Neuroscientists Identify How the Brain Works to Select What We (Want To) See
ScienceDaily (Feb. 21, 2012) If you are looking for a particular object -- say a yellow pencil -- on a cluttered desk, how does your brain work to visually locate it?
For the first time, a team led by Carnegie Mellon University neuroscientists has identified how different neural regions communicate to determine what to visually pay attention to and what to ignore. This finding is a major discovery for visual cognition and will guide future research into visual and attention deficit disorders.
The study, published in the Journal of Neuroscience, used various brain imaging techniques to show exactly how the visual cortex and parietal cortex send direct information to each other through white matter connections in order to specifically pick out the information that you want to see.
"We have demonstrated that attention is a process in which there is one-to-one mapping between the first place visual information comes from the eyes into the brain and beyond to other parts of the brain," said Adam S. Greenberg, postdoctoral fellow in the Dietrich College of Humanities and Social Sciences' Department of Psychology and lead author of the study.
"With so much information in the visual world, it's dramatic to think that you have an entire system behind knowing what to pay attention to," said Marlene Behrmann, professor of psychology at CMU and an expert in using brain imaging to study the visual perception system. "The mechanisms show that you can actually drive the visual system -- you are guiding your own sensory system in an intelligent and smart fashion that helps facilitate your actions in the world."
For the study, the research team conducted two sets of experiments with five adults. They first used several different functional brain scans to identify regions in the brain responsible for visual processing and attention. One task had the participants look at a dot in the center of the screen while six stimuli danced around the dot. The second task asked the participants to respond to the stimuli one at a time. These scans determined the regions in both the visual and parietal cortices. The researchers could then look for connectivity between these regions.
The second part of the experiment collected anatomical data of the brain's white matter connectivity while the participants had their brains scanned without performing any tasks. Then, the researchers combined the results with those from the functional experiments to show how white matter fibers tracked from the regions determined previously, the visual cortex and the parietal cortex. The results demonstrated that the white matter connections are mapped systematically, meaning that direct connections exist between corresponding visual field locations in visual cortex and parietal cortex.
The researchers used a technique called "diffusion spectrum imaging," a new procedure pioneered at Carnegie Mellon and the University of Pittsburgh to generate the fiber tracts of the white matter connectivity. This method was combined with high-resolution tractography and provides scientists with better estimates of the hard-wired connections between brain regions and increased accuracy over conventional tractography methods, such as those typically used with diffusion tensor imaging.
"The work done in collaboration with the University of Pittsburgh researchers exploits a very new, precise and cutting edge methodology," Behrmann said.
"Because we know that training can alter white matter, it might be possible, through training, that the ability to filter out irrelevant or unwanted information could be improved," Greenberg said.
Additional researchers on this study included Timothy Verstynen, a research associate in the University of Pittsburgh's Learning Research and Development Center, Yu-Chin Chiu, a post-doc in University of California, San Diego's Department of Psychology, Steven Yantis, professor of psychological and brain sciences at the Johns Hopkins University and Walter Schneider, professor of psychology at the University of Pittsburgh. Greenberg, Behrmann, Verstynen and Schneider are also members of the Center for the Neural Basis of Cognition (CNBC), a joint project between Carnegie Mellon and the University of Pittsburgh devoted to investigating neural mechanisms and their impact on human cognitive abilities.
The National Institutes of Health funded this research.
http://www.sciencedaily.com/releases/20 ... 212618.htm
The "gee-whiz" technology is about the only interesting new thing in this study.
Neuroscience has long known about "top down" guidance and filtering in visual perception, and also about "habit bias" fltering in what gets perceived. These researchers don't seem to know about this. They write: "Because we know that training can alter white matter, it might be possible, through training, that the ability to filter out irrelevant or unwanted information could be improved," Greenberg said. Duh? That's the whole point of telling golfers how to perceive slope steepness and green speed and fall line slope direction etc., so they know what difference it makes, and so that they direct attention to what matters with expectations and habits that are veridical.
Jeesh, Carnegie Mellon! Get a book and read it, folks! I've been training these brain processes for over a decade now, and I'm merely a putting instructor who keeps up with the science. If Carnegie Mellon researchers need a bit of top-down help, I'm available.
The other aspect of this research that is interesting (but not new) is the focus on "white matter" which connects cortex "gray matter" from one area to another, here, from the visual cortex to the parietal cortex. The folks at Carnegie Mellon sound like the fact that there is a one-to-one correspondence the way white matter fibers connect one area of cortex to another is a new finding. This is the well-known usual case, folks.
For example, the white matter that connects the back of the eye ball's retinal signals to the Superior colliculus and then onward to the occipital lobe's visual cortex at the back of the head preserves the topographical integrity of the image in the nerve bundles. That's sort of like a fistful of optical cables taking a picture at one end at the retina as light enters and projecting the SAME picture out the other end into the visual cortex. That's well known for decades. Yes, the actual connectivity of the white matter isn't all that well traced out, and this study is helpful, an educated neuroscientist would not find much to get excited about from this study.
Incidentally, the current popular brain book, R. Douglas Fields, The Other Brain: From Dementia to Schizophrenia, How New Discoveries about the Brain Are Revolutionizing Medical Science (New York, Simon and Schuster, 2010), addresses "glia" cells, which in different and in addition to "grey matter" and "white matter". Traditionally viewed as mostly "bubble wrap" packing that supports, separates, and insulates neurons from each other, and also provides the fatty materials that help insulate nerves with myelin that steps up transmission rates, glia cells are classed as "non-neuronal" cells, with no transmission function like gray matter neurons and white matter neurons. but this is now considered incorrect, and glia cells do function in brain cognitive processes. (See, e.g., Swaminathan, Nikhil (Jan-Feb 2011). "Gliathe other brain cells". Discover..
The book The Talent Code is only about the myelination process, and doesn't really express much knowledge about how that process gets accomplished at the physiological-detail level. That's the glia function.
So these folks at carnegie Mellon seem to be playing with a slightly better piece of imaging technology than usual, and their experimental protocol is pretty neat, but the actual conclusions they are drawing from the data are a bit "ho-hum".
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