Selective neural connections can be reestablished in retina after injury, study finds

Physical and Biological Sciences News

A cross-section of healthy retina shows S-cone bipolar cells (marked by *) in the inner nuclear area. Each bipolar cell sends a single dendrite toward the photoreceptor ribbons (magenta) to synapse with a single S-cone photoreceptor (blue). (Image credit: Beier et al, 2018, Current Biology).Bipolar cells left without a connection to a photoreceptor start to grow new branches, called dendrites. This image shows two S-cone bipolar cells (marked by *) contacting the same S-cone axon terminal (arrowhead). The dendrite from a deafferented S-cone bipolar cell bypasses M-cones to synapse with new S-cones. (Image credit: Beier et al, 2018, Current Biology).The brain’s ability to form new neural connections, called neuroplasticity, is crucial to recovery from some types of brain injury, but this process is hard to study and remains poorly understood. A new study of neural circuit repair in the retina shows that neurons can make new connections to the right types of photoreceptors to restore selective connectivity after an injury.
“It is essential to understand these processes because we don’t get new neurons in the central nervous system, and even if we learn how to introduce new neurons, we still need them to integrate in the correct way. Here we show there is a mechanism in adult mammals to ensure the correct connections are made,” said Alexander Sher, associate professor of physics at UC Santa Cruz and corresponding author of the new study, published May 24 in Current Biology.
Vision loss from diseases such as age-related macular degeneration and retinitis pigmentosa results from degeneration of the light-sensing photoreceptors in the retina. Medical researchers have begun to explore potential therapeutic strategies to replace the lost photoreceptors. This approach could only work, however, if the new photoreceptors could be connected properly to the neural circuitry in the retina.
“Our findings provide some hope that if new photoreceptors can be introduced and survive, the correct connections …

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