Neuroplasticity, also called brain plasticity or brain malleability is the brain's ability to reorganize itself by forming new neural connections throughout life. The term “Neuroplasticity” was first used by a Polish Neuroscientist named Jerzy Konorski, who suggested that over time neurons that had 'coincidental activation due to the vicinity to the firing neuron would after time create plastic changes in the brain'. The brain has a lifelong capacity to change and rewire itself in response to the stimulation of learning and experience. Neurogenesis occurs, which is the ability to create new neurons and connections between neurons throughout a lifetime. As the neurons sprout branches and form synapses, some of these synapses strengthen and others weaken. Eventually, some unused synapses are eliminated completely, a process known as synaptic pruning, which leaves behind efficient networks of neural connections.
As we age, the rate of change in the brain, or neuroplasticity, declines but does not come to a halt. Neuroplasticity allows the neurons (nerve cells) in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment. Brain reorganization takes place by mechanisms such as "axonal sprouting" in which undamaged axons grow new nerve endings to reconnect neurons whose links were injured or severed. Undamaged axons can also sprout nerve endings and connect with other undamaged nerve cells, forming new neural pathways to accomplish a needed function.
A nerve cell with adjacent pathways. Image taken from pixabay.com . Copyright free.
Information in the brain is transmitted from neuron to neuron through specialized connections called synapses and a fundamental property of neurons is their ability to modify the strength and efficacy of synaptic transmission through a diverse number of activity-dependent mechanisms. A synapse between two neurons is made up of presynaptic and postsynaptic terminals, which are separated by a synaptic cleft. Neurons modify the strength of existing synapses, as well as form new synaptic connections and this is how neuroplasticity occurs. It also includes changes in strength of mature synaptic connections, as well as the formation and elimination of synapses in adult and developing brains. Hence, neuroplasticity can be defined as “The ability of the Central Nervous System to undergo structural and functional change in response to new experiences” or “The capacity of the nervous system for adaptation or regeneration after trauma”.
Plasticity is the mechanism for encoding, the changing of behaviours, and both implicit and explicit learning. It is hugely influenced by experience.
There are three main types of plasticity that shape the developing brain:
1. Experience-independent plasticity is pretty much everything that happens with the brain during the prenatal developmental phase. Neuronal connections and brain formation are processes driven by complex genetic instructions. There is an overproduction of neurons and that is why a due course of life we have most of our neurons when we are the youngest and then gradually start losing grey material.
2. Experience-expectant plasticity which is independent of external factors helps the neurons to connect to each other independent of other processes.
3. Experience-dependent plasticity can be seen throughout the life of every animal. Brain changes when different situations occur moving to new territory, when learning problems or suffering from injury. Those are the daily challenges for all living creatures which could either increase or decrease synapse numbers and make some brain areas bigger than others.
Other circumstances of neuroplasticity include changes in the body, such as the loss of a limb or sense organ, that subsequently alter the balance of sensory activity received by the brain. It is also employed by the brain during the reinforcement of sensory information through experience, such as in learning and memory. It aids brain recovery after the damage produced by events like stroke or traumatic injury where the brain compensates for lost activity.
Behavioural techniques or brain-machine interfaces can be used to harness the power of neuroplasticity for therapeutic purposes such as specific exercise training, cognitive training and neuropharmacology. Furthermore, neuroplasticity can also be pivotal in physical neurorehabilitation where the brains' ability to create and lay down new pathways can be utilized to enhance brain and neuromuscular adaptation.
Image taken from pixabay.com. Copyright free.
References:
1. Shiel Jr., MD, FACP, FACR, William C. “Medical Definition of Neuroplasticity.” MedicineNet, 24 Jan. 2017, www.medicinenet.com/neuroplasticity/definition.htm.
2. “Neuroplasticity.” Physiopedia, www.physio-pedia.com/Neuroplasticity. Accessed 14 Dec. 2020.
3. Rugnetta, Michael. “Neuroplasticity.” Britannica.Com, Encyclopædia Britannica, 3 Sept. 2020, www.britannica.com/science/neuroplasticity/Cross-modal-reassignment.
Comments