What is Neuroplasticity? – A Simplified Guide
Neuroplasticity is a neuroessentialism buzzword used by motivational speakers, self-help gurus, and the pharmaceutical drug industry to support dubious interventions that ‘rewire your brain’. But, unfortunately, the word neuroplasticity is ill-defined. So, what did neuroplasticity initially mean, and how do researchers define neuroplasticity today?
Neuroplasticity is best defined as the ability of the nervous system to change its activity in response to intrinsic or extrinsic stimuli by reorganising its structure, functions, or connections. [Mateos-Aparicio & Rodríguez-Moreno, 2019]
These changes can either be beneficial (restoration of function after injury), neutral (no change), or negative (can have pathological consequences).
Neuroplastic changes can be divided into three depending on whether they occur at a molecular, cellular or synaptic level.
- Neuroplastic changes occur via signalling pathways.
- Ca2+/calmodulin-dependent protein kinase (CaMK2), extracellular regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAP)/ERK, and the brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) are examples of signalling pathways.
- Changes can be structural or functional
- Structural plasticity includes neuronal plasticity, dendritic plasticity, and synaptic plasticity.
- Synaptic strength is related to learning and memory formation.
- When it increases, it is known as long-term potentiation (LTP)
- When it decreases, it is called long-term depression (LTD).
Neuroplasticity can be broken down into two major mechanisms: [Puderbaugh & Emmady, 2021.]
1. Neuronal regeneration/collateral sprouting:
- This includes concepts such as synaptic plasticity, dendritic plasticity and neurogenesis.
2. Functional reorganisation:
- Concepts such as equipotentiality, vicariation, and diaschisis
- Vicariation involves the ability of one part of the brain to substitute for the function of another.
- Equipotentiality postulates that all parts are equivalent for the mediation of function within a given cortical association area. Thus, each portion of any given region can encode or produce the behaviour usually controlled by the entire region. Thus, the remaining area compensates for incomplete damage within a zone.
- Diaschisis refers to the functional changes in brain structures remote from the site of focal brain damage. Diaschisis is a concept that damage to one part of the brain could cause a loss of function in another area due to some connected pathway.
The first mention of the term plasticity in regards to the nervous system was made by William James in 1890. However, the term neural plasticity/ neuroplasticity is credited to Jerzy Konorski in 1948 and was popularised by Donald Hebb in 1949.
- Although the brain was considered stable and unchanging during adulthood, Raisman used Electron microscopy (EM) to show that morphological reorganisation of neuropil was possible following a selective lesion. [Raisman 1969]
- Today, researchers use neuroplasticity as an umbrella term to describe any adaptive changes to the nervous system’s structure, function, and connectivity. It is now clear that adult neurons can respond and adapt to intrinsic and extrinsic factors such as neurotransmitter fluctuations, hormones, emotions, and behaviours throughout life.
In summary, neuroplasticity is essential for learning and memory processes that allow an organism to learn and adapt to its environment. At present, there is considerable interest to harness evidence-based interventions in clinical practice to improve human wellbeing and longevity.