In the experiment, the rats’ spinal cords were completely severed, causing total paralysis of the hindlimbs.
They monitored the walking patterns of rats whose EES used the old, unvaried signal, and compared them to rats whose EES signals varied in their frequency, amplitude, and pulse duration on every step.
As the signal’s frequency was dialed up from 20 to 90 Hertz, the rats took larger steps, ranging from 2.9 to 6.8 centimeters in height.
Modulating the frequency helped the rats to walk longer: Rats whose EES continually pumped out 40 Hz signals eventually collapsed when their muscles stopped responding, whereas rats whose EES frequency varied were able to walk 1,000 steps to the end of the test – almost double the distance of the 40 Hz rats, on average.
The new turning algorithm also helped the rats to overcome more complicated obstacles, in the form of rodent-sized staircases whose steps ranged from 1.3 to 3.5 centimeters.
Because the frequency modulation helped the rats to take larger steps, those rats had a much easier time walking up the staircases.
They climbed the staircases successfully in 99 out of 100 attempts, whereas the rats who used the old technology “Tumbled against and failed to pass the lower staircase.”