A method for the study of the effects of combining multiple pseudorandom fusimotor stimulation on the responses of muscle-spindle primary-ending afferents

We describe a new method of investigation of the integrative action of fusimotor inputs in mammalian muscle spindles by stimulation of multiple fusimotor axons using independent pseudorandom pulse trains, each of low mean rate with pseudorandomly distributed stimulus intervals. Technically it was feasible only because of the development of (1) a novel, highly efficient approach to functional isolation of fusimotor efferents in ventral-root filaments, which we have called the isodyne strategy; (2) a real-time, microprocessor-based stimulus artefact cancellation device (SACAD); and (3) a highly adjustable, multi-branch stimulation electrode array. The general approach of using multiple, independent, pseudorandom stimulation of several input channels has wider applications in controlled-activation paradigms.