Researchers show there's more than one way to read - with implications for reading disorders

By Max McClure
Andreas Rauschecker with the transcranial magnetic stimulation apparatus. The model's headgear is used to precisely target the procedure's disruptive currents. Credit: L.A. Cicero

(Medical Xpress) -- With specificity and precision, the brain's Visual Word Form Area, or VWFA, does exactly what its name implies. Every time we see something that looks like a word, it activates. The VWFA is so adept at packaging visual input for the brain's language centers that the task of word-recognition only takes a few tens of milliseconds.

Still, the problem of picking out words from a visual scene is strikingly complex –complex enough that it is currently used to distinguish human Internet users from automated software programs. If you've ever been asked to type out a distorted word before gaining access to your email – a security test known as a CAPTCHA - you've proven that you're a better reader than your computer.

In a research paper appearing in last week's Neuron, neuroscientists from the Stanford Vision Imaging Science and Technology Lab demonstrate that one key to VWFA function is its ability to recognize words through more than one visual pathway.  The finding not only demonstrates the flexibility of the human visual system, but may also have implications for our understanding of dyslexia and other reading disorders.

When the VWFA was first identified in 2000, the very existence of a region devoted specifically to was considered surprising. Reading is an activity that has only become widespread in recent human history.

"It didn't originally evolve for reading," explained Andreas Rauschecker, the primary author of the Neuron paper and an MD/PhD candidate in Stanford's Medical Scientist Training Program. "We likely invented reading to give the VWFA what it likes to see."

Located in the ventral occipitotemporal cortex at the back of the brain, the VWFA appears to act as a relay station between the primary visual cortex and the brain regions dedicated to language recognition and production. As an individual's reading ability improves, her VWFA has been shown to expand into neighboring brain regions, including the region devoted to facial recognition.

But what does the VWFA find "appealing" about words? Traditionally, researchers have thought of words as defined by "luminance contrast" – black letters on white paper, for instance. Rauschecker, however, was interested in a potential alternate pathway.

Instead of being "luminance-defined," words can be "motion-defined" – distinguishable from their background not by color or contrast, but by their apparent direction of movement. Against a field of dots moving one way, words made up of dots moving in the other direction will "pop out" to most viewers, even if the word and background dots are the same shade.

"In some ways, this is an especially extreme version of a CAPTCHA," said Rauschecker.

Participants in the study were asked to read while their brains were scanned by a functional MRI (fMRI) machine. The researchers presented the participants with various types of words – defined by either motion or luminance contrast – and watched for activation of the VWFA (Video example of the motion-defined words viewed by study participants.)

The researchers reasoned that, if the VWFA were only looking for a basic visual feature, such as the shapes of black-on-white letters, it shouldn't activate in the presence of motion-defined words. But scans showed that the VWFA responded equally to all legible words.

The result implied that the VWFA can receive information from the human MT complex, or hMT+: a region of the visual cortex necessary for motion perception.

The fMRI scans showed that the hMT+ did activate in the presence of motion-defined words, although it was unresponsive to other types of words. This finding suggested the existence of two separate visual pathways to the VWFA.

The researchers also precisely targeted transcranial magnetic stimulation to each individual's hMT+. The technique, which applies a rapidly changing magnetic field to induce an electric current in the brain, can be used to briefly inject noise into specific brain regions, temporarily disrupting function. Stimulation dramatically reduced reading performance of motion-defined words while leaving luminance contrast-defined words unaffected.

"How exactly the information ends up in the VWFA depends on the specific visual features," Rauschecker said. "There's very flexible routing."

And the pathways seem to be partially additive. A word that is defined by both motion and color inspires a stronger VWFA response than a word defined by one or the other.

This feature offers the possibility of compensating for specific reading disabilities by designing electronic typefaces that could re-route visual information through undamaged areas of the brain. A digital font with a movement component could potentially increase legibility for some of those who have difficult reading.

The participation of hMT+ in the pathway is particularly interesting, as previous studies have shown that the region is less responsive to motion in dyslexics.

"That was something of a random finding," said Rauschecker. "There was no reason to think that, by showing people a moving stimulus, you should be able to predict their reading ability."

The research raises as many questions as it answers. Motion-defined words are an unusual stimulus, and the role of hMT+ in normal reading is still unclear. It may be involved in a reader's ability to switch rapidly from one word to the next in a sentence, though this remains only a theory.

Even the VWFA itself isn't the end of the word-recognition story. Participants also performed a decision task during their fMRIs, identifying words as either real words or nonsense words. VWFA activation was necessary for correct identification – but not sufficient.

The paper's senior author was Brian Wandell, a professor of psychology at Stanford. Funding for the research was provided by the Bio-X Graduate Student Fellowship to Rauschecker and a National Institutes of Health grant to Wandell.

