The Central Pattern Generator

In Dr. Neal’s presentation, she illustrated that conceptual processing uses multiple representations: linguistic representations in the brain's language systems and situated simulations in the brain's modal systems (LASS). While linguistic representations can be sufficient for some performances that are "superficial", simulations represent deep conceptual information that are said to activate automatically and quickly. While referencing the article “fMRI evidence for word association and situated simulation in conceptual processing” by Simmons and colleagues, Dr. Neal continues to express that conceptual processing relies heavily on both language and situated stimulation; however, she does not go into great detail in regards to what happens if a brain area for one of these systems is lesioned or damaged. With the help of other studies referenced in the article, a large point was made that words access the linguistic information first, prior to accessing conceptual information. However, since conceptual information represented in simulations can be activated automatically, is it possible that information moves past the linguistic information and reaches the situated simulations directly?

A similar concern arose in Susan Harkema’s clinical case study. In the article “How a Revolutionary Technique Got People with Spinal-Cord Injuries Back on Their Feet,’ Harkema, a neurophysiologist at the University of Louisville, conveyed how voluntary movement was made possible through stimulation in individuals with incomplete/complete motor loss to their lower extremities. Harkema was astonished to see that a client could wiggle his toes after being told four years prior he would never be able to move his lower body again. At first, Harkema knew it wasn’t possibly a voluntary movement, but she was proved wrong when the client could move his toes in the directions Harkema asked him to. The study of this type of movement all began with studying cats on treadmills. Cats that had their spinal cord severed were suspended over a treadmill and trained to walk in a stepwise motion, guiding their legs.This idea was called a central pattern generator as the spinal circuitry was able to propel the cats forward to control movements without input from the brain. It was later that Harkema and colleagues furthered their studies and began using stimulation to start training the body to produce more voluntary movements. 

Harkema was able to show that even when an essential step to the process is removed, some mobility/activity can be brought back through stimulation and training. If the brain functions in a stepwise function for conceptual learning, it would be interesting to see if stimulation and training similar to this could be implemented to improve activity after a lesion.


Resources:
Willyard, Cassandra. “How a Revolutionary Technique Got People with Spinal-Cord Injuries Back on Their Feet.” Scientific American, Scientific American, 7 Aug. 2019, www.scientificamerican.com/article/how-a-revolutionary-technique-got-people-with-spinal-cord-injuries-back-on-their-feet/.