A Behavioral analysis of complete unilateral section of the pyramidal tract at the medullary level in macaca mulatta

Abstract

Ten Macaca mulatta monkeys were operantly conditioned to perform three motor paradigms designed to evaluate single and combination finger movements. Eight of these monkeys were retested after left medullary pyramidotomy; 2 monkeys underwent left medullary pyramidotomy prior to conditioning. All animals were tested for three years after operation. Monkeys with a completely sectioned medullary pyramid could, with time, perform difficult motor paradigms that required: (1) both individual and combination finger movements; (2) proximal upper extremity motor control; (3) thumb and index finger pincer grasp; and (4) the ability to preprogram and then execute a precision hand movement. The greater the extent of pyramidal tract destruction, the longer the time necessary for recovery of both discrete finger movement and pincer grasp, the greater the effort needed to attain recovery of hand function, and the weaker the affected musculature. The 2 animals in which pyramidotomy of at least 70% of the tract preceded efforts at operant conditioning learned and performed difficult motor paradigms. In all animals, neurological examination revealed that the most enduring and functionally most important deficit that interferes with hand function following pyramidotomy is loss of contactual hand orienting responses and failure of reflex sensorimotor adjustments.

Endogenous Neurogenesis Replaces Oligodendrocytes and Astrocytes after Primate Spinal Cord Injury

“…The pattern of recovery from injury to the brains and spinal cords of nonhuman primates parallels, in some respects, observations in humans: complete or extensive lesions of a system are rarely followed by substantial functional recovery, whereas partial lesions are often accompanied by a substantial degree of functional recovery (Turner, 1891;Mott, 1892;Mettler, 1944;Lassek and Anderson, 1961;Kuypers, 1974;Schwartzman, 1978;Little and Halar, 1985;Roth et al, 1991;Nathan, 1994;Coleman and Geisler, 2004) that is paralleled by systems-level plasticity (Netz and Homberg, 1997;Marshall et al, 2000;Schmidlin et al, 2004). Partial lesions that spare some pathways provide a potential substrate for subsequent spontaneous plasticity in the form of sprouting of spared axons or modified use of spared projections, which could lead to functional improvement.…”

Cross‐correlation analysis of motor unit activity recorded from two separate thumb muscles during development in man.

“…In the present study, we found that the average firing rate of the units in the thumb abductor muscles, for a contraction of 10-20% MVC, was about 16 Hz over the age range 4-11 years and then decreased with increasing age until the adult value of about 13 Hz was reached. Such a change in motor unit discharge frequency with age would not have contributed to the observed change in motor unit discharge synchrony since the chosen index of synchrony was standardized to a reference discharge frequency of 10 Hz (Harrison et al 1991 (Lawrence & Kuypers, 1968;Passingham, Perry & Wilkinson, 1978;Schwartzman, 1978). In man, following such a lesion, synchrony may be absent (Farmer et al 1993).…”

A Unilateral Section of the Corticospinal Tract at Cervical Level in Primate Does Not Lead to Measurable Cell Loss in Motor Cortex

“…In particular, investigations assessed the consequences of pyramidotomy, a lesion aimed at selectively interrupting the CS axons originating from one -or in the case of bilateral pyramidotomy -from both hemispheres (Beck and Chambers 1970;Bucy 1957Bucy , 1966Chapman and Wiesendanger 1982;Hepp-Reymond and Wiesendanger 1972;Hepp-Reymond et al, 1974;Kucera and Wiesendanger 1985;Lawrence and Kuypers 1968;Lawrence and Hopkins 1976;Schwartzmann 1978;Tower 1940;Woolsey et al, 1972). As reviewed in detail (Hepp-Reymond 1982), recovery after pyramidotomy in monkeys is variable and depends upon the precise location and extent of the lesion, post-lesion survival, and evaluation of types of movements and/or behaviour.…”