeneration.

Part IV shifts to more practical matters: how can we measure and study the connectome? He surveys the various means for solidifying the brain, slicing it, photographing, recognizing the structures, and tracing the path of nerves and how they are connected. For a worm with 302 neurons this has been done, but this is hardly a practical approach for humans-scale brains. MRI and other techniques allow studying living brains. It is all a bit too course grained for now, because while understanding the function of regions of the brain is important, it is the actual specific connections between specific neurons that form actual intelligence. Technology allow for increasingly fine observations, and increasingly massive data result sets, and it would appear that some day it may be possible to map your connectome.

Part V concludes the book with some interesting speculation that is sure to please the science fiction fans among us: can we achieve immortality through scientific means? First, can we freeze or pickle ourselves and be revived in the far future when death has been cured? Second, can we be uploaded to a software simulation of the brain. If the connectome can be fully traced in an individual, there is no reason that a simulation of the nerves would not produce a running facsimile of that individual with all their memories and skills. However, that copy of the person would be that: a copy, and not the original individual. It would make no sense to desire that a copy of ourselves achieves immortality, however some connectomes are wired to be insanely egocentric, and just might decide to do it anyway.

One tidy book brings us up to date on the state of neurology -- at least at a level that can be understood without a background in neurology. The book has to dispel a lot of myths and historical pseudoscience. It also makes it clear that we are still just at the beginning of the journey of understanding how the connectome achieves its most baffling result: a sense of consciousness.

Profile Image for Emanuela.
Author 4 books82 followers
September 7, 2016
Uno dei libri di neurologia più suggestivi che abbia letto.

Si parla di connessioni tra neuroni, quella ramificazione infinita di filamenti afferenti ed efferenti costituiti da dendriti e neuriti che, come spaghetti cotti in un piatto formano il groviglio che costituisce la massa cerebrale bianca e buona parte del SN periferico.
Secondo l'autore "noi siamo il nostro connettoma" perché, a differenza del DNA che determina con i propri geni la nostra costituzione e la stessa struttura del SN, le vie che si formano sono la componente plastica che si modifica continuamente per effetto dell'apprendimento di una vita.
Lo studio di come funzioni il sistema è complicatissimo ed altrettanto lo sono le indagini per sbrogliare quella immensa matassa, il cui sviluppo dipende da fattori funzionali ancora in fase di definizione, ma qualcosa comincia ad apparire all'orizzonte.

La prima parte del libro è una descrizione dettagliata della fisiologia che trova per il sistema di cablaggio del nostro SN alcune regole, leggi, che sono la Ripesatura, la Riconnessione, il Ricablaggio e la Rigenerazione (4R), che rendono questa sostanza estremamente dinamica sotto il profilo funzionale. E' importante avere abbastanza chiaro il funzionamento microscopico per intuire i processi che si esplicitano a livello macroscopico, come ad esempio, quello della memoria o della possibilità che la mappa corticale subisca variazioni di fronte a carenze percettive o motorie causate da traumi o patologie. Ma questo discorso vale anche per iper sollecitazioni di alcune funzioni.

Una sezione è dedicata alle tecnologie che aiutano i neurofisiologi a scoprire e mappare questo groviglio di strade, progetto che è immane se si pensa che, solo per ottenerlo da organismi relativamente semplici, ha richiesto anni di studio. Ma per fare questo si pensa ad un progetto come quello del genoma che sembrava impossibile da realizzare in pochi anni e, invece, la tecnologia lo ha permesso.

L'ultima parte tratta invece di come si stia tentando attraverso la strada della crionica (ibernazione), o quella del possibile tentativo dell' uploading della propria identità su un supporto informatico. Si parla quindi di "transumanesimo", condizione che trascende la condizione umana. Tutto ciò con inquietanti domande di natura etica e filosofica circa le conseguenze di queste possibili future pratiche.

