Neuroplasticity refers to the brain’s ability to remap itself in response to experience. The theory was first proposed by Psychologist William James who stated “Organic matter, especially nervous tissue, seems endowed with a very extraordinary degree of plasticity". Simply put, the brain has the ability to change. He used the word plasticity to identify the degree of difficulty involved in the process of change. He defined plasticity as "...the possession of a structure weak enough to yield to an influence, but strong enough not to yield all at once" (James, 1890).
The brain consists of both neurons and glia cells. The neurons, which are cells housed in a cell body called a Soma, have branches which extend from them, referred to as dendrites. From these dendrites extend axons which send and receive impulses, ending at junction points called synapses. It is at these synapse points that the transfer of information takes place.
At the heart of Neuroplasticity is the idea of synaptic pruning. It is the ability to prune away unused connections, as well as to form new connections. The term is probably best explained in the aphorism, “Neurons that fire together, wire together” (Doidge, 2007, p. 63). The idea being that if two or more neurons fire simultaneously on a continual basis, they will eventually fire on the same cortical map, thus strengthening the connection. The reverse is true in that if two or more neurons begin firing separately, they will eventually form separate cortical maps. In the words of Donald Hebb:
"The general idea is an old one, that any two cells or systems of cells that are repeatedly active at the same time will tend to become 'associated', so that activity in one facilitates activity in the other" (Hebb, 1949).
"When one cell repeatedly assists in firing another, the axon of the first cell develops synaptic knobs (or enlarges them if they already exist) in contact with the soma of the second cell" (Hebb, 1949).
The first use of the term neuroplasticity was by polish neuroscientist Jerzy Konorski in 1948. The idea had been proposed in 1890 by William James but it had a long way to go to overcome the mechanical viewpoint that was central to the understanding of neuroscience during that time (LeDoux, 2002).
Hebb & Freud
In 1949 Donald Hebb proposed the idea that when two neurons fired together repeatedly in time, the relationship between them changed. He proposed that assimilation took place (Hebb, 1949). He inferred from this that neuronal structure could be altered by experience. As new an idea as this was, it was not altogether new. It was Freud who first proposed such an idea calling it the law of association by simultaneity. He did this in 1888 (Doidge, 2007, pp. 63,334).
Monkey's, Fingers, and Mapping
“Of neuroplasticians with solid hard-science credentials, it is Merzenich who has made the most ambitious claims for the field: that brain...