Facilitation and Inhibition of Spinal Motoneurons

Monophasic pulse pair analysis of intracranial self-stimulation loci

“…While monopolar stimulation elicited peak responding at shorter CoT intervals than bipolar stimulation for diencephalic loci, no such differences were noted for met-mesencephalic loci. Deutsch (1964) initially postulated that differences in less responding as a function of e-T interval were due to the axonal refractory characteristics of less neurons, just as this technique differentiated the temporal summation (Eccles, 1964;Lloyd, 1946), the refractory (Erlanger & Gasser, 1937), and the latent addition (Lucas, 1910) characteristics of individual peripheral nervous system neurons. In support of these data, Rolls (1971a) maintained that the absolute refractory period of less neurons was less than a e-T interval of 0.6 msec, since the current necessary to support a predetermined criterion less rate had to be increased to a maximal value when either the T pulses were omitted or when the e-T interval was less than 0.6 rnsec.…”

“…Moreover, diencephalic sites produced peak ICSS responding at shorter CoT intervals when cathodal and anodal sources were distant than when they were adjacent; the relative proximity of cathodal and anodal sources did not affect met-mesencephalic ICSS behavior. These results suggest that alterations in ICSS responding across CoT intervals are due to differences in the locus and density of ICSS neurons in the cathodal field and the presence and/or absence of adjacent anodal influences as well as the refractory characteristics of the ICSS neurons.The monophasic stimulation technique was initially employed to determine the refractory characteristics of peripheral nervous system neurons (Erlanger & Gasser, 1937;Lloyd, 1946;Sherrington, 1906). A pair of brief (0.1 msec) monophasic rectangular electrical pulses, the first of which was designated the C pulse and the second, the T pulse, would be temporally varied with respect to one another (C-T interval) during stimulation of peripheral nerves, allowing the estimation of their conduction velocity and axonal refractory periods.…”

“…The monophasic stimulation technique was initially employed to determine the refractory characteristics of peripheral nervous system neurons (Erlanger & Gasser, 1937;Lloyd, 1946;Sherrington, 1906). A pair of brief (0.1 msec) monophasic rectangular electrical pulses, the first of which was designated the C pulse and the second, the T pulse, would be temporally varied with respect to one another (C-T interval) during stimulation of peripheral nerves, allowing the estimation of their conduction velocity and axonal refractory periods.…”

Asymmetric interjoint feedback contributes to postural control of redundant multi-link systems

“…At the lowest level, the stretch reflex (Sherrington, 1898) has been considered to provide spring-like or servo-like control of an individual muscle (Merton, 1953;Nichols & Houk, 1976). Feedback from individual muscle spindles was subsequently shown to excite motoneurons of synergistic muscles and to inhibit motoneurons of antagonists (Liddell & Sherrington, 1925;Lloyd, 1946), giving rise to the concept of a myotatic unit comprised of both agonists and antagonists to provide servo-like control of individual joints (Merton, 1953). However, in human subjects, reflex control does not mimic a servo-like system (Crago, Houk & Hasan, 1976), and similarly, in cats the variation in intermuscular feedback gains measured in vivo varies among muscles crossing a single joint (Nichols, 1989).…”

Communications

“…(2) pH-variations have effects upon the entry-rates of NO3, I and Lloyd (1941Lloyd ( , 1946 described the time course of monosynaptic facilitation and direct inhibition produced by synchronous group IA afferent volleys on synergist and antagonist motoneurones, respectively. Direct PHYSIOLOGICAL SOCIETY, 16-17 JULY 1965 Monosynaptic facilitation had its maximal action at 'zero' interval.…”