MSGID: 1:317/3 645091e6   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Scientists discover anatomical changes in the brains of the newly   
   sighted    
    Following cataract removal, some of the brain's visual pathways seem to   
   be more malleable than previously thought.    
      
     Date:   
         May 1, 2023   
     Source:   
         Massachusetts Institute of Technology   
     Summary:   
         Neuroscientists discovered anatomical changes that occur in the   
         white matter of visual-processing areas of the brain, in children   
         who have congenital cataracts surgically removed.   
      
      
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   For many decades, neuroscientists believed there was a "critical period"   
   in which the brain could learn to make sense of visual input, and that   
   this window closed around the age of 6 or 7.   
      
   Recent work from MIT Professor Pawan Sinha has shown that the picture   
   is more nuanced than that. In many studies of children in India who had   
   surgery to remove congenital cataracts beyond the age of 7, he has found   
   that older children can learn visual tasks such as recognizing faces,   
   distinguishing objects from a background, and discerning motion.   
      
   In a new study, Sinha and his colleagues have now discovered anatomical   
   changes that occur in the brains of these patients after their sight is   
   restored. These changes, seen in the structure and organization of the   
   brain's white matter, appear to underlie some of the visual improvements   
   that the researchers also observed in these patients.   
      
   The findings further support the idea that the window of brain plasticity,   
   for at least some visual tasks, extends much further than previously   
   thought.   
      
   "Given the remarkable level of remodeling of brain structure that we are   
   seeing, it reinforces the point that we have been trying to make with our   
   behavioral results, that all children ought to be provided treatment,"   
   says Pawan Sinha, an MIT professor of brain and cognitive sciences and   
   one of the authors of the study.   
      
   Bas Rokers, an associate professor and director of the Neuroimaging Center   
   at New York University Abu Dhabi, is the senior author of the study,   
   which appears this week in the Proceedings of the National Academy of   
   Sciences. The paper's lead authors are Caterina Pedersini, a postdoc   
   at New York University Abu Dhabi; Nathaniel Miller, who is studying   
   medicine at the University of Minnesota Medical School; and Tapan Gandhi,   
   a former postdoc in the Sinha Lab who is now an associate professor at   
   the Indian Institute of Technology. Sharon Gilad-Gutnick, an MIT research   
   scientist, and Vidur Mahajan, director of the Center for Advanced Research   
   on Imaging, Neuroscience, and Genomics, are also authors of the paper.   
      
   White matter plasticity In developed nations such as the United   
   States, infants born with cataracts are treated within a few weeks of   
   birth. However, in developing nations such as India, a higher percentage   
   of these cases go untreated.   
      
   Nearly 20 years ago, Sinha launched an initiative called Project Prakash,   
   with the mission to offer medical treatment to blind and vision-impaired   
   children in India. Each year, the project screens thousands of children,   
   many of whom are provided with glasses or more advanced interventions   
   such as surgical removal of cataracts. Some of these children, with   
   their families' permission, also participate in studies of how the   
   brain's visual system responds after sight is restored.   
      
   In the new study, the researchers wanted to explore whether they could   
   detect any anatomical changes in the brain that might correlate with   
   the behavioral changes that they have previously seen in children who   
   received treatment. They scanned 19 participants, ranging in age from   
   7 to 17 years of age, at several time points after they had surgery to   
   remove congenital cataracts.   
      
   To analyze anatomical changes in the brain, the researchers used a   
   specialized type of magnetic resonance imaging called diffusion tensor   
   imaging. This type of imaging can reveal changes in the organization   
   of the white matter - - bundles of nerve fibers that connect different   
   regions of the brain.   
      
   Diffusion tensor imaging, which tracks the movement of hydrogen nuclei in   
   water molecules, produces two measurements: mean diffusivity, a measure   
   of how freely water molecules can move, and fractional anisotropy, which   
   reveals the extent to which water is forced to move in one direction   
   over another.   
      
