Thursday, February 09, 2012

Book Review---- Connectome: How The Brain´s Wiring Makes Us Who We Are by S. Seung

Sebastian Seung, a young and bright neuroscientist based at MIT, uses a colourfull metaphor to describes the brain.

He compares the brain with a forest, a magic forest, and its special cells, called neurons, with enchanted branches.

Also compares neuroscientists, scientists dedícated to the study of nervous systems, with explorers.

He does so in his new book entitled “Connectome: How The Brain´s Wiring Makes Us Who We Are” where presents to a wider audience the science of connectomics and the idea of connectome.

For neuroscientists to understand the brain is all a matter of connections. And understanding connections lead to understand the self, the connected self.

A connectome is the totality of connections between neurons in a nervous system and connectomics the scientific study of all those connections.

Like explorers who want to find new roads, new paths, in foreign and not yet known forests, neuroscientists want to reveal how the brain is made up of billions of seeds planted at once, say neurons, and the millions of connections between them.

The word connectome shares a family resemblance with genome and connectomics with genetics or genomics.

But unlike genomes fixed from the moment of conception which hasn´t changed since you were born our conectomes change with experience.

The kinds of changes suferred by our connectomes are sumarized by the four Rs (reweighting, reconnection, rewiring, regeneration).

The purpose of neuroscience is to tap the four Rs to understand better the operations of the brain which in turn would produce the mental functions necessary for every inteligent behaviour.

If Genomes are the entire unidimensional sequence of molecules known as nucleotides and denoted by the letters A, C, G,T. connectomes are the entire patterns of connections within the brain viewed as networks or an entangled web much like the Internet.

The big hypothesis underlying the book is that you are more than your genes, you are your connectome.

According to an alternative theory individual differences, how tall you are, what personality traits you have… depend on genes. You are unique because your genes differ from those of other individual.

In Sebastian Seeung opinion what makes you, you, is your connectome or the wiring diagram of your brain.

What makes us unique is the way the pattern of connections differ from brain to brain. Connectopaties are the way in which brains are wired in a less than ideal form and then looking for the anormal connections can shed light onto human mental disorders.

In part I, Sebastian Seung recounts mayor hints in the history of neuroscience explaining traditional strategies used in neuroscience to understand what makes us unique. Here Dr. Seung refers to the principle of localization and the doctrine of connectionism

Localizationism states that different regions of the brain subserve different mental functions and it was proved by the lesion approach when neurologists found cases of people having brain injuries causing them behavioural or cognitive impariments.

Famous is the discovery of the language production area in the lft hemisphere of the brain by Paul Broca.

Broca examined a patient nicknamed Tan becasue he only was capable of uttering the word Tan!. When the patient died from an infection Broca Studies his brain and notice that he lacked an entire patch of he brain in the left temporal lobe.

The day after he report to the Anthropological Society having found the language area.

This strategy is known as the localization approach and although it has been productive we know now that some areas can perform more than one mental function and on the contrary two distinct regions can perform the same mental function.

In other words, there is no one-to-one corresponden among brain areas and mental funcions.

This lead neuroscientists to shift attention from localization to organization. It is possible after all that what matters for mental function is not which area performs what function or what size has but how that area is connected to other areas.

Its the organization what matters not the size or number of synapses and neurons. And here comes into the scene the idea of a connectome.

In part II, Seung introduces the forerunner for the idea of connectome the intelectual traditión dating back to the nineteenth century and still evolving known as the doctirine of connectionism, the idea that connections is of paramount importance for mental function.

In Part III, Sebastian Seung talks about the connectomes and its relation with genes.

In Part IV shows how important is the discovery of new technologies for science and in particular for the field of connectomics.

The success of connectomics depends on the ability of computers and machines to detect neurons at high speed. Remember that the human brain contains millions of neurons and the task of counting neurons perform by humans is unsourmontable.

The field of automating image analysis and machine learning are indispensable for this endevour.

Also how the prospect of finding drugs to treat conectomes gives hope to cure human mental disorders such as autism, schizophrenia or depression.

Part V, ends the book arguing about the possibility of reshape connectomes, changing brains, and therefore, transform humans for the better.

In essence, Sebasian Seung´s book is a journey throught out the frontiers of neuroscience about what makes human uniquiness, and a plausible answer to know where our identity resides is in our connectomes.

1 comment:

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