Mi sento di commentare che la teoria connettomica, che privilegia la formazione di vie connesse ed estremamente interattive tra le diverse funzioni, a differenza di quella frenologica basata sulla mappatura della corteccia e la prevalente formazione delle sinapsi, mi affascina molto e dà ragione della propria individualità, della propria coscienza e della memoria, nonché, campo che mi interessa, dell'apprendimento. Ritengo che sia importante vedere in che termini il nostro SN agisca rispetto alle sollecitazioni interne ed esterne, di come, sia l'ambiente, sia di ciò che l'ambiente ha prodotto nella nostra mente, ci trasformi durante tutto l'arco della nostra vita.
Profile Image for Patrick.
193 reviews21 followers
July 14, 2012
amazon review:
We know that each of us is unique, but science has struggled to pinpoint where, precisely, our uniqueness resides. Is it in our genes? The structure of our brains? Our genome may determine our eye color and even aspects of our personality. But our friendships, failures, and passions also shape who we are. The question is: how?
Sebastian Seung, a dynamic professor at MIT, is on a quest to discover the biological basis of identity. He believes it lies in the pattern of connections between the brain’s neurons, which change slowly over time as we learn and grow. The connectome, as it’s called, is where our genetic inheritance intersects with our life experience. It’s where nature meets nurture.
Seung introduces us to the dedicated researchers who are mapping the brain’s connections, neuron by neuron, synapse by synapse. It is a monumental undertaking - the scientific equivalent of climbing Mount Everest - but if they succeed, it could reveal the basis of personality, intelligence, memory, and perhaps even mental disorders. Many scientists speculate that people with anorexia, autism, and schizophrenia are “wired differently,” but nobody knows for sure. The brain’s wiring has never been seen clearly.
.In sparklingly clear prose, Seung reveals the amazing technological advances that will soon help us map connectomes. He also examines the evidence that these maps will someday allow humans to “upload” their minds into computers, achieving a kind of immortality.
Connectome is a mind-bending adventure story, told with great passion and authority. It presents a daring scientific and technological vision for at last understanding what makes us who we are. Welcome to the future of neuroscience.
Profile Image for Steven Paglierani.
Author 9 books7 followers
April 11, 2012
Sebastian Sung is a brilliantly lucid writer. His analogies are clear; his ideas, interesting. Sadly his medical materialism taints the whole meal. According to Sung, there is no soul. Or anything else which can't be physically measured.

Most notably missing are any references to emergent properties. Nor does he refer to the idea that the knowable real world is based on naturally occurring fractal patterns, rather than on logically linear patterns. Worse yet, nowhere does he mention the idea that the only way to make real world measurements is with tipping-point based math. To Sung, simple counting math is enough.

Why give this book four stars then? Sung's explanations are amazingly clear. For this alone, this book should be required reading for anyone interested in neuro anatomy.

What about the fact that Sung believes the non material aspects of life all reduce to neurons?
Well, geniuses are allowed their biases. And Sung is truly a genius. Steven Paglierani
Profile Image for Cassandra Kay Silva.
716 reviews337 followers
February 17, 2013
I liked the writing in and of itself fairly well, the the premise the author was trying to sell did not quite come off. It's not even that in part I don't agree with him, its more that it should have been better developed and better researched to sway the audience. I just didn't feel that firing spark of joyful discovery that I had hoped to come across with this.
Profile Image for Rob Caswell.
137 reviews1 follower
June 19, 2025
This read was the next step in my continued exploration of contemporary ideas around consciousness. While this book certain touches on that, its primary focus is on the idea of the “connectome”, which is the unique “neuronal fingerprint” of any mind … basically a map of what neurons are connected to what.

I enjoyed the chapter on how thought memory functions… and the last two chapters, dealing with technical modes of immortality, were interesting. I found the middle of the book dragged… but that’s on me. The middle looks at the challenges, strategies, and technologies related to the quest to read and recreate a detailed human connectome. That’s spot-on for the book’s focus, but was an aside to my own reasons for picking up the book.

Overall it was fairly informative and interesting, though being published in 2012 it’s thoughts and statements on AI are notably out of date.
Profile Image for Igor Katselenbogen.
10 reviews
October 8, 2025
Appreciated the high level overview on matters behind brain functioning, almost perceived as motivational read. A lot of interesting facts and ideas. However, a big part of the book is dedicated to the history of the research advances in neuroscience that starts from far away times weren’t as exciting.
Profile Image for Skip (David) Everling.
171 reviews14 followers
February 15, 2012
An accessible book to introduce and help explain the exciting theory that the mind is entirely encoded in the particular architecture of your brain. The central theme of "Connectome" is that such a mapping of the connections between neurons provides a far more complete picture of mental activity than other brain models. As Seung explains, mapping a brain's connectome would enable highly specific examination and treatment of a brain, going so far as to allow correlation of neuronal activity patterns with memory and conscious experience itself.

