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PubMedDate not supplied

Encoding of motor parameters by corticomotoneuronal (CM) and rubromotoneuronal (RM) cells producing postspike facilitation of forelimb muscles in the behaving monkey.

This paper compares the properties of corticomotoneuronal (CM) and rubromotoneuronal (RM) cells identified by postspike facilitation (PSF) of rectified EMG activity in the awake monkey. The postspike effects of CM and RM cells in flexors and extensors of the wrist and fingers have been determined, as have the discharge properties of these cells in relation to alternating ramp-and-hold wrist movements. The characteristics of postspike facilitation and postspike suppression (PSS) were similar for RM and CM cells. The magnitude of RM-PSF was weaker than CM-PSF and RM cells showed a stronger preference for facilitation of extensor muscles than CM cells. As with CM cells, the onset of discharge in RM cells preceded the onset of EMG activity in their target muscles. Tonic discharge related to static torque was more prominent in CM cells, whereas phasic discharge was more prominent in RM cells; however, many RM cells showed some tonic activity weakly related to static torque. We conclude that CM and RM cells share many common features; however, RM cells are concerned primarily with the dynamics of muscle contraction.

Animals↗
PubMed1996

Skilled forelimb movements in prey catching and in reaching by rats (Rattus norvegicus) and opossums (Monodelphis domestica): relations to anatomical differences in motor systems.

Traditional anatomical/behavioral classifications suggest that rats and opossums have simple motor systems and are impoverished with respect to their ability to make prehensile movements. Nevertheless, the motor system in rats and opossums represent extremes in relative size and complexity suggesting that a behavioral analysis of the movement competencies of these species will provide insights into the significance of such anatomical differences. This paper examines the movements that the two species use in catching crickets and in reaching for food items. Both species could use a single limb to reach out and grasp prey during prey catching and both could use a single limb to take food from a shelf. Both species could transport the food to the mouth by using a single paw. The food handling behavior of the rats was more complex than that of the opossums, however. They used a variety of prey catching movements and extensively manipulated the prey to remove the legs and wings before eating only the head and body. Additionally the rats made rotatory limb movements of aiming, pronation, and supination, when reaching. For both cricket catching and reaching, they used their digits more than did the opossums. The suggestion also emerged from the results that the movements of the opossums were more fixed and species-typical whereas those of the rats were more plastic and individualistic. Thus, the skilled movements of both species are more complex than is generally recognized and the greater complexity of the rat movements parallels their more complex motor system. These results are discussed in relation to anatomical differences in the motor system and, specifically, to differences in the terminal fields of the pyramidal tract. It is concluded that the motor abilities of nonprimate mammals have been vastly underrated.

Animals↗
PubMed1987

Neuronal activity in nuclei pontis and reticularis tegmenti pontis related to forelimb movements of the monkey.

The activity of the pontine nucleus (PN) neuron was recorded in 3 monkeys moving a handle alternately from start to target zones in a simple extension-flexion movement at the wrist. Of 73 PN neurons related to the task, 44 were related to movement, 19 to handle holding and 5 to both movement and holding of the handle. Of the 44 movement-related neurons, 16 were related to flexion, 22 to extension, and 6 to both. In 37 of 54 analyzed movements of the PN neurons which were related to movements, or to both movements and handle holding, the change of the activity occurred before the movement. However, in most of these cases (24/37), discharge occurred less than 100 ms earlier than the start of the movement. In the remaining one-third of movements (17/54), neurons discharged after the onset of the movement. Locations of the 73 neurons were histologically verified in the pontine nucleus. Somewhat similar observations were made of 14 cells located in the nucleus reticularis tegmenti pontis (NRTP). Considering that the majority of movement-related PN and NRTP neurons discharged immediately before or even after the onset of movement, these neurons may play a role in the execution of movement, at least of a simple movement, rather than in the initiation or planning of movement.

Animals↗
PubMed1984

The possible participation of a dopaminergic system in mutilating behavior in rats with forelimb deafferentation.

Partial rhizotomy (section of dorsal roots C5 to Th 1 included) leads to abnormal mutilating behