September 15, 2014

Sci + Tech | February 3, 2014
Signatures of consciousness
Opening the door to the human mind
Written by | Visual by Alisa Brandt | The McGill Daily

Human curiosity about the nature of its own conscious experience is not new. The problem seems as old as human thought. Throughout the ages, philosophers and scientists have been, above all, intrigued by the unique and non-transferable nature of the human mind and amazed by the elusiveness of this phenomenon. For a long time, we thought such a complex matter escaped the possibility of being scientifically addressed. If science measures and analyzes objective events, then how could this subjective topic be a part of its inquiry?

Even though, historically, society has been inclined to believe in a ‘separate’ soul, apart from the physiological processes of the body, currently most people in different fields accept the fact that the mind arises from the physiological processes occuring n the brain. Before the 1970s, scientists did not dare raise this topic. Nowadays, thanks to new brain-imaging technologies, they are beginning to make progress in a field that used to belong exclusively to philosophers. This is how Stanislas Dehaene, a professor at the Collège de France, started his talk on “Signatures of Consciousness in the Human Brain” at the Institut Universitaire de Gériatrie de Montréal.

So, how to study consciousness? Many theoretical approaches have attempted to answer complex questions like what it is or how and why our sense of self originates. For this so called “hard” problem of consciousness, Dehaene thinks a better comprehension of the phenomenon will emerge from its decomposition into smaller, simpler questions, addressable by minimal experimental paradigms. When it comes to more abstract philosophical problems, he believes we need a much better definition before experimenting with them.

By comparing conscious and non-conscious brain states (using brain imaging methods such as functional magnetic resonance imaging or electroencephalography that allow us to see the living, acting brain), researchers have been able to identify the functional changes that underlie conscious experience.

Dehaene’s approach is based on the “workspace-model theory,” proposed by Bernard J. Baars in his book, A Cognitive Theory of Consciousness. According to this model, consciousness is the ability to share information from inside a module to the rest of the brain. By comparing conscious and non-conscious brain states (using brain imaging methods such as functional magnetic resonance imaging or electroencephalography that allow us to see the living, acting brain), researchers have been able to identify the functional changes that underlie conscious experience. These are the so called “signatures of consciousness.” This has special relevance when it comes to potential clinical applications. For example, looking for these signatures could help us to detect consciousness in a patient that does not have the ability to communicate due to brain damage.

The question of the social and cultural context of our conscious experience has also been of interest to neuroscientists. “[Our lab] tries to study the most basic aspects of consciousness […] But I am also personally interested in how you perceive digits and words. These are of course enormously influenced by culture; we can only recognize them because we have gone to school.” Dahaene went on to illustrate the example of school as an external influence on our brains by explaining how the processing of faces is moved from the left hemisphere to the right when we learn to read, so visual processing of words takes the place in the brain where faces used to be.

Although some philosophers or anthropologists may accuse these kind of models of being reductionist, Dehaene asserts that “reductionism” is a not an appropriate word for science. “The way science deals with problems is by decomposing a system,” he said, “But it is not as if we wanted to jump from the molecular mechanisms or a single neuron property all the way to consciousness. We need intermediate conceptions and intermediate descriptions, possibly of a mathematical nature.”

“What needs to be addressed now is the system of communication which allows these results to be shared. If we can implement this in a machine, I think we would all agree that we can call it consciousness.”

Another of Dehaene’s claims is that it is possible to build simulations of neural networks that, when put together into a neural architecture with long distance connections, can reproduce the signatures of consciousness. When asked if he believes this may mean that we will one day build machines that we can call “conscious,” he declared that he doesn’t see any reason why this should be impossible. “Of course, our current simulations are way too simple. Nowadays, we program computers in a completely modular manner. We already have highly specific models for face or speech recognition, so we have already solved a number of the ‘modular’ problems of the brain. What needs to be addressed now is the system of communication which allows these results to be shared. If we can implement this in a machine, I think we would all agree that we can call it consciousness.”

Despite the fact that his team has already found brain correlates of conscious events, there are still a lot of things to be done. According to Dehaene, the future lies in decoding brain representations instead of just detecting them. This would have a major clinical implication: it would allow non-communicative patients to express themselves through a machine interface. The challenge is complex: It implies we will be able to reconstruct a person’s mental image from the physical patterns of activation in a brain. Researchers are slowly working toward this goal – Dahaene’s research team has already studied brain activity underlying the processing of numbers. He claims that they have been able to infer the number a patient is thinking about and guess it correctly in more than 50 per cent of situations – which is better than mere chance.

The topic of consciousness is currently highly debated, but there’s no doubt that the advances in brain research bring us closer to a physiological understanding of what we call “consciousness.” Intense discussions on this highly contentious topic are currently on the table and there are still a lot of thinkers that believe in a more complex interdisciplinary approach to the subject. Many people would disagree with views that machines will someday be conscious or with Dehaene’s claim that “It is the end of the time of philosophy for consciousness. It is now an experimental science in all of its aspects.” We don’t know if time will prove him right or wrong, but with continued experimental study, the once closed door of human consciousness is slowly being opened.

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