W.S. McCulloch and J.G. Dusser de Barenne


Changes in action potentials, afterpotentials and pH shown to be factors for facilitation and extinction at the site of stimulation and in neighboring cortical foci have been demonstrated in distant parts of the central nervous system.

The effects of these changes in remote parts of the central nervous system belonging to the system stimulated were studied by eliciting the knee-jerk periodically and stimulating a cortical focus for extension at the knee with facilitating or extinguishing stimulation. Stimulation giving primary facilitation at such a focus facilitates the knee-jerk; stimulation giving extinction at this focus extinguishes the knee-jerk. Precise thermo-coagulation of this same focus promptly abolishes the knee-jerk which returns very late and small.

The effects of these changes in remote parts of the central nervous system pertaining to systems reciprocally related to the extensor systems involved in the knee-jerk were studied by stimulating a cortical focus for flexion at the knee. Extinguishing stimulation of such a focus enhances the knee-jerk; facilitating stimulation of that focus obliterates the knee-jerk. This last phenomenon is a true central inhibition in that it is one aspect of reciprocal innervation. In this it differs from extinction which does not depend upon any change in a reciprocally related system, although inhibition must ultimately depend upon factors for extinction in the system under investigation due to excitation in the reciprocally related system.


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Keywords: Changes, System, Knee-Jerk, Potentials, Stimulation, Foci, Extinction, Science

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1 Reprinted from The American Journal of Physiology. Vol. 126, No. 3, p. P570, July, 1939
2 From the Laboratory of Neurophysiology, Yale University School of Medicine, NewHaven, Conn.