The catch is the monumental technical challenge of obtaining and handling so much data, as mapping a connectome, like mapping a DNA genome, is a computationally expensive process. In fact, mapping the connections in a human brain is many, many orders of magnitude more complex given the density of neurons and the intricacy of their connections in brain tissue. Furthermore, technology with the proper specificity to automate the delicate task is still in early stage development. Thus a corollary theme in the book relates to the pace of technological change: the field of connectomics banks on the continuation of exponential growth in computer processing speed (e.g. Moore's Law) and accompanying technologies. Assuming that technology continues to progress as it has, Seung proposes that connectomes will naturally become the substrate of which we discuss our mental selves and our conscious identity.

Other notes:
The fundamental idea of the connectome is persuasive and fascinating, but perhaps because of such preexisting interests, this book was less in-depth than I was hoping for, and much of the content therein will be familiar to other fans of cognitive science or avid tech enthusiasts. Seung devotes the end of the book to the interesting future possibilities of cyber immortality, but they come with the usual speculation & caveats and don't yield much of a takeaway message. Seung's writing style is natural if not as crisp as a science journalist, just occasionally veering too folksy for the science (with a few awkwardly stilted metaphors).

I was originally introduced to Sebastian Seung's "Connectome" in his excellent 2010 TED Talk: http://www.ted.com/talks/lang/en/seba...
Profile Image for Gordon.
235 reviews49 followers
October 30, 2014
This is a very well-written book about a topic which, alas, I discovered just doesn't do very much for me. That said, if you're interested in a layman's description of how the brain works from the perspective of a neuroscientist rather than a psychologist, this is a great book.

Seung's thesis is that the brain is all about how it's wired, how it's connected. Two twins may have identical genomes, but differ from one another in skills and personality and other attributes because their differing environments and experiences and memories have caused their brains to be differently wired. "Wiring" in this case refers to the patterns of axons and dendrites and synaptic connections that enable neurons to signal each other and collectively create the mind.

The reason why Seung thinks that connectomics -- the science of the connectome -- is so interesting is because of its potential to change how we behave. Many things can go wrong with the brain: developmental disorders, strokes, traumatic injuries, psychosis, brain diseases such as Parkinson's and Alzheimers, and so forth. In order to cure or alleviate these, he believes that we must understand how the brain is wired. Then, we can look at how to change it, through the basic processes of reconnecting, reweighting, regenerating.

Unfortunately, the complexity of the brain's structure and processes are mind-boggling in their complexity. As a result, the science of the connectome is still in its infancy. We can't even see the connectome yet, let alone tinker with it in a predictable, effective way. Our interventions are still at a very gross level: with drugs, surgery, electro-stimulation, and the like.

So, while I admire the scientific brilliance of people like Seung, and appreciate his extremely lucid and readable prose, I think I'll check back in with this field in another 10 or 20 years when some more serious progress has been made. In the meantime, I'll stick to reading books about the brain from the perspective of psychologists, which I find considerably more accessible and of more immediate usefulness.
Profile Image for Karel Baloun.
516 reviews47 followers
January 24, 2017
Seung is a talented story-teller, weaving in history of science and famous ancient philosophers for a timeless feel, and also sharing the thrill of scientific discoveries and experiments. Connectome, as a craft of non-fiction, is polished to perfection.

His thesis is that each human being is no more and no less than the sum of the connections between all neurons, and all of the details in how these systems operate. And that this connectome is constantly updating itself until death, using the 4 R’s:

Reweighting means changes in the strengths of synapses.
Reconnection is the creation and elimination of synapses.
Rewiring is the creation and elimination of neural branches.
Regeneration is the creation and elimination of neurons

Isn’t it strange how 2010 (ted talk) and 2012 (book publication) feel like so long ago, here in 2017? His research does seem cutting edge, but also somewhat oddly isolated within his field, and the book probably already would benefit from an updated revision. For example, machine learning, convolutional neural nets, and deep learning have all tremendously advanced in 5 years, especially in serial image processing, so this must be aiding his work.

Nevertheless, many topics he approaches are thought provoking, and I’m sure this area of neurophysiology will become increasingly important.

The one area I wish he could have covered more is the role of various neurotransmitters or other molecules and proteins on rewiring and regeneration. Since he just left that area with “we don’t know how this works yet”, it seems research on cognition improving therapies is still far distant.

