How is a river like a neuron?
Scientists are always finding that things we thought would never change are actually in constant motion. Up until just a century ago, it was thought that the earth itself was unchanging. The connectome is no different. Neuroscientists have found that the connections between your neurons will change over time.
In the same way that someone can tell where the riverbed is just by looking at the river, neuroscientists can tell where there are connections based on how neurons fire together. One of the unseen processes of the river is how it changes the riverbed; over time, the flow of water will change the shape of the riverbed, which will eventually change the path of the river. Just as the river shapes the riverbed which guides it, neural activity shapes the connectivity in the brain, redefining your connectome.
The Four ‘R’s of your changing connectome
A synapse’s size is an indicator of it’s strength. Synapses grow and shrink based on use; the more often a synapse is used, the larger it will become. Alternatively, if a synapse is unused for a long enough period of time, it may shrink and eventually disappear. The process of synapse growth and shrinkage is known as reweighting.
Neuroscientists attempt to model synapse reweighting using Hebb’s Rule. This rule describes how the firing of one cell will affect another one over time. Neuroscientists attempt to model synapse reweighting using Hebb’s Rule. By improving on this rule, the models of synapses will be a better representation of real synapses.
Rather than creating synapses at the specific locations that they are needed, neurons create synapses seemingly at random. As synapses get reweighted, synapses that shrink will be eliminated, while the others will be kept. This process, called neural darwinism, is thought to be responsible for transferring memories from short term to long term.
One of the leading theories in neuroscience is that the brain’s functionality is made possible by coordinated functional, genetic and connectomic relations between regions in the brain. To find the connections, neuroscientists map axons in the brain. Because the wiring of the brain plays an important role in defining it’s function, it is thought that in order to retain function in a damaged brain, the neurons will rewire.
The olfactory bulb and the hippocampus are the only two regions in the brain to create new neurons. It is unclear as to why neurons are only created in these two regions, but there are some theories that the stability of the brain is required for the continuing storage of old information. Scientists hope to replicate the process of neuron regeneration for other parts of the brain to help treat brain damage.
Learn more about the science of connectomics at http://blog.eyewire.org/behind-the-science-an-introduction-to-connectomics/