Naked Science Forum
General Science => Question of the Week => Topic started by: thedoc on 24/01/2011 13:34:06
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How does the brain process Braille? Is it the same as text?
Asked by Frederik Creemers
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We put this question to Dan Goldreich, associate professor in the Department of Psychology, Neuroscience & Behaviour at McMaster University in Ontario, Canada...
Dan: - So, to answer your question, we need to understand how the brain processes both touch and language. With respect to touch, when we move our fingertip over objects such as Braille characters, receptors under the skin produce electrical impulses that race at about 50 meters per second through the nervous system and up towards the brain. This pattern of electrical impulses, a sort of neural Morse code, activates a part of the brain's parietal lobe - roughly halfway between the forehead and the back of the head. This tactile area of the parietal lobe helps to decode the neural impulses, in order to infer the shapes of the objects that touched the skin.
[img float=right]/forum/copies/RTEmagicC_DSC_4050-MR-Braille_1.jpg.jpg[/img]Now, interestingly, in blind people, particularly those blind from birth, touch activates not only this tactile area of the parietal lobe, but also a part of the occipital lobe, in the very back of the head, that is normally reserved for vision. A blind person reading Braille, then, will experience activation of both the tactile area of the brain and the normally visual area of the brain. This unusually extensive brain activation may underlie the heightened sense of touch in blind people.
However, in reading Braille, the brain must not only perceive the shapes of the characters, but once it has done so it must understand those shapes as language. This linguistic understanding is probably not occurring in the brain areas I've just mentioned, but rather in the brain's language areas (such as the area of the temporal lobe - above the ear - called Wernicke's area). So a blind person reading Braille is probably using the same language areas of the brain as a sighted person would while reading print, and as you are right now as you understand the words that I'm speaking.
So, "Does the mind process text in a different way when reading Braille?" the answer to the question is both yes and no.
Blind people reading Braille do show an unusually extensive pattern of brain activation but, once the brain perceives the tactile shapes, the subsequently activated brain language areas used to understand the Braille words are probably the same as those used to understand printed or spoken words.
*Finger size can also affect tactile acuity:
Journal of Neuroscience Dec., 2009: Peters RM, Hackeman E, Goldreich D (2009) Diminutive digits discern delicate details: fingertip size and the sex
difference in tactile spatial acuity. J Neurosci 29: 15756 –15761.
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We had a wonderful answer from a listener:
"Having read print normally until age 17 I had an excellent memory for the
spelling of words and very rarely had to look at a word twice.
"I lost my sight completely and learned braille in a few weeks, although I am
far from a fluent reader. What is interesting is that I am now very poor at
spelling and even though I go over a word many times it simply does not stick
in the memory bank.
"As an extra dimension to your listener's question, I am synaesthetic , such
that words and letters appear in colour, and this was very helpful when it came
to anatomy in my physio course. When, for example, I had to describe
trapezius , I would see this in my head as an orange area on the
shoulder/neck/head and simply describe the picture. I found that even after
forty years of blindness, that this memory is still very strong.
"Therefore, I infer, that my reading of braille is not decoded in the area where
my print memories are stored, but my memory for letter and word colour coding
was unaffected by my sight loss."
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Thank You.
I have studied a second language, and have been aware of subtle differences between the two, especially in retrieval of certain memories. It sounds like learning two different types of reading may be similar.
I hadn't expected an explanation of sensing the Braille in colors. Now, I'm left wondering if the explanation is the same for those individuals who have never seen colors. Or, perhaps it is impossible to actually attribute words to the sensations.