Synaptic Pruning

Back again :) Today's post is on synaptic pruning, read on and you'll see it's quite similar to neuroplasticity.




What Is Synaptic Pruning?


When you’re young, your brain is hyper-connected. However, as you get older some of those extra connections- synapses- are eliminated through a process known as synaptic pruning that occurs between early childhood and adulthood.


To review, synapses are neural structures that allow for electrical/chemical transmission between neurons.


We know that through neuroplasticity, connections within our brain are strengthened and new connections are created, as neuroplasticity is the forging of new neural connections. Synapses work in a similar way. Once a synapse is formed, depending on how often it is used, it gets either stronger or weaker. Actively used synapses are strengthened, while those that are not, get weakened. The barely used or "useless" synapses are the ones that are eliminated during the process of synaptic pruning. In order for a synapse to be kept permanently, it requires consecutive activation and use.



Why Is Synaptic Pruning Important?


The process of synaptic pruning is key to brain maturation and is thought to create a "more efficient brain", as with eliminated extra synapses and neurons, comes better neuronal transmission. As we age and learn more complex information, the eliminated connections provide for heightened brain function and better neural ability. Think of it almost like a clean-out for your brain- you keep what you use.


Timeline of Synaptic Pruning


It's important to note that the timing of synaptic pruning does vary by brain region. The prefrontal cortex sees the most abundant amount of synapses during the first year of life. The visual cortex sees this when you're around 7-8 months old, however, the pruning continues up until around age 6.


Infancy


During infancy, there is a drastic amount of growth in your brain. Your brain actually overproduces neurons and synapses, which is why synaptic pruning is so essential for healthy brain function as it keeps the numbers in check. In fact, a process in which an abundance of synapses is formed between neurons occurs- synaptogenesis. Synaptogenesis is extremely important for neural development, specifically cognitive functions such as memory and learning.


Early Stages of Life


At the early stages of life, your brain has ample synapses but a few years down the road, it starts to get rid of the synapses it no longer requires. Synaptic pruning in the early stages is often affected by genetics. Here, the total amount of synapses in your brain goes down drastically as most of the pruning happened in the years prior. Almost 50% of the 'extra' synapses are removed. Most of the change happens during the years 2-16.


Adolescence


Although not as much as before, synaptic pruning still happens during adolescence. The total number of synapses now begins to establish. Back when there was a proliferate amount of synapses and connections during infancy and early childhood, it was difficult for your brain to differentiate between which synapses needed to be kept. As with age comes experience, which now allows for the elimination of certain 'useless' synapses based on the frequency of their usage- thus why there is a period of pruning during late adolescence.


Adulthood


Synaptic pruning continues into the early stages of adulthood and stops sometimes in your 20's. There isn't nearly as much pruning that occurs in these stages as compared to childhood, but it's still there. Recent research has disproven the idea that synaptic pruning ends during childhood/early adolescence and instead, the process has seemed to continue well into adulthood.


Synaptic Pruning & Neurodegeneration


Neurodegenerative disorders such as schizophrenia, which is often diagnosed in early adulthood, have been recently thought to be relative to synaptic pruning. If the process doesn't happen correctly, there may be more room for neurodegeneration and similar issues to arise. It also may be thought that if there are too many connections in the brain, it could possibly limit learning and other neural capabilities. Further research is yet to be conducted linking the relations between synaptic pruning and neurodegenerative disorders.










Thanks for reading :)

Sources:


https://www.pnas.org/content/117/28/16096


https://www.healthline.com/health/synaptic-pruning