Operant conditioning of primate triceps surae H-reflex produces reflex asymmetry

Summary

Monkeys are able to increase or decrease triceps surae H-reflex when reward depends on reflex amplitude. Operantly conditioned change occurs over weeks and produces persistent alterations in the lumbosacral spinal cord which should be technically accessible substrates of primate memory. Previous work monitored and conditioned triceps surae H-reflex in one leg. To determine whether H-reflex conditioning in one leg affects the control leg, the present study monitored H-reflexes in both legs while the reflex in one leg underwent HR↑ or HR↓ conditioning. Under the HR↑ mode, H-reflex increase was much greater in the HR↑ leg than in the control leg. Under the HR↓ mode, H-reflex decrease was confined to the HR↓ leg. By showing that conditioning of one leg's H-reflex produces H-reflex asymmetry, the data further define the phenomenon and indicate that the other leg can serve as an internal control for physiologic and anatomic studies exploring the sites and mechanisms of the spinal cord memory substrates.