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The brain learns to see all over again

Can the brain elaborate visual signals even after a prolonged blindness?


A study published in Plos Biology and carried out as a collaboration between the teams of University of Pisa, Foundation Stella Maris and the Neuroscience Institute of the National Council for Research (CNR), coordinated by Maria Concetta Morrone, and the teams of Ophtalmology of Careggi Hospital and of the University of Florence, lead by Stanislao Rizzo, has investigated this aspect by following a group of blind patients with retinitis pigmentosa (RP) that have been implanted a retinal prosthesis ("Visual BOLD Response in Late Blind Subjects
with Argus II Retinal Prosthesis", doi:10.1371/journal.pbio.1002569)

«Scientific literature has shown how even after years of blindness the human brain can "reorganise" itself and the cortical areas once dedicated to elaborate visual signals, and remained thus inactive can take on new functions such as elaboration of tactile or auditory information, comments Elisa Castaldi, first author of the study. Data obtained from this group of patients demonstrate that this process is partly reversible and it is possible to convert those brain areas to perform their original tasks again even though the signal is of a different kind and much distorted».

This study measured the behavioural responses and the brain neural activation with MRI before and after the implant. A neural stimulation system elaborates images from the outside world captured using a camera mounted on the patient's glasses then converts them into electrical signals and transmits them wirelessly to the electrodes implanted in the patient's eye. These electrodes stimulate the axons of retinal ganglion cells. After a learning phase patients come to process visual stimuli. During this time the brain is slowly changing and re-learns to recognise visual stimuli. Results show that after the implant there is growth of brain activity and the increase is greater in patients who train more.

«It's important to keep in mind that these changes happen during several months and there is a correlation between the amount of rehabilitation exercises performed by the patient, the changes in the brain and the ability to use the new instrument. It is as if the brain needs to start learning to see all over again».

«These findings prove that there is great plasticity in the brain not only during childhood but also in adult age, adds Maria Concetta Morrone from the University of Pisa and Guido Cicchini from the Neuroscience Institute of CNR. In addition, we observed that such plasticity is not only limited to the cortex but also to the sub-cortical structures».

«There are more than 40 million blind people in the world and in many cases the cause of blindness is a slow but progressive degeneration of the retina, as in RP, a hereditary pathology, specifies Stanislao Rizzo, lecturer at the Department of Surgery and Translational Medicine. In recent years new hopes were raised for such diseases thanks to the development of new and sophisticated retinal prostheses and photosensitive elements that aim to replace the retina's work and stimulate again the brain with visual signals. To understand the plasticity potential of the brain in the adult is fundamental to improve and optimise future retinal prostheses».

09 November 2016