second from Neue Zürcher Zeitung, 3. 2011
The visual center in the brain of blind people is the Listen or key activated. Now a study confirms that even at higher cognitive as the speech processing is recruited.
By Lena Stallmach
In the brain of blind people remains the central visual system is not wasted. Several areas in the visual cortex in the occipital lobes at the hearing of sounds, read the Braille and enabled the general keys. This raised the question of whether these nerve cells in Braille reading respond to the Tastsensation or the processing of the texts. Marina Bedny from the Massachusetts Institute of Technology (MIT) in Cambridge and her colleagues now show that the visual cortex in the understanding of spoken Language very similar activation pattern as the classical language areas. ¹
with functional magnetic resonance imaging, the researchers measured the blood flow to the brain in sighted and blind from birth subjects. From the measured values, the oxygen consumption and thus derived the activity of nerve cells. The participants listened to the measurement of five different types, but equally long-lasting speech samples from a tape: meaningful sentences, word lists, classically constructed Sets of pseudo-words (nonsense sentences), pseudo-word lists or sentences spoken backwards. A few seconds later a word, pseudo-or backward-word was played, and participants should decide whether this had occurred in the speech sample.
It was found in the classical language areas in the anterior and lateral cortex in blind and sighted people the same pattern: With reasonable rates, the circulation was improved as compared to baseline values much less increase it was with word lists and nonsense sentences. In pseudo-word lists and backward movements she was little changed or lower than at rest.
changes in the visual cortex of sighted subjects, the blood flow compared to baseline values only slightly. In contrast to the blind, they showed a very similar pattern to that of the language areas. She was with reasonable rates much higher than for all other samples, which were sometimes difficult to remember. The visual cortex thus not to speak to the difficulty of a task, but the meaning of the sentence says Bedny, and how the activation with nonsense sentences show on the grammatical structure. Therefore seems the visual cortex in blind people to play a similar role as the language areas in the sighted.
This is an amazing result, says Bedny, as this would mean that the visual cortex processing not only simple sensory stimuli such as pictures, sounds or Tastsensationen, but is also involved with higher intellectual achievements. Fundamental knowledge of this is new, however. In the last ten years, several studies have shown that the visual cortex is activated during language processing in the blind. The neuropsychologist Brigitte Röder, Frank Rösler, who work at the University of Potsdam, Hamburg or used, even a very similar study design and came to the same conclusion. They also asked whether the blind because the recruitment of the additional network benefits in language processing have, and showed that they were quicker at understanding a task few milliseconds as sighted subjects. Rösler criticized the new study appears in a prestigious journal such as "PNAS", although nothing really new shows.
Amedi Amir of the Hebrew University of Jerusalem is not as critical. Although he sees the lack of review of the performance of the subjects had a deficiency in Bednys work. But they do show, however, very convincing as similar to the classical language areas and some parts were working in the visual cortex in blind people.
The observed activity, however, reveals nothing about the function of the visual cortex in language processing. Perhaps it is a by-product and is suppressed in seeing through the visual stimuli. But Amedi showed several years ago that poor blind man in a simple language comprehension test sections, provided that their visual cortex was temporarily paralyzed by magnetic stimulation. The same procedure affected the performance of sighted subjects did not.
Since the visual cortex with the characteristic arrangement of its nerve cells could take on apparently similar functions as the very different design language areas, this means that the condition of the brain regions do not play so great a part, says Bedny. Amedi and thinks that maybe could take every possible function of each brain area . But this must be well proven yet.
¹ PNAS, online publication of 28 February 2011.
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