“This video is from an early computer graphics film made by Steve Raymond and Paul Pangaro at the MIT Research Lab of Electronics in 1975. The film quantifies how the nerve impulses that travel along nerve axons change the excitability of the membrane. Findings from experiments with frog axons are presented in a progression, leading to the hypothesis that such changes in excitability cause impulse patterns to be distributed within the nervous system according to the messages encoded in spike trains. Jerome Y. Lettvin and colleagues championed the idea that excitability changes underlie neural encoding and decoding of meaning by sensory systems.”