The electrodes in the head

Diameter of coin is 25 cents, which has a grid of 16 microelectrodes, is 24.26 mm. On the coin shows the attraction of Utah - it is here that created these electrodes, and found it unusual use (photo Spencer Kellis, The University of Utah).




Scientists from the University of Utah (U of U) and Washington (UW) to destroy the dream of a wall surrounding the patient with ' locked man syndrome ' (locked-in syndrome). Due to a number of ways of neural damage such a patient can not talk or move, although fully aware of everything and is able to blink.

Often, only the movement of the eyes and allows you to make miserable the questions most simple answer - yes or no. In the new work, researchers have expanded this primitive vocabulary to 10 words. In addition to the above is ' hot ', ' cold ', ' hungry ', ' desire ', ' Hello ', ' Goodbye ', ' more' and ' lower '.


As Americans used the experimental volunteer, who had already been made a temporary craniotomy. This patient suffers from a severe form of epilepsy. By placing electrodes on the cortex of the brain, doctors hope to establish one point of causing seizures. Subsequent surgery may solve the problem.


In the meantime, the skull remained opened, the experimenters took the opportunity to explore other areas. Experts agreed that the recording pattern of neuronal activity would tell them - in the brain where specific words are born.






Here you can see two types of electrodes on the surface of the patient's brain. Major - the ones that doctors use to identify the source of epileptic seizures. But the green and orange wires terminate the experimental arrays of 16 microelectrodes. Recent marked with white dots, as in the original shot poorly visible (photo by University of Utah Department of Neurosurgery).


It has already been shown that by using an electroencephalogram, removable ' brain cap ', can be successfully managed with a board game, connect the brain with the brain, play in the orchestra and the commanding android. But in those cases, the device is placed outside the human. Physical penetration of a skull can give researchers more information.


It is important that the team used its expertise previously developed at the University of Utah's ' gentle ' an array of microelectrodes (microECoG) for elektrokortikografii (they are shown in the picture above). These devices do not penetrate into the brain, and lie on the surface and feel the potential of the field formed by neurons.


And the new electrodes are much smaller than previously used, and are separated from each other at a distance of only one millimeter, which allows you to record the signals with a high selectivity.


The researchers placed two arrays of microelectrodes for 16 (squares 4 x 4) in two zones of the brain. First - facial motor cortex that controls movements of the mouth, lips, tongue, in general - the muscles involved in speech. Second - Wernicke area associated with perception and recognition of words ( she works in the utterance of the man himself ).


For four consecutive days with the patients underwent an hour of training. The patient spoke at the bidding of scientists is one of the ten words, each 31 to 96 times. After examining a set of pulses, the authors of the experiment set up for each word the most representative figure of active electrodes. And to check speculation, Americans spent a few tests on guessing words.






This tomographic image, scientists have imposed the attachment of electrodes. Yellow - old and needed to find the source of attacks, red - two sets of microECoG, are in the areas of speech (photo by Kai Miller / University of Washington).


Reading from an array of motor cortex, in accordance with the previously unidentified sets of ' individual ' for each word of the electrodes allowed the right to define these very words in 85 % of cases. Work only with Wernicke's area gave only 76 % accuracy.


Interestingly, the combination of signals from the two regions on the quality of the definitions are not affected. Consequently, the Wernicke area here is of little. By the way, when the subject uttered the words, his motor cortex was more active than Wernicke's area, and when I heard - the latter sharply connected.


This principle - ' spy, remember to compare ' - previously used for such experiments as the removal of the heads of the subjects and the number of photos, texts seen, heard the words, the spatial position and style of the artist.


And it is not so important what kind of technology is used Read innovators - magnetic resonance imaging or shooting electrocorticogram. The main thing - to identify the activity of certain groups of neurons in different regions of the cortex with the desired accuracy.


Because then our heroes are calculated in each of the two arrays microECoG five contacts, changes in the signals which were most striking when you change the words. Relying only on them, scientists were able to increase the accuracy of registration of pre- selected word up to 90%. (Details of the experiment reveals a press release the University of Utah and an article in the Journal of Neural Engineering. ).


To implement the idea of ​​mental impulses of speech is necessary to record from all electrodes at once and identify specific images of neuronal activity patterns superimposed on each other. After tasting it, the inventors of technology were accurate 28% to record from all electrodes ' wholesale ' and 48 % for detecting signals only from the ' best ' five electrodes microECoG.


These numbers are clearly above the ten percent hit, which follow from the theory of probability, if the recognition of words was purely accidental. But at this level, of course, is not enough to organize a full reading speech.




Last year, Greger and his colleagues at the University of Utah professor of neurosurgery in particular, Paul House (Paul House), shown here in the operating room, had a successful experience of reading with microelectrodes motor brain signals that control the patient's hand. House took part in this experiment (photo Kelly Johnson).



Bradley Greger (Bradley Greger) from the University of Utah, an expert on Bioengineering and one of the authors of the present experiment, said: ... But we have to handle more words with greater accuracy before it will be useful for the patient '.


The invention microECoG just gives hope for a breakthrough. The electrodes used by researchers and clinicians in the previous works have been inconvenient for experiments on mental speech. They immediately took over too many neurons to extract from their readings so subtle differences that accompany the formation of speech. So, you need to go further along the path of increasing detail.


By the way, another research group in the past year, using a similar method was able to isolate from the head of the paralyzed vowels. Against this background of 10 words may seem a revolution, but the ' revolutionaries ' perceive their success restraint.


' That does not mean that the problem is completely solved and we can go home - continues Greger. - Verify that the technology, now we need to optimize it so that patients with the syndrome of trapped people could really talk '.


In the words of Bradley, the next step the group - to build an array with 121 microECoG electrode (11 x 11). They will help you get a huge amount of information that is likely to mean more recognizable words.


Over time, this technique can be embodied in a wireless chip implant ( similar to the prototype ), which transmits radio signals to the computer activity of neurons in order to reproduce the above PC in my thoughts. The first is a serial system will be a truly revolutionary.



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