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Wednesday, March 24, 2010


Firing on all neurons: Where consciousness comes from

Consciousness is one of neuroscience's long-standing mysteries. At its most basic, it is the simple question of why we become aware of some thoughts or feelings, while others lurk unnoticed below conscious perception. Is there a single module in the brain, a "seat of consciousness" if you like, that is responsible for awareness? Or is it a result of more complicated activity across a number of brain regions? Solve this, and we may be a little closer to explaining the more esoteric aspects of our complex internal experience.

Now one theory that claims to do just that is rapidly gaining weight, with strong evidence from research such as Laureys's to back up its predictions. The idea, dubbed the global workspace theory, was first floated in 1983 by Bernard Baars of The Neuroscience Institute in San Diego, California. He proposed that non-conscious experiences are processed locally within separate regions of the brain, like the visual cortex. According to this theory, we only become conscious of this information if these signals are broadcast to an assembly of neurons distributed across many different regions of the brain - the "global workspace" (see diagram) - which then reverberates in a flash of coordinated activity. The result is a mental interpretation of the world that has integrated all the senses into a single picture, while filtering out conflicting pieces of information (see "Neural conflicts").

Stanislas Dehaene of the French National Institute of Health and Medical Research (INSERM) in Gif sur Yvette and Jean-Pierre Changeux of the Pasteur Institute in Paris updated Baars's model with the latest findings on the brain's wiring. Dehaene's group had already shown that distant areas of the brain are connected to each other and, importantly, that these connections are especially dense in the prefrontal, cingulate and parietal regions of the cortex, which are involved in processes like planning and reasoning.

Will thinking machines need bodies?

If our ability for abstract thought is closely tied to our physical selves (see main story), will intelligent machines also need bodies?

It is a question that is being investigated. Roboticist Josh Bongard at the University of Vermont in Burlington says that the physical bodies of robots and the way that they interact with the environment might be key to creating the capability for intelligent, abstract thought. For a start, Cynthia Breazeal at the Massachusetts Institute of Technology and her team has already created anthropomorphic robots that use knowledge of their own bodies to infer the mental states of humans

Mind over matter? How your body does your thinking

Lakoff reckons that the volunteers are making use of two sets of metaphors for imagining numbers: that up is more and down is less, and that right is more and left is less. Such metaphors would have been learned and hard-wired into the brain at a young age. A child watching a glass of water being filled up, or building blocks piled up, will learn that increasing height means greater quantity, for example. Separate brain regions that process quantity and height could then have been linked up in the growing brain, he says, leading to a hard-wired understanding of the metaphor that up is more. Similarly, right-handed people may learn to link right with more because that hand is dominant for them.

What's not clear from Loetscher's experiment, however, is if eye movements are driving the number selection, or if the number selection triggers particular eye movements.

To probe whether movements can drive thought, Daniel Casasanto of the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands, turned to the metaphors that we use to speak of our moods. "We can hardly help mapping them onto a vertical, spatial schema, with the good end 'up' and the bad end 'down'," says Casasanto. "We talk of being high on life, or our mood taking an upswing, or feeling down in the dumps."

"The brain sends an endocrine signal to the pituitary gland. This makes protein hormones which reaches the ovaries and testes," Plant says.

It all begins with a kiss -- the KiSS 1 gene, which produces a protein in the hypothalamus. When the protein connects with its receptor, the GPR54 gene, puberty begins.

Dr. Plant says this is the first real handle we've had on the issue of the trigger. With wide variation, that trigger is pulled sometime between ages 10 and 16. But early or late puberty can pose developmental problems, like behavior problems and low self-esteem. Pediatricians have to treat these children with either precocious or delayed puberty.

Around 1965, a schism developed between the peacock mods (also known as smooth mods), who were less violent and always wore the latest expensive clothes, and the hard mods (also known as gang mods), who were identified by their shorter hair and more working-class image.[7] Also known as lemonheads and peanuts, these hard mods became commonly known as skinheads by about 1968.[8] Their shorter hair may have come about for practical reasons, since long hair can be a liability in industrial jobs and a disadvantage in streetfights. Skinheads may also have cut their hair short in defiance of the more middle class hippie culture popular at the time.[9]

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