William James "Principles of Psychology" and Brain Plasticity

Question

I am reading William James' "Principles of Psychology". It is clear in his research that he was acutely aware of brain plasticity and the limited capacity for a precise "schema" (ie. static brain map) to represent brain function. Seeing that this text is well over 100 years old and cites much research even older, how is it that I see so much information (primarily in the press and lay neurology texts) that brain plasticity is a new perspective recently discovered by academics and researchers? Without question the earliest modern neuroscientists knew about brain plasticity. It was an undeniable characteristic of their research. (As a side note, it is interesting that creatures with less intelligence have greater plasticity, with the level of intelligence being inversely proportional to plasticity. A fact I've never seen discussed.)

I feel I should mention that I am not a psychologist or neuro-scientist. I have a doctorate in Statistics. I did search academic papers and there are many papers that credit William James with describing plasticity under the heading "habit". So to my original question, why is it that plasticity is just being "discovered?"

An academic paper that clearly sites William James with being the first to introduce plasticity - https://fastertomaster.com/the-brain-that-changes-itself-norman-doidge/

A recent book that erroneously claims plasticity is a new concept - https://fastertomaster.com/the-brain-that-changes-itself-norman-doidge/

Answer 1

Short answer
Neural plasticity is a broad term. While it has long been recognized, the fact that the adult brain is plastic even at the gross structural level has taken a long time to become widely accepted.

Background
There are a few things that play a role here.

• First and foremost, neural plasticity is a term encompassing many different processes. Neuroplasticity can be observed from microscopic (molecular) changes in individual neurons, to large-scale structural changes, such as cortical remapping in response to injury.
• Secondly, the small scale changes have long been recognized, the gross structural changes were only discovered much later.
• Thirdly, neuroplasticity has indeed been long recognized, but it has long been thought that there were critical periods in life (Sylva et al., 1997) where after plasticity was no longer present. In a way, that idea is still recognized, and is the reason why, e.g., congenitally deaf children are receiving cochlear implants in the first months of their lives to allow the plastic brain to develop hearing and speech development during this "critical period" where these developments are accompanied by gross changes in the brain not possible later in life (Snik et al., 1997). Untreated prelingual deafness therefore results in impaired speech understanding and the typical 'deaf speech' when they receive an implant after this critical period. Paul Bach-y-Rita and Michael Merzenich are often credited for their ideas on the plastic adult brain. For instance, Bach-y-Rita recognized that his dad, by then an aged man, was still capable to re-learn many tasks after serious brain injury. He recognized that hence, the adult brain is plastic too (plastic, in terms of gross changes that allow re-allocation of healthy brain tissue to take over the tasks from damaged regions). The idea of the adult brain being able for gross plastic changes has taken a while to become accepted.

<sub>References
- Snik et al., Int J Ped Otorhinolayngol (1997); 41(2):121-31
- Sylva et al., Br Med Bull (1997); 53(1): 185-19</sub>

Answer 2

The difference is that these days - it is known that plasticity (mainly) occurs in the synaptic connections, - the biophysical changes that implement the plasticity are known. - this knowledge allows manipulating and blocking of memory formation.

For instance in the 60s is was still thought that memory was stored in DNA.