Les neurosciences explorent notre univers intérieur
Wolf Singer est un éminent spécialiste des neurosciences. Il est directeur de l’Institut Max-Planck pour la recherche sur le cerveau de Francfort et il est très soucieux de communication. À l’inverse des physiciens du CERN, qui construisent des détecteurs au câblage très complexe pour étudier les collisions de particules, Singer, avec ses collègues, essaye de décoder la dynamique du «câblage» du cerveau, où quelque 1011 neurones sont reliés par 1014 «fils». De plus, la recherche montre à présent que l’ensemble constitue un système très réparti sans gestion centrale. À l’occasion d’une visite au CERN, Singer évoque avec Carolyn Lee ses recherches sur les mystères du cerveau, et sa passion pour la communication.
When physicists at CERN try to understand the basic building blocks of the universe, they build gigantic detectors – complex, intricately wired instruments that are capable of measuring and identifying hundreds of particles with extraordinary precision. In a sense, they build "brains" to analyse the particle interactions. For prominent neuroscientist Wolf Singer, director of the Max Planck Institute for Brain Research in Frankfurt, the challenge is quite the opposite. He and other researchers are trying to decode the dynamics of a mass of intricate "wiring", with as many as 1011 neurons connected by 1014 "wires". The brain is the most complex living system, and neuroscientists are only beginning to unravel its secrets.
Until recently, according to Singer, the technical tools available to neuroscientists were rather primitive. "Until a decade ago, most researchers in electrophysiology used handmade electrodes – either of glass tubes or microwires – to record the activity of a single element in this complex system," explained Singer. "The responses were studied in a meticulous way and it was hoped that a greater understanding would arise of how the brain works. It was believed that a central entity was the source of our consciousness, where decisions are made and actions are initiated. We have now learned that the system isn’t built the way we thought – it is actually a highly distributed system with no central coordinator."
Myriads of processes occur simultaneously in the brain, computing partial results. There is no place in this system where all of the partial results come together to be interpreted coherently. The fragments are all cross-connected and researchers are only now discovering the blueprint of this circuitry.
This mechanism poses some new and interesting problems that have intrigued Singer for many years. How is it possible for the partial results that are distributed in the brain to be bound together in dynamical states, even though they never meet at any physical location? Singer gives the example of looking at a barking dog. When this happens, all 30 areas of the cerebral cortex that deal with visual information are activated. Some of these areas are interested in colour, some in texture, others in motion and still others in spatial relations. All of these areas are simultaneously active, processing various signals and applying memory-based knowledge in order to perceive a coherent object. A tag is needed in this distributed system at a given moment of time so as to distinguish between the myriads of neurons activated by a particular object or situation, and those activated by simultaneous background stimuli. In 1986 Singer discovered that neurons engage in synchronized oscillatory activity. His hypothesis is that the nervous system uses synchronization to communicate.
Singer stresses that researchers in his field are closer to theorists in high-energy physics, because the tools necessary to decode the large amount of data generated by the brain’s activity do not exist yet. "This morning when I toured the ATLAS experiment, I heard how the data generated at the collision point is much richer, but physicists use filters to extract the most interesting data, which they formulate in highly educated ways," said Singer. "The amount of data generated by the sensory organs is more than the brain could digest, so it reduces redundancy. Due to this enormous amount of data, the brain, by evolution, developed a way to filter it all. The most important information for us is based on survival, such as where food can be found or how our partners look."
Brain function and communication
Singer began his career as a medical student at the Ludwig Maximilian University in 1962 in his hometown of Munich. He was inspired to specialize in neuroscience after attending a seminar by Paul Matussek and Otto Creutzfeldt, who discussed schizophrenia and "split brain" patients. After his postgraduate studies in psychophysics and animal behaviour at the University of Sussex, he worked on the staff of the Department of Neurophysiology at the Max Planck Institute for Psychiatry in Munich and completed his Habilitation in physiology at the Technical University of Munich. In 1981 he was appointed director at the Max Planck Institute for Brain Research in Frankfurt and in 2004 he co-founded the Frankfurt Institute for Advanced Studies.
The 20th century brought many advances in fundamental physics, including the discovery of elementary particles. During this same period, neuroscience provided greater illumination of the brain’s functions. One of the most significant is the identification of individual nerve cells and their connections by Camillo Golgi and Santiago Ramón y Cajal, winners of the Nobel Prize for Medicine in 1906. Another important advance was the introduction of the discontinuity theory, which regards neurons as isolated cells that transmit chemical signals to each other. This understanding allowed neuroscientists to determine the way in which the brain communicates with other parts of itself and the rest of the body.
Some of the results of the first studies of the relationships between function and the different areas of the brain were made using patients injured during the First World War. Later, with the discovery of magnetic imaging to study brain function, researchers were able to turn to non-invasive methods, but there is still much more development needed. With procedures such as magnetic resonance imaging, a neurologist can find out where a signal originates; but the signal is indirect, coming from the more oxygenated areas. A magnetic field of 3 T applied to an area of a square millimetre can show which part of the brain is activated (e.g. by emotions and pain) and reveal the various networks along which the signals travel.
At the same time, neuroscientists are trying to decode the system and explain how biophysical processes can produce what is experienced in a non-material way – a meta-to-mind kind of riddle – with new entities and the creation of social realities such as sympathy and empathy. This is leading to a new branch of neuroscience, known as social neuroscience.
In other research, colleagues of Singer are studying the effects of meditation on the brain. They found that it creates a huge change in brain activity. It increases synchronization and is in fact a highly active state, which explains why it cannot be achieved by immature brains, such as in small children. Buddhist monks use their attention to focus the "inner eye" on their emotional outlet and so cleanse their platform of consciousness. In 2005 Singer attended the annual meeting for the Society of Neuroscience in Washington, DC, together with the Dalai Lama. Their meeting resulted in discussions about the synchronization of certain brain waves when the mind is highly focused or in a state of meditation.
Singer is also no stranger to controversy. His ideas about how some of the results of brain research could have an impact on legal systems caused a sensation in 2004. His theory that free will is merely an illusion is based on converging evidence from neurobiological investigations in animals and humans. He states that in neurobiology the way in which someone reacts to events is something that he or she could not have done much differently. "In everyday conditions the system is deterministic and you want your system to function reliably. The system is so complex and we are constantly learning new things," explained Singer. There are many factors that determine how free someone is in their will and thinking. Someone could have false wiring in the part of the brain that deals with moral actions, or perhaps does not store values properly in their brain, or could have a chemical imbalance. All of these biological factors contribute to how someone reacts in a given situation.
Singer feels strongly that the general public should be aware of what scientists are working on and that enlightenment is essential. "Science should be a cultural activity," he said, adding that in society the people who are considered "cultured" generally are knowledgeable in art, music, languages and literature, but not well versed in mathematics and science.
In 2003 he received the Communicator Prize of the Donors’ Association for the Promotion of Sciences and Humanities and the Deutsche Forschungsgemeinschaft in Germany. Communicating his passion to the young has been a challenging and yet highly rewarding experience. He works to engage society in discussions about the research in his field, providing greater transparency and comprehension. His dedication to improving communication between scientists and schools is evident in the programme that he has initiated: Building Bridges – Bringing Science into Schools. This creates a stronger dialogue between scientists, students and teachers. • For Wolf Singer’s colloquium at CERN, "The brain, an orchestra without conductor", see indico.cern.ch/conferenceDisplay.py?confId=26835