Idan Segev is a researcher out of standards

Our genome has evolved rapidly over time and this is still true today. This is why we decided to launch a research programme to simulate its operation on computer. "Idan Segev is a researcher out of standards. In addition to his offbeat Rolling Stones look, he defends projects really out of the ordinary. This specialist of neurosciences at the Hebrew University of Jerusalem began in mind to create a kind of artificial brain, built by connecting thousands of computers together. To a disbelieving audience, the mathematician-biologist household not his sentence. Come to Paris in a French Symposium on the brain, Idan Segev presented its "blue brain" project as a science fiction film. The scenario begins with a foolish bet. A team of Swiss and Israeli researchers decides one morning to model the inextricable network activity of neurons that make up the human brain. A colossal task that seems out of reach of existing techniques. As a first step, should just 10,000 processors connected in parallel simulation, what happens in a small sample of brain tissue. A column from a few millimetres cubic with 6 layers of neurons superimposed. Just a few thousands of nerve cells connected by 1 million connections. The first results of this challenge could be available in 2015. "It is that is the future of neuroscience", summarizes the researcher. But will wait a few more decades for the end of the story.

Behind this simulation lies a major question: what happens when an unexpected event changes the Organization of the network It is precisely what happens when a genetic mutation caused randomly changes the size or the Organization of the central nervous system. This is what has happened over the evolution. The human brain has gained weight and performance continued to advance. "5,800 Years ago, our ancestors began to write and paint. This phenomenon of the discovery of the art arrived suddenly. The same is true for the acquisition of language. "We questioned, this theory of the quantum jump is no unanimity within the scientific community. Many researchers looking for a progressive scenario, punctuated of successive developments and progress "by small keys."

Plastic body

Despite these controversies, Idan Segev is in consistent not. "The brain is an extremely plastic body that changes all the time." When you read a book or when is listening to a speaker, the brain networks reorganize permanently. A single mutation can lead to very rapid changes in the neuronal structure. "The brain of the mouse is the testing ground preferred neurologists. With its 40 million neurons, 2,000 times less than human, this mammal well unravel. In fact, more the size of the brain, it is the number of genes which intrigued scientists.

With its 25,000 genes, rodents are virtually equal game with humans (see illustration). "How is it that also minimal differences induce important functional differences", asked Jean-Pierre Changeux, key specialist of mental processes. In his view, the existence of single gene disorders (due to a single mutation in a single gene) is a beautiful working hypothesis. This is the case of microcephaly, which affects cell division and leads to the formation of small brains and mental retardation in humans. It is the deficiency of a single protein (NCDT) which is responsible for this deficit.

The birth, the human brain is very embryonic. "It's the postnatal development that makes a difference." "The brain of a newborn is 5 times lighter than adult brains (1)," said Jean-Pierre Changeux. More than half of synapses (2) are after the birth. This network is for the first two years of life, according to a process of creating random destruction poorly known. "A link which is not solicited is destroyed and, conversely, a used connection is reinforced," said neurologist of the Pasteur Institute.

Neurodegenerative diseases

It is this process of strengthening to acquire cultural behaviours such as reading or writing. "The activity of the network plays a critical role in the development," said the researcher. In other words, circuits which are not stimulated at the right time are eliminated. In fact, the nature considers that they are not useful and consume energy without any benefit to the organization. It can be eliminated without harming survival. The Salpétrière in Paris hospital, Alexis Brice works on the genetic basis of neurodegenerative disorders including Parkinson's disease.

The repetition of a particular sequence in a specific gene induces more or less late birth of the disease. "Overexpression of alpha-synuclein protein promotes the onset of the disorder and the number of copies determines the starting age," said researcher, who heads the Institute of neuroscience, Neurology and Psychiatry at the Parisian hospital. In North Africa, about 40 of some populations are carriers of the mutation. All do not develop the disease, which appears to confirm the existence of a protective gene unidentified. These individual mutations are yet explain everything. Arnold Munnich, Professor of Genetics at the Necker children ill in Paris hospital and specialist genetic diseases in children, the current craze for genetic testing is a dangerous folly. "Genetic tests seen flourish on the Internet are a hoax." In fact, the predictive power of these coarse analysis is very limited. However, this specialist predicted a bright future to these techniques when they are well supported by the medical world. "It is a very valuable to the diagnosis without being eugenics."