Image: Dan Winters
In Brief
- The cerebral cortex is the structure that gives the organ its convoluted surface. It is involved with high-level processing of our perceptions, thoughts, emotions and actions.
- Intricate folding permits the expansive cortex to fit inside a skull with limited surface area.
- Recent discoveries have shown that mechanical tension between neurons creates the hills and valleys of the cortex.
- The cortical landscape differs between healthy people and individuals with brain disorders that originate during development, such as autism. These shape differences suggest that connections between brain regions of affected individuals also depart from the norm.
One of the first things people notice about the human brain is its intricate landscape of hills and valleys. These convolutions derive from the cerebral cortex, a two- to four-millimeter-thick mantle of gelatinous tissue packed with neurons sometimes called gray matter that mediates our perceptions, thoughts, emotions and actions. Other large-brained mammals such as whales, dogs and our great ape cousins have a corrugated cortex, too each with its own characteristic pattern of convolutions. But small-brained mammals and other vertebrates have relatively smooth brains. The cortex of large-brained mammals expanded considerably over the course of evolution much more so than the skull. Indeed, the surface area of a flattened human cortex equivalent to that of an extra-large pizza is three times larger than the inner surface of the braincase. Thus, the only way the cortex of humans and other brainy species can fit into the skull is by folding.
This folding is not random, as in a crumpled piece of paper. Rather it exhibits a pattern that is consistent from person to person. How does this folding occur in the first place? And what, if anything, can the resulting topography reveal about brain function? New research indicates that a network of nerve fibers physically pulls the pliable cortex into shape during development and holds it in place throughout life. Disturbances to this network during development or later, as a result of a stroke or injury, can have far-reaching consequences for brain shape and neural communication. These discoveries could therefore lead to new strategies for diagnosing and treating patients with certain mental disorders.
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12 Comments
Add CommentNASA seems to be spending a lot of words Hyping the connection of methane producing microbes on Mars .. rather than giving equal attention to methane producing geological/chemical processes. It would have been more scientific to say that, "An increase in methane into the atmosphere has been detected but the cause is not known." tomb
Reply | Report Abuse | Link to thisIf autistic people have more connections among neighboring brain areas but fewer connections between distant brain areas, could science discover some way to give all people (autistic and otherwise) abundant connections among neighboring *and* distant brain areas?
Reply | Report Abuse | Link to this@Kate - more connections do not imply better functioning
Reply | Report Abuse | Link to this@article authors - big AUTISM in title, weak links in text
the specific pattern of brain folding certainly couldn't have been designed and engineered that way, could it?
Reply | Report Abuse | Link to thisSince there's no factory designing and/or engineering brains, I'd have to say...no.
Reply | Report Abuse | Link to thisBut, I'm sure that wasn't your intent. Your intent was to try and get people to think "hey, this is some complex stuff, it couldn't have possibly happened without the intervention of the Supreme Fairy", right? You people are so sad. Why do you always have to take something that's so spectacular, so glorious as the construction of the brain (or organism or galaxy or planet or universe) and reduce it to "the Fairy said it should be, and it was"?
The stuff these people write with a straight face.
Reply | Report Abuse | Link to thisBrains grew bigger, so they had to fold to fit. But the folding isn't random, it's patterned. And the folding uses a complex mechanism. And it all just happened in perfect synchronization.
So, tell me, SA. Where are the huge amounts of deformed skulls that would HAVE to result by the selection not getting it quite right the first million or so tries.
Maybe because he recognizes delusion when he sees it. The very idea that all this could happen in perfect synchronization (proven by the lack of fossils showing deformities that would result from failures to get the folding right) is the height of self-delusion at work.
Reply | Report Abuse | Link to thisApparently, critical thinking is not a requirement in evolutionary thought.
The earth is 12,000 years old, the first woman made by a sky daddy from a mans rib and snakes talk, when i don't knows something or see something thats amazing I just say god did it. I'm a critical thinker. My sky daddy is building me a big house in outer space i get to go to after i die.
Reply | Report Abuse | Link to thisIf you read the article then you know that even small mammals have some folding.So from an evolutionary perspective by the time it got to us or even ausrtolopithicus it had gotten it right.These abberations would probably have occured in rat sized or smaller mammals, before we were even walking the earth. My guess is folding started with sea mammals, but its just a guess!
Reply | Report Abuse | Link to thisAs an 60+year old somewhat autistic, very dyslexic person I have been called lazy. willful and stupid, but never diseased. I like the way my brain works. Whether abi-normal or subi-normal it suits me. Sometimes there are benefits to having a different point of view.
Reply | Report Abuse | Link to this"By the time of birth the cortex has more or less completed development and attained its characteristically wrinkled form." This contradicts the idea that vaccines cause autism.
Reply | Report Abuse | Link to thisThe axon tension-based theory is just speculation. I'm surprised that for so many years there is no direct test on this. A recent study published in Journal of Biomechanical Engineering,"Axons pull on the brain, but tension does not drive cortical folding", provides some striking experimental evidence that the distributions and patterns of tensions and axons during ferret brain folding are not consistent with a causal role. Instead, folding could be driven by coordinated differential growth. A tension speculation may sound nice enough to believe, but it is wrong.
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