Are babies conscious? And at what age-- twelve months? Five months? Could they already be conscious in the womb? This may not be as far-fetched as it seems, according to Dehaene. The cortex, the epicenter of human consciousness, starts to form by six months gestation. Neuroscientists suspect from studies that even within the womb, in the late stages of pregnancy, the fetus becomes familiar with the sound of its mother's voice and may already be learning language. While it's impressive that a fetus responds to the sounds of its mother's voice while still in the womb, Dehaene points out that the brain can process language without consciousness.
Dehaene believes that consciousness emerges from what he calls, 'the global neuronal workspace' in the brain. It is a workspace that generates consciousness when the different parts of the brain engage and communicate with each other at a high level.
But there is a threshold of activity that has to be crossed before tests can demonstrate actual conscious perception. Beneath this threshold there is evidence of information processing--but without the test subject showing signs of being aware of it. While consciousness and the mind are big topics in philosophy, they tend to be treated in abstract terms, Dehaene says, and in his view philosophers of mind do not engage enough with the ability of neuro-imaging technology to tell us more about how our brains work when we are conscious.
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In his book, Consciousness and the Brain , Dehaene explained how his dissatisfaction with the philosophical approach to studying subjective consciousness was a factor in inspiring his experiments. To pin down consciousness in the lab, you need to catch it in the act of access to an event or process. And for Dehaene this means engaging the test subject in a way that unambiguously reveals conscious action--for example, by reporting or indicating that they can visually make out an image flashed on a screen.
The advantage of the former, is more refined 3-D detail of the location of activity in the brain, while the advantage of EEG is better recording of the brain's electrical activity in real time. In other words, the brain crosses a threshold, he said, when the test subject's exposure to the image is long enough.
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Very short exposure, under milliseconds, reveals a base level of activity on EEG, indicating the brain is processing the information. But the subject does not indicate awareness. But at longer duration, between ms and ms, for example, something dramatic occurs--multiple parts of the brain 'light up' and the test subject indicates his or her awareness of the image, either by pressing a button or vocally reporting so. Once he was able to establish this marker, Dehaene and his team decided to do the same tests in infants. This involved several experiments with newborns, ranging between five months and twelve months of age, to measure precisely whether their brains evince the same indications of consciousness as adults do in similar tests.
In infants, of course, the scientists could not count on any verbal response. The face is very attractive to infants, so we knew they would be attracted to that. So for even a short duration you get a little bit of activation; a little bit longer you get a bit more activation. But as they lengthened the duration of image exposure, they saw emerge the same non-linear phenomenon as they had seen in adults: a late slow wave on the EEG showing a nonlinear profile lighting up at the expected perceptual thresholds.officegoodlucks.com/order/34/578-como-rastrear.php
Scientists Closing in on Theory of Consciousness
To be sure, Dehaene and his team noted the infants responded more slowly than adults: In five-month-old infants, at around ms the brain activity crossed the threshold and the child's face turned toward the image. In older infants, of twelve months, they reacted more quickly, around ms. Scientists now reject the latter idea, but some thinkers still support the notion that the mind is somehow removed from the physical world. But while philosophical approaches can be useful, they do not constitute testable theories of consciousness, scientists say.
In the last few decades, neuroscientists have begun to attack the problem of understanding consciousness from an evidence-based perspective. Many researchers have sought to discover specific neurons or behaviors that are linked to conscious experiences. Recently, researchers discovered a brain area that acts as a kind of on-off switch for the brain.
When they electrically stimulated this region, called the claustrum, the patient became unconscious instantly. In fact, Koch and Francis Crick, the molecular biologist who famously helped discover the double-helix structure of DNA , had previously hypothesized that this region might integrate information across different parts of the brain, like the conductor of a symphony.
But looking for neural or behavioral connections to consciousness isn't enough, Koch said. For example, such connections don't explain why the cerebellum, the part of the brain at the back of the skull that coordinates muscle activity, doesn't give rise to consciousness, while the cerebral cortex the brain's outermost layer does.
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This is the case even though the cerebellum contains more neurons than the cerebral cortex. Nor do these studies explain how to tell whether consciousness is present, such as in brain-damaged patients, other animals or even computers. Neuroscience needs a theory of consciousness that explains what the phenomenon is and what kinds of entities possess it, Koch said. And currently, only two theories exist that the neuroscience community takes seriously, he said.
Neuroscientist Giulio Tononi of the University of Wisconsin-Madison developed one of the most promising theories for consciousness, known as integrated information theory. Understanding how the material brain produces subjective experiences, such as the color green or the sound of ocean waves, is what Australian philosopher David Chalmers calls the "hard problem" of consciousness. Traditionally, scientists have tried to solve this problem with a bottom-up approach. As Koch put it, "You take a piece of the brain and try to press the juice of consciousness out of [it].
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In contrast, integrated information theory starts with consciousness itself, and tries to work backward to understand the physical processes that give rise to the phenomenon, said Koch, who has worked with Tononi on the theory. The basic idea is that conscious experience represents the integration of a wide variety of information, and that this experience is irreducible. This means that when you open your eyes assuming you have normal vision , you can't simply choose to see everything in black and white, or to see only the left side of your field of view.
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