Wednesday, December 12, 2007

History of Neuroplasticity

Matthias, I agree. And thanks for introducing Dean Kamen. Seems pretty clear his work designing arm prostheses that can "feel", will make the wider PT/OT rehab role lots easier. :)

You highlighted him as a good example of someone who is not afraid of "learning" and gave some of the important characteristics of that:
"creativity, an ability for lateral thinking, the ability to make connections between seemingly unrelated fields (of science) - and disrespect for authority."

I agree although I would translate "disrespect for authority" into "an ability to recognize and bypass conventional dogma or "groupthink" in favor of considered scientific reflection of all possibilities."

On the topic of neuroplasticity, Sharon Begley, in her book Train Your Mind, Change Your Brain, recounts how difficult it is for dogma to be overturned in favor of counter-information. She traces the history of the scientific study of neuroplasticity starting with William James, who said, in 1890: "organic matter, especially nervous tissue, seems endowed with a very extraordinary degree of plasticity", meaning, according to Begley, "a structure weak enough to yield to an influence". No one picked up on this at the time. Ramón y Cajal was in the forefront of neuroscience, and had dazzling, substantive, convincing and irrefutable research work to offer up. His opinion on fixedness, immutability, unchangingness in the nervous system was pretty much conflated with his actual research for the next century.

In the 1940's, Donald Hebb at McGill came up with
"When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased"

..which became known as Hebbian learning, and gave rise to the quip, "Neurons that fire together wire together."

Along came researchers like Fred Gage (a shirttail relative, apparently, of the famous Phineas, according to Begley), who runs a lab at the Salk Institute in La Jolla, California.

Starting in the 1960's, other researchers, like Joseph Altman at MIT, Michael Kaplan at Boston U., and Fernando Nottebohm who studied birds that produce new songs continually throughout their lives, William Greenough, showed evidence that went against dogma, but weren't able to budge it. Elizabeth Gould showed in the 1990's that primates demonstrated neurogenesis. Slowly, the dogma finally started to dissolve.

Then researchers tried to figure out how to show neuroplasticity exists in the human brain - they wanted to know not just if the human brain could rewire itself, but also if it could grow new cells. It was hard to deal with all the ethical dilemmas involved, but they finally got permission to look at brains of a group of people who were terminally ill, at autopsy. Specifically, Peter Eriksson and Fred Gage worked together to determine that new neurons are born constantly, even in the brains of old and sick humans. You can read more about how the dogma was made to melt down in this history module.

Suffice it to say, human neuroplasticity is a fact of life, and cannot be pushed back into the shadows. From a physiotherapist point of view, this is good news! It shows that our work, i.e., helping people, helping patients in pain, bolstering them and supporting their efforts to improve, now has irrefutable science to back it. Now we can show people studies (should we have to) to prove they can recover from even the most debilitating injury, but even more so we can turn around and challenge various dogmas that still exist right in our own profession, dogmas about pain and how best to help relieve it, help move the profession from one that is still mesmerized by structure into one that smoothly understands and supports function.

1 comment:

Manuele said...

Thank you for your discussions and insights into the history of neuroplasticity.

You may also be interested to read more about Roszenweig's study in 1984 with rats. Through post-mortem examination, he found that rats raised in an "enriched environment," multi-level living areas filled with ladders, wheels, many more rats and other rich opportunities for interaction developed larger neurons with a greater number of synaptic connections (in cerebral cortex I believe) than those in the "impoverished" environment with much simpler living conditions and fewer things to manipulate or explore.

Keep up the work!