A Headful of Words

Article excerpt

Our heads are stuffed full of words and yet somehow our brains manage to make sensible use of them. It's a curious situation that the poet T. S. Eliot describes as "the intolerable wrestle with words and meanings." Amazingly, up until fairly recently, we had only very rough ideas as to how our brains process language. However, developments in neuroscience investigations mean that researchers are starting to gain a much more legible picture of what happens in our heads when we speak, listen, and read. Researchers are currently using the fascinating technique of "brain imaging" to investigate various aspects of how our brains handle language, including how we deal with our own language and foreign languages, and how dyslexics handle words.

Just ten or fifteen years ago, most scientific knowledge of how our heads processed language stemmed from research on patients with brain damage. Scientists studied people who had suffered strokes or other forms of brain impairment, and they gained a reasonable idea of which areas of the brain controlled which functions.

For quite some time it has been known that the left-hand side of the brain is generally more involved in language functions. This is tree for 97-98% of all right-handed people (who make up around 90% of the population). Most left-handers (around 67-68%) also use the left hemisphere for language functions, though left-handers in general tend to make more use of both hemispheres when dealing with language. Left-handers are generally good at art and music, and at recognising faces, but in many cases they have greater difficulties with language, and dyslexia appears to be more common among left-handers.

It takes very little to show that for most right-handed people, it is the left-hand side of the brain that is at work when language is being processed. Try this little experiment. Read a paragraph or so of this article 'aloud and at the same time, tap a finger of your right hand in a fairly regular rhythm. Then do the same tiring while tapping a finger of your left hand. You probably noticed that you had a harder time tapping with your right finger because it is your left-hand side of the brain that is doing 'all the work (processing the language and controlling the movements in your right hand).

For the vast majority of people, therefore, the left hemisphere of the brain controls language functions, and certain specific areas within the left hemisphere can be singled out as "language centres." Decades of observing brain-damaged patients allowed researchers to piece together a fairly good picture of what goes on in our heads when we use language. Many of these language areas are located deep inside the brain, far from the cortex, especially around what is known as the Sylvian fissure--a deep pleat in the brain that runs more or less parallel to the line from the eye to the ear. Close to the Sylvian fissure lies Broca's area, which is mainly involved in controlling the mechanical aspects of speech. Another nearby sector, the temporal lobe, looks after hearing perception. Within this latter part of the brain, Wernicke's area is believed to be responsible for finding words and feeding them to other parts of the brain. Next-door, the angular gyrus (a gyrus is a "ridge" in the brain) helps to make sense of the words and letters we come across when reading.

Only fairly recently have researchers been able to gain a clearer picture of what happens inside the brain, thanks to techniques known as brain imaging or neuro-imaging, which make use of machines originally developed for medical purposes, such as the widely known CT scanner. Much more effective for linguistic purposes, however, is the PET scanner, providing positron emission tomography scans. A PET scanner detects a radioactive substance that has been injected into or inhaled by a subject or patient. When in the bloodstream, the substance tends to gather in the most active areas of the brain, and PET scans therefore indicate the areas that are at work during any particular mental task. …