Lastly, I gave this a 4 since for me I wish he had ventured much deeper into the scientific details. This could well be a 5 for less technical readers who would love and enjoy his very lucid lay explanations of complex brain processes.
Profile Image for Chris.
130 reviews14 followers
July 3, 2015
I recommend this book to anyone interested in an approachable overview of a bit of the recent research on the structure of the brain. I've forgotten most of my high school biology, but that was not a problem.

I found the author's TED Talk on the same subject somewhat compelling, but really awkward. So, I was very happy to find the book very compelling, and only awkward when he kept coming back to examples featuring one particular celebrity.

The subtitle of the book ("How the Brain's Wiring Makes Us Who We Are") reads like a strong statement, but the author explains in the book that it is more of a conjecture, to be explored in the future.

This is not a book about the Human Connectome Project, which has had a fair amount of press, including pretty rainbow pictures of tiny "wires" flowing through the brain (the wires are graphs of differential water flow rates through the brain). That high profile project is using dMRI, which is a lower resolution, but complementary, technique compared with the techniques the author prefers to explore brains in high resolution (with electron microscopes).
Profile Image for Carol.
573 reviews11 followers
December 9, 2015
A connectome is a map of the connections of the neurons in the brain, Seung thinks that the variations within that framework is what makes us individuals. His descriptions of the brain and how it has been explored are very clear. I learned about axions and dendrites. synapsis and "gray matter" in the brain. He describes the brain like a very dense root system that is hard to decipher due to the complex way information is stored and exchanged across the brain. He says "you are your connectome. This expresses the idea that your personal identity is encoded in the pattern of connections between your neurons. If this hypothesis is true, then any kind of personal change is ultimately about changing your connectome." Being able to change is very important and sets us apart from computer programs that might simulate the brain. This book has given me a great deal of respect for the complexity and specialness of our brains. It is apparent that the study of the brain will occupy humans for a very long time!
230 reviews
March 19, 2018
"[...] you might act like a victim of brain damage. Neurologists know that such victims deny their problems. Amnesics, for example, sometimes accuse others of deceiving them when they have memory lapses. Stroke victims don't always acknowledge paralysis, and may contrive fantastic explanations as to why they cannot perform certain tasks."

"[...] since language itself is but a metaphoric expression of human experience."

"Perhaps we can resist "the devil" by restructuring our economic incentives, reforming our political systems, and perfecting our ethical ideals. These are the time-honored ways of improving our brains. But in time, science will also invent others. Bernal hoped that humanity would triumph over the world, the flesh, and the devil, which he called "the three enemies of the rational soul." We can express his dream in another way - as the quest to control atoms, genomes, and connectomes."

"Let's jump ahead for the moment to the last stage, human testing. Physicians manage this stage, administering candidate drugs to patients to see whether symptoms improve. It's neither economical nor ethical to test a drug on people unless there is already good reason to believe that the drug is likely to be safe and effective. Even so, nine out of ten candidates fail at this point, as I mentioned earlier, and the attrition rate is even higher for disorders of the central nervous system."

"Historically, most drugs have been discovered by chance."

"A few gulps of oxygen are all that stand between us and death."

"We do have an alternative to "hypothesis-driven," or deductive, research - the "data-driven," or inductive, approach. It too has three steps: (1) Collect a vast amount of data. (2) Analyze the data to detect patterns. (3) Use these patterns to formulate hypotheses."

""The greatest impact of genomics has been the ability to investigate biological phenomena in a comprehensive, unbiased, hypothesis-free manner." It doesn't sound like what we were taught about the scientific method in school, where we learned that science proceeds in three steps: (1) Formulate a hypothesis. (2) Make a prediction based on the hypothesis. (3) Perform an experiment to test the prediction. Sometimes that procedure works. But for every success story, there are many more stories of failure caused by choosing the wrong hypothesis to investigate. It can take a lot of time and effort to test a hypothesis, which might turn out to be wrong or - even worse - simply irrelevant."

"The outer gray matter is a mixture of all parts of neurons - cell bodies, dendrites, axons, and synapses - while the white matter contains only axons. In other words, the inner white matter is all "wires.""

"For example, the five broad classes of neurons in the retina - photoreceptors, horizontal cells, bipolar cells, amacrine cells, and ganglions cells [...]"

"And researchers can be distracted by the promise of AI, struggling in vain to fully automate tasks that would be more efficiently accomplished by the cooperation of computers and humans."

