Speed Heals: Both the rate and direction of axon growth in the spinal cord can be controlled Abstract: Both the rate and direction of axon growth in the spinal cord can be controlled, according to new research by USC College professor Samantha Butler and her collaborators. The study by Butler; lead researcher Keith Phan and graduate students Virginia Hazen and Michele Frendo of USC College; and Zhengping Jia of the University of Toronto, was published online in the Nov. 17 issue of the Journal of Neuroscience.