Eyeworld

EW NEWS & OPINION 20 October 2017 by Liz Hillman EyeWorld Staff Writer they make decisions about what to do—are we going to open the channel and what kind of molecular pathways are going to be triggered? Is this going to strengthen or weak- en the synapse? It's the ongoing dynamics as well as the longer-scale, lifetime changes. That's why I target- ed looking at the synaptic proteins. I see them as a key piece in the puzzle that can bridge the gap between structure (anatomy, neuroanatomy) and function (behavior and neuro- physiology)," she said. One of the synaptic mech- anisms studied was the NMDA receptor, which Dr. Murphy said is important for neuroplasticity. This receptor is made up of different pro- tein subunits. Two of them, which for simplicity's sake, Dr. Murphy described as A and B, are critical for plasticity. In their analysis, the research- ers found the ratio of A and B starts with more B early in development and shifts to more A. "One of the key findings in our paper is that shift from more B to more A continues until the mid-30s," she said. "The key thing about that balance between A and B has been very hotly studied in the animal models, and a lot of different potential treatments have been in- vestigated that manipulate that bal- ance. We know quite a bit from our animal models about what could be a good balance for promoting plas- ticity. The interesting thing from our study is that potential balance is still present in human visual cortex into the teen years. The training kinds of treatments for visual disorders could still be tapping into neuroplasticity mechanisms for quite a bit longer than was thought before." Dr. Murphy also noted that the balance of A-B starts to shift back to more B after the mid-30s, suggesting another period of plasticity in the 50s and 60s that she said could be tapped into for potential treatments. Ultimately, the researchers broke down development over the lifespan into five stages. Dr. Murphy described them in computer terms. The first stage—the first year—is booting up the system, getting the computer turned on, and making sure the operating system is loaded, she said. Next, 1–5 years old is when we're uploading our software, mak- ing sure all the programs we need ple, ranging in age from 20 days to 80 years old. The goal was to study the development of these proteins (glutamatergic proteins specifically) to potentially explain this discrepan- cy between the structure of the pri- mary visual cortex and its function. Picture a Venn diagram where one circle is structure (the anatomy) and the other is function (visual perception, neurophysiology), Dr. Murphy said. In the middle where there is overlap are proteins at the synapses. "The way I like to think about these proteins is they're the archi- tects of function. They sit there at the synapse … they make all kinds of decisions, what transmitters are going to be released on the post-syn- aptic side, where the receptors are; "Ophthalmologists and optom- etrists get very focused on vision at the level of the eye, and they often forget that the engine that allows us to see is the brain," Dr. Murphy said later, explaining that her team's findings ultimately could impact current treatment of certain ocular disorders, such as amblyopia, thera- pies currently in animal models, and other areas of brain research. While the anatomy of the hu- man primary visual cortex appears to mature early, vision changes over the person's lifespan, Siu et al. explained in the study published in the Journal of Neuroscience. The researchers described how they analyzed proteins from the primary visual cortex (V1) in post-mortem brain tissue from 30 different peo- This could mean certain treatments thought only efficacious in childhood could extend into teen years or young adulthood N ew research bucks the commonly held thought that the human prima- ry visual cortex reaches maturity in childhood with findings that show it reaches maturity in the mid-30s. "That's at least 25 years longer than anyone had predicted before these findings," said Kathryn Mur- phy, PhD, professor and director, neuroscience graduate program, Mc- Master University, Ontario, Canada. Research finds human visual cortex continues development into mid-30s Research highlight

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