"[...] There exists no fair and certain method of doing science that can outperform the average."

"Military historians dwell on the cunning gambits of daring generals, and the uneasy dance of soldiers and statesmen. Yet in the grand scheme of things, such tales may matter less than the backstory of technological innovation. Through the invention of the gun, the fighter plane, and the atomic bomb, weapon makers have repeatedly transformed the face of war more than any general ever did."

"You might think that your hand grew fingers by adding cells. No - actually, cell death etched away at your embryonic hand to create spaces between your fingers."

"Since experiences like visual stimulation and exposure to language were normally available to all children throughout human history, brain development "expects" to encounter them, and has evolved to rely heavily upon them. On the other hand, experiences like reading books were not available to our ancient ancestors. Brain development could not have evolved to depend upon them."

"Amblyopia suggests that we are not simply born with the ability to see; we must also learn from experience, and there is a critical period for this process. If the brain is deprived of normal visual stimulation from one eye during this limited time window, it does not develop normally. The effect is irreversible in adulthood."

"As the saying goes, perfection is achieved not when there is nothing left to add, but when there is nothing left to take away."

"All human behavioral traits are heritable."

"There is good evidence, however, that retention of memories over long periods does not require neural activity. Some victims of drowning in icy water have been resuscitated after being effectively dead for tens of minutes. Even though their hearts had stopped pumping blood, the icy cold prevented permanent brain damage. The lucky ones recovered with little or no memory loss, despite the complete inactivity of their neurons while their brains were chilled."

"The ancients already knew the paradoxical fact that remembering more information is often easier than remembering less. Orators and poets exploited this fact in a mnemonic technique called the method of loci. To memorize a list of items, they imagined walking through a series of rooms in a house and finding each item in a different room. The method may have worked by increasing the redundancy of each item's representation."

"Nerve growth factor is one example; its discovery won Rita Levi-Montalcini and Stanley Cohen a 1986 Nobel Prize."

"In fact, a feeling of difficulty often accompanies the experience of memory, while perception usually feels effortless."

"You could think of the brain as being like our society, which abounds in conformists but also harbors some contrarians."

"I'll wager that even Pascal, with his depressive tendencies, would not have dreaded the forest of C. elegans."
Profile Image for Jessica.
Author 3 books25 followers
May 27, 2020
This book needed some heavy editing. It includes a profuse number of analogies and explanations to unrelated material that often made the neuroscience more difficult to understand and interrupted the flow. I know this is a book meant for laypeople but the analogies and metaphors were just too extravagant and sometimes led to totally unnecessary tangents, many of which digressed into issues of Christian theology.

It's also founded firmly in the medical model of disability in concern to autism and consistently references autism as a pathology to be cured - something that is totally at odds with the autism rights & neurodiversity movement.
2 reviews
March 28, 2015
Apt and succinct writing for such a profound and vast topic. Contains great and amusing references to philosophy and history combining science with art. A technical but otherwise informative book on the brain and its connections put in a simple manner for readers with basic biological knowledge to understand. Posits a great number of questions (More than answers) regarding the complex enigmatic mind.

Opens up the eye to the possibility of a future revolving around our connectome, Our self.

A thought provoking book worth the resd.
Profile Image for Sabin.
467 reviews43 followers
July 19, 2016
A cute little book in which Mr. Seung makes some bold claims wrapped up in a very accessible package. His insights come with a wealth of examples and explanations like the weighted voting system of neurons which is an approximation of the way neurons function to determine our actions.
All in all a very enjoyable book, which delves deep into the theoretical hypotheses under scrutiny at the moment in neuroscience, albeit in a very pleasant style.
Profile Image for Michael Durbin.
Author 4 books
October 11, 2013


