25.03.2016 change 25.03.2016

The human brain is a great reformer

Source: Fotolia Source: Fotolia

The human brain is able to reorganize to a much larger extent than previously thought. If you spend a long time learning a difficult task, its parts "take over" of their respective responsibilities and change roles, just like in people who suddenly lose their sight - showed Polish scientists.

"Biology textbooks teach that the human brain is divided into separate parts. Each of them corresponds to a sense. It is a dogma that the analysis of things that we touch is performed by the somatosensory cortex. When we see something, the analysis is performed by the visual cortex. Auditory cortex is responsible for the listening experience" - explained Dr. Marcin Szwed from the Jagiellonian University.

His team conducted the study, which changes the existing knowledge on the subject. The results show that the brain can change the tasks assigned to particular areas of the cortex, if properly stimulated. "When you devote enough time and energy to learning complicated operations, you can create new brain connections that function over this division" - said Dr. Szwed.

To prove this hypothesis, scientists from Kraków decided to teach 29 sighted volunteers to read Braille blindfolded. "It was the world\'s first group of sighted people who learned to read this way" - noted the scientist.

After more than nine months of study volunteers were able to read 17 words per minute, which roughly corresponds to the reading speed of the blind in the second year of primary school. Before and after the course the functioning of their brains was examined using magnetic resonance imaging. The study showed that as a result of learning, reading with touch activated areas of the visual cortex, not the somatosensory cortex, specifically the Visual Word Centre responsible for the analysis of the written word. The brains of volunteers also developed new connections between the visual and somatosensory cortex.

This is proof - argues Dr. Swede - that in the course of learning this extremely complicated, tactile activity, which is reading Braille, neuronal changes occur not only in the somatosensory part of the cortex, but also its visual part.

In an additional experiment using transcranial magnetic stimulation, researchers briefly inhibited the activity of the visual cortex with magnetic coil. Such temporary shutdown of the visual cortex caused the subjects to suddenly lose the ability to read with touch. According to the researchers, these results confirm that activation of the visual cortex while reading with touch is not a result of visualization of Braille characters in the imagination.

Scientists have long known that the human brain adapts after injuries or loss of vision. "Visual cortex of blind people loses its primary job, but does not remain idle, it switches, for example, to reading with touch and language memory" - said Dr. Szwed. Until now scientists only suspected that such reprogramming is also possible with non-disabled people, but lacked concrete evidence. They only conducted simple studies that investigated somatosensory cortex plasticity, during which subjects trained distinguishing between velvet, velour and corduroy. "For the first time in history we are able to show that the brain of an adult, healthy person can reorganize to such a large extent" - he emphasised.

According to Dr. Szwed, other parts of the brain can also rearrange in a similar manner, not just the visual and somatosensory cortex. "One of the scientists showed his subjects a recording of hitting piano keys, but without sound. While watching this video, in subjects who did not play the piano the visual cortex, or motor cortex activated, because they imagined moving their fingers. But in professional pianists the auditory cortex was also active, despite the fact that they could not hear anything" - Dr. Szwed described in an interview with PAP.

These results demonstrate that we can change the use of parts of our brain when we learn complex tasks, such as playing the piano or driving a car. "If we learn complicated tasks and do it long enough - at least several months - the areas of the brain adapt to new skills and change their roles. This flexibility is due to the fact that our brain is able to overcome its default division of responsibilities and create new connections that enhance its capabilities. The brain of an adult is much more flexible than previously thought" - described the scientist.

Another group that learns to read by touch has been formed in Warsaw. "Now we will focus on the connections that form during the learning process in the nerve fibres of the brain and how the thickness of grey matter increases" - the researcher announced.

The study - published recently in the journal eLife - was funded by the National Science Centre. The article is available at: http://dx.doi.org/10.7554/eLife.10762

PAP - Science and Scholarship in Poland, Ewelina Krajczyńska

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