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Jeffhans1
not rated yet Sep 15, 2011
When hunting in groups a form of sign language is often used to this day. Staying silent and undetected would be a huge advantage for people who are limited to muscle strength for propelling spears, rocks or arrows. I would like to see if this same region of the brain is used for people who communicate by sign language.
tgoldman
not rated yet Sep 15, 2011
this connects with observation that crawling (infants) is an essential element in developing reading ability -- moving dots may be what the VWFA evolved for in the first place. recall article regarding treatment of reading disorders/disability by having even adults spend time crawling
DarkHorse66
not rated yet Sep 16, 2011
The definition of this motion can defined in two distinct ways.
1. The text is moving while you hold your eyes still.
2. The text is stationary, while you are moving your eyes along the sequence of words in the line. Both have the same effect as the end product. It doesn't matter if the text is moving relative to the eyes, or the eyes are moving relative to the text. In both cases we have motion. In fact if you think about it, motion is INTEGRAL to being able to read sequential words. This goes for reading a vertically constructed list too.

Cheers, DH66
DarkHorse66
not rated yet Sep 16, 2011
P.S.
I'm just a little disappointed that they are so surprised about the presence of a separate motion activated pathway. It didn't seem to occur to them that a full word might be picked up and interpreted by the brain by using a single stationary glance, BUT this 'shortcut techique' tends to fail when you have to take in an entire sentence. Even then, you might still be 'seeing' entire words, but you then have to 'word hop' in order to take it all in. (Try it out, you'll see what I mean)Guess what fella's: motion. Without it, we wouldn't able to read very far at all... Single word post-it notes anyone?
hush1
5 / 5 (1) Sep 18, 2011
Wait! There's more!...

http://www.google...;cad=rja

Synesthesia.
No. Not the Sound of Music.
The sound of motion. :)
hush1
5 / 5 (1) Sep 18, 2011
These unusual physiological phenomena are sources of invaluable information. "Wrong" turns of information carriers (neuronal signal pathways) ending up at locations where the only interpretation allowed for these signals is a landscape foreign to the incoming information:
This reveals what "motion" is for a brain region handling this information in the only fashion the associated pathways allow: From the perspective of sound only.

Whether this "fashion" is unique only to an individual or a universal default mode handling for everyone for identical motion expressed by sound landscape remains to be discovered.
DarkHorse66
5 / 5 (1) Sep 19, 2011
It's more fun experiencing colours and watching their beautiful movements (a symphony of colours is the best way I can describe it. No two occasions are quite the same, even when triggered by the same sound.) when they are being triggered by sounds, rather than the other way round. But then again, I am a more visually oriented person. I should point out that taste and smell (despite the fact that they are considered separate) are only at their best when they work together, especially when it comes to the full experience of 'tasting' the full nuances of food. If you don't believe me, try evaluating flavour when you have a nasty cold, or hold your nose shut while eating. Having said that, synesthesia is just cross-wiring of particular senses and can occur in any combination(s).
Cheers, DH66
DarkHorse66
not rated yet Sep 20, 2011
For anybody who is curious: Another variation of the above colour-theme is 'seeing' coloured letters, entire words and numbers. Also shapes can differ. For example, if I picture the number '2' in my head, it takes on a mustardly-yellow appearance. Its appearance is 'not too fat, not too thin'. If however, I picture the number '20', there is a superimposition of a cream-like white and opaque black. (As strange as it may be, one does 'see' both colours in the same place, yet can distinguish between them completely.) Unlike the single '2', the number itself looks very slender. My own alias is red. I should point out that this kind of 'system' is not contrived, it's just there. Even a change in mood can vary the outcome.
Cheers, DH66
DarkHorse66
not rated yet Sep 20, 2011
For those who are having trouble 'picturing' the effects of synesthia, here is a quick description of what can be perceived visually, when hearing a sound (bearing in mind that everybody who has this, will experience their own variation):

Ding-Donnnggg! (Doorbell)
A scintillating mosaic of multicoloured points rising and falling. Rising and falling in a grand quick sweep, that much resembles a very large shoal of very small fish, all darting with the current. Rising and falling, in complete harmony with that short and not unpleasant sound. Then falling away. To nothingness.
Cheers, DH66
hush1
5 / 5 (1) Sep 20, 2011
"Cross-wiring" is a harsh mistress*. The mistress* I have in mind is a mistress* that provides "rewiring" for the sake of well being, compensation for loss and continuation of self survival:

If motion (normally handled as a visual signal) harbors a dual potential to provide or act additionally as a signal (either provisionally or permanently) for sound as well, then ANY PHYSICAL shortcoming or malfunctioning of a hearing process can be reliable compensated for IF THERE EXISTS a dual (or more) signal potentiality for ALL signals - not just signals of motion.

Sound of motion is irrefutable evident of signals that ALWAYS have more than one "physical" 'meaning' - brains's interpretation variability for the sake of survival. Never let any signal go to waste. She's** is not a fool - there is nothing closer to the sensation of sound than motion.

This multi-signal potentiality hypothesis applies to ALL sensory signals for ALL physically perceptible sensations.

*/**Nature