Started great -- like one of the best science books for a general audience I'd ever read. Then it got tedious and even annoying, as when the author urged me to memorize a set of terms (frontal, temporal, occipital...) because he'd be using them a lot. Then he hardly did. I think the author forgot his audience, got a little sloppy, and maybe thinks just a bit too highly of his idea. Which I think is brilliant, by the way. I just didn't need the last 89% or so of this book.
Profile Image for Luiño Seoane.
6 reviews2 followers
March 5, 2015
Unluckily, the science of connectomics is still in its very beginnings so that the book cannot move much beyond speculation. There is a nice compendium of cutting-edge techniques in neuroscience and the book is very well written, which makes you wish for more. I personally was expecting astounding scientific breakthroughs, but soon realized that it is not the moment quite yet. I'd be very glad if the author would revisit the topic 10 or 15 years from now.
Profile Image for Nancy Stringer.
54 reviews20 followers
June 2, 2012
According to Sebastian Seung, the self is a non-material entity. The 21st-century soul, however, is not some strange ghost in the machine. It's information. You are, in effect, a piece of software running on the wetware in your skull.
Profile Image for Sergiy Kuzmenko.
25 reviews1 follower
February 1, 2014
The best thing I likes about this book is Sebastian Seung's reflections of philosophy and religion.
Profile Image for Gracie Clay.
8 reviews
January 10, 2025
I’ve wanted to read this book for years and found it a fascinating and frustrating read. I was eager to dig into the idea that the way our neurons are connected—the wiring of our brain or our “connectome”—“makes us who we are,” as the tagline of Connectome reads. I think the parts where Seung explains neuroanatomy, the types and inner workings of neurons and synapses, and complex ideas like the four R’s of connectome change (reweighting, reconnection, rewiring, and regeneration), Hebbian plasticity, and neural Darwinism were fantastic. I’m ok with the science being largely theoretical, as Seung makes clear that connectomics is in its infancy as a science, due largely to the massive undertaking it is to map an entire human brain coupled with barriers in the current technology.

However, the book as a whole fell flat for me. For one, Seung writes with frequent digressions and tangents that often made it hard for me to follow along or that simply weren’t that interesting to me. I think the entire two chapters about using connectomics as a means to achieve immortality through cryonics or “uploading” connectomes into a computer simulation could have been condensed into a paragraph or two, as the philosophical questions raised are worth mentioning, but I felt it unnecessary and indulgent to devote so much of the book to this topic.

Where Seung really lost me, though, was in his handling of neurodevelopmental disorders such as autism. Seung operates under an outdated and misguided view of such disorders, with statements that are often lacking in nuance or completely false such as that “most autistic adults are unable to function without some sort of supervision.” A lot of what Seung says veers into eugenics for me with how connectomics could be used in the prevention—and even the “repair” or rewiring—of such “connectopathies”. This is dangerous! Instead of acknowledging that different neurotypes exist and are valid in their own right, Seung seeks a cure for normal human variation. And even beyond my ethical concerns, from a purely scientific perspective, for an organ as complex as the human brain, it seems reductionistic to me to assume that there is one correct human connectome that all others should be judged—and modified—against.

Connectome was published over a decade ago, so I wonder if (and hope that) Seung’s views on this have changed and I’d be interested, in general, to read an updated edition of this book to see both how he would approach neurodiversity today and how far the research in connectomics has come since publication. Connectome introduces some really strong and fascinating concepts, and I’m on board with the idea and significance of the connectome. Where I think the book fails is in its applications. I believe the connectome can be used to validate and celebrate neurodiversity rather than silence and “cure” it, and I’d be much more interested to learn more about how knowledge of the connectome could support the living rather than immortalize the dead.
10.7k reviews34 followers
June 18, 2024
DOES THE TOTALITY OF CONNECTIONS BETWEEN NEURONS EXPLAIN US?

Hyunjune Sebastian Seung is a Korean-American scientist who is professor in computer science and neuroscience at Princeton University's Neuroscience Institute; previously, he worked as a professor in computational neuroscience and physics at the Massachusetts Institute of Technology.

He wrote in the Introduction to this 2016 book, “Studying an object as complex as the brain may seem almost futile… Only the most determined explorers can hope to capture a glimpse of this forest’s interior, and even they see it little, and see it poorly… even the humdrum lacks explanation. Every day we recall the pat, perceive the present, and imagine the future. How do our brains accomplish these feats? It’s safe to say that nobody really knows.” (Pg. xi) He continues, “This book proposes a simple theory: Minds differ because connectomes differ… Personality and IQ might also be explained by connectomes. Perhaps even your memories, the most idiosyncratic aspect of your personal identity, could be encoded in your connectome.” (Pg. xiv) He goes on, “In the pages ahead, I will present my vision for a new field of science: connectomics. My primary goal is to imagine the neuroscience of the future and share my excitement about what we’ll discover. How can we find connectomes, understand what they mean, and develop new method of changing them?... What do we already know, and where are we stuck?” (Pg. xix)

