Neuroplasticity
UC Davis neuron image
Main Takeaways. Questions, Moments of Genius…
Broadly speaking, there are now two main types of neuroplasticity. Functional plasticity involves changes in some physiological aspect of nerve cell function, such as the frequency of nervous impulses or the probability of release of a chemical signal-both of which act to make synaptic connections stronger or weaker-or changes to the degree of synchronicity among populations of cells. Structural plasticity includes volumetric changes in discrete brain regions and the formation of new neural pathways, brought about either by the formation of new nerve fiber branches and synapses or by the growth and the addition of new cells.
Blind people can also learn to navigate by echolocation [either with clicking with their tongue, or tapping their feet] and using the information in the returning echoes to perceive physical aspects of their surroundings. This requires huge amounts of training, but those who become adept at it can accomplish extremely complicated tasks such as riding a bike and playing video games. When blind people echo-locate, the sound information is processed in visual rather than auditory parts of the brain.
The brains of deaf people also show major plastic changes. In hearing people, sound information from the ears is processed by the auditory cortices in the temporal lobes. In people who are born deaf, however, these same brain areas are activated in response to visual stimuli. Deaf people also appear to have enhanced peripheral vision. This is linked to an increase in the overall area of the optic disc, where fibers of the optic nerve exits the eye on their way to the brain, and to thickening around its edges; it also suggests that the “where” stream of the visual pathway is stronger. Neuroplasticity in deaf people is not confined to the visual and auditory systems.
Once thought to be extremely rare, synesthesia is now believed to be relatively common, and may be experienced by one in every hundred people, or more. More than 40% of synesthetes have a relative with the condition, indicating that genetics plays a big role. {with how we can already genetically pre-order babies, if we are able to figure out more specifically the genetica linkages, could we make people where they almost experience reality in a different dimensional sense if they have one, or multiple synesthete associations?}With training however, non-synesthetes can learn to associate letters with colors or sounds, so that they evoke synesthetic experiences, and it is likely that this learning also occurs as a result of cross-modal plasticity. {could VR help this training? What does this training look like?}
The human brain is an organ of staggering complexity, containing 86 to 100 billion neurons, an even larger number of glial cells, and something on the order of a quadrillion exquisitely precise synaptic connections. Proper functioning of the nervous system depends upon all of these connections forming correctly; but how does such a complex organ develop? It has evolved a strategy of high redundancy- that is, the developing brain produces far more nerve cells than it actually needs but kills many of them off, and those that survive go on to form an overabundance of synaptic connections before pruning back the misguided or otherwise exuberant ones. These processes are governed by genetics but are highly dependent upon environment and experience during the early postnatal period, factors that fine-tune the neuronal circuits as they are being laid down.