ON THE QUESTION OF THRESHOLD IN STIMULATION OF THE MOTOR CORTEX

Abstract

By use of graded stimuli and known frequencies, single points within the motor cortex of cats and of young macaques demonstrated the deviation, reversal and facilitation of Sherrington, as well as "centripetal indi-viduation." Movements elicited by frequencies of 30 cycles or less showed a prolonged latent period and slowing of time to attain maximal contraction. Below 20 cycles the total movement characteristic of the cortical point stimulated was not reproduced from the year-old macaque,[long dash]a phenomenon not noted in the cat''s motor cortex. Above 500 cycles the movement was not fractional if the threshold were reached; the latent period was increased but the character of movement was unchanged.