He explains, “a connectome is the totality of connections between the neurons in a nervous system. The term, like ‘genome,’ implies completeness. A connectome is not one connection, or even many. It is ALL of them. In principle, your brain could also be summarized by a diagram that is like the worm’s, though much more complex. Would your connectome reveal anything interesting about you?” (Pg. xiii)

He asks, “How could brains be so sophisticated when neurons are so simple? Well, maybe a neuron is NOT so simple; real neurons are known to deviate somewhat from the voting model. Nevertheless, a single neuron falls far short of being intelligent or conscious, and somehow a network of neurons is. This idea might have been difficult to accept centuries ago, but now we’ve become accustomed to the idea that an assembly of dumb components can be smart… it’s the organized operation of your billions of dumb neurons that makes you smart. This is the deepest question of neuroscience: How could the neurons of your brain be organized to perceive, think, and carry out other mental feats? The answer lies in the connectome.” (Pg. 59)

He says, “I’d like to propose that: ‘The function of a neuron is defined chiefly by its connections with other neurons.’ This mantra defines a doctrine I’ll call ‘connectionism.’ It encompasses both input and output connections. To know that a neuron does, we must look at its inputs. To understand the effects of a neuron, we should look at its outputs.” (Pg. 68)

He states, “Let me summarize the theory of recollection. Ideas are represented by neurons, associations of ideas by connections between neurons, and a memory by a cell assembly or synaptic chain. Memory recall happens when activity spreads after ignition by a fragmentary stimulus. The connections of a cell assembly or synaptic chain are stable over time, which is how a childhood memory can persist into adulthood. The psychological component of this theory is known as ‘associationism.’” (Pg. 73)

He comments, “the theory of all-to-all connectivity is flagrantly wrong. The brain is actually at the opposite extreme of SPARSE connectivity. Only a tiny fraction of all possible connections actually exist. A typical neuron is estimated to have tens of thousands of synapses, much less than the total of 100 billion neurons in the brain. There’s a very good reason for this: Synapses take up space, as do the neurites they connect. If every neuron were connected to every other neuron, your brain would swell in volume to a fantastic size.” (Pg. 86)

He suggests, “Synapse creation alone… would eventually lead to a network that is wasteful. In order to economize, our brains would need to eliminate the new synapses that aren’t used for learning… You could think of this as a kind of ‘survival of the fittest’ for synapses. Those involved in memories are the ‘fittest,’ and get stronger. Those not involved get weaker, and are finally eliminated… In other words, synapse creation is, a ‘dumb,’ random process that endows the brain only with the POTENTIAL for learning. By itself, the process is not learning…” (Pg. 88-89)

He summarizes, “I’ve talked about four types of connectome change---reweighting, reconnection, rewiring, and regeneration. The four R’s play a large role in improving ‘normal’ brains and healing diseased or injured ones. Realizing the full potential of the four R’s is arguably the most important goal of neuroscience… In principle we should be able to promote the four R’s through artificial means, by manipulating such molecules… But the four R’s are also guided by experiences, so finer control will be achieved by supplementing molecular manipulations with training regimens.” (Pg. 131-132)

He acknowledges, “My emphasis on structural criteria for dividing the brain will seem strange to a contemporary neuroscientist, who is used to combining them with functional criteria. But this kind of emphasis is commonplace in the rest of biology. The organs of the body were known as structural units long before their roles were understood, and can be identified by a naïve observer with no knowledge of function.” (Pg. 183)

He concludes, “Over the past few centuries, science has shaken our belief in the soul…. According to this doctrine of materialism … Your atoms… obey the same laws as all other atoms in the universe… Your body and brain are not fundamentally different from the artificial machines manufactured by humans, only much more complex. But computers have forced us to reexamine the doctrines of materialism and mechanism… You are neither machine nor matter. Those are just means of storing what you really are---information.” (Pg. 270)

He ends by saying, “The ‘meaning of life’ includes both universal and personal dimensions. We can ask both ‘Are we here for a reason?’ and ‘Am I here for a reason?’ Transhumanism answers these questions as follows. First, it’s the destiny of humankind to transcend the human condition… Second, it can be a personal goal to … use technology to otherwise improve oneself. In both of these ways, transhumanism lends meaning to lives that were robbed of it by science. The Bible said that God made man in his own image… The transhumanists say that humanity will make itself into God.” (Pg. 273)

This book will interest those seeking novel ideas about the brain.


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