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Neurons, mainly found within the cortex, are nerve cells which send action potentials from the axon hillock (a small protrusion) to the axon terminal that joins with the synapse. When an action potential is fired, a neuron becomes depolarised, meaning that it experiences a shift in its membrane potential (the electrical potential difference across the plasma membrane). This shift makes it easier for the action potential, which consists of positively charged ions, to come through. The time taken for this process varies drastically, but neurons can be fired up to 200 times per second.

Each hemisphere of the brain can be divided into four subsections. The frontal lobe is the largest lobe; located at the front of the head, it dictates personality, speech production, and problem-solving skills. The temporal lobe is located on the lateral extremities of the brain, and is involved in auditory processing, language recognition, and short-term memory. The parietal lobe is located in the midbrain; it is used for spatial relationships, pain reception, and touch interpretation. The occipital lobe is found in the back of the brain and is involved with vision processing. The cerebellum, otherwise known as the ‘little brain’, is responsible for balance and automatic functions. There are also many smaller components, such as the hypothalamus and the amygdala.

Neuroplasticity is the brain’s capacity to reorganise its structure, functions, or connections based on stimuli. It is studied especially during strokes or TBI (traumatic brain injury) recovery, as measuring brain activity during these periods is crucial. There are two subsections to neuroplasticity: structural and functional reorganisation.

Structural reorganisation is an umbrella term used to describe any change in neuronal connections. New connections are constantly being made, strengthened, and lost; each time, this changes the physical structure of the brain tissue. This happens especially at infancy, when the brain is extremely active. By the time we are adults, we have half the number of synapses, due to a process known as synaptic pruning. Functional reorganisation, meanwhile, occurs when existing neurons propagate and form connections; this often happens following injury to compensate for the loss of function of damaged neurons. That injury could be physical (e.g., a stroke) or mental (e.g., the brain sometimes protects itself by rewiring the neurons surrounding the amygdala following a traumatic event during childhood).