   An increase in fractional anisotropy suggests that water molecules are   
   more constrained because nerve fibers in the white matter are oriented   
   in a particular direction.   
      
   "If you see increasing fractional anisotropy and decreasing mean   
   diffusivity, then you can infer that what's happening is that the nerve   
   fibers are growing in volume and they're getting more organized in terms   
   of their alignment," Sinha says. "When we look at the white matter of the   
   brain, then we see precisely these kinds of changes in some of the white   
   matter bundles."  The researchers observed these changes specifically   
   in white matter pathways that are part of the later stages of the visual   
   system, which is believed to be involved in higher-order functions such   
   as face perception. These improvements occurred gradually over several   
   months following the surgery.   
      
   "You see anatomical changes in the white matter, but in separate studies   
   using functional neuroimaging, you also see increasing specialization,   
   as a function of visual experience, similar to what happens in typical   
   development," Gilad- Gutnick says.   
      
   The researchers also tested the participants' performance on a variety   
   of visual tasks and found that their ability to distinguish faces from   
   other objects was correlated with the amount of structural change in   
   the white matter pathways associated with higher-order visual function.   
      
   In comparison, while the treated children showed some improvements in   
   visual acuity -- the ability to clearly see details of objects at a   
   distance -- their acuity never fully recovered, and they showed only   
   minimal changes in the white matter organization of the early visual   
   pathways.   
      
   "The notion that plasticity is a time-limited resource and that past   
   a certain window we can't expect much improvement, that does seem to   
   hold true for low- level visual function like acuity," Sinha says. "But   
   when we talk about a higher-order visual skill, like telling a face   
   from a non-face, there we do see behavioral improvements over time,   
   and we also find there to be a correlation between the improvement that   
   we are seeing behaviorally and the changes that we see anatomically."   
   Benefits of treatment The researchers also found that children who had   
   cataracts removed at a younger age showed greater, and faster, gains in   
   face-perception ability than older children. However, all of the children   
   showed at least some improvement in this skill, along with changes in   
   the structure of the white matter.   
      
   The findings suggest that older children can benefit from this kind of   
   surgery and offers further evidence that it should be offered to them,   
   Sinha says.   
      
   "If the brain has such outstanding abilities to reconfigure itself and   
   even to change its structure, then we really ought to capitalize on that   
   plasticity and provide children with treatment, irrespective of age,"   
   he says.   
      
   Sinha's lab is now analyzing additional imaging data from Project Prakash   
   patients. In one study, the researchers are investigating whether   
   the patients show any changes in the thickness of their gray matter,   
   especially in the brain's sensory processing areas, after treatment. The   
   researchers are also using functional MRI to try to localize visual   
   functions such as face perception, to see if they arise in the same   
   parts of the brain that they do in people born with normal sight.   
      
   The research was funded by the National Eye Institute.   
      
       * RELATED_TOPICS   
             o Mind_&_Brain   
                   # Neuroscience # Intelligence # Brain-Computer_Interfaces   
                   # Child_Development # Perception # Brain_Injury #   
                   Psychology # Child_Psychology   
       * RELATED_TERMS   
             o Occipital_lobe o Brain o Visual_perception o Motion_perception   
             o Neocortex_(brain) o Sensory_system o Retina o Brain_damage   
      
   ==========================================================================   
   Story Source: Materials provided by   
   Massachusetts_Institute_of_Technology. Original written by Anne   
   Trafton. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Caterina A. Pedersini, Nathaniel P. Miller, Tapan K. Gandhi, Sharon   
         Gilad-Gutnick, Vidur Mahajan, Pawan Sinha, Bas Rokers. White   
         matter plasticity following cataract surgery in congenitally   
         blind patients.   
      
         Proceedings of the National Academy of Sciences, 2023; 120 (19)   
         DOI: 10.1073/pnas.2207025120   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230501164006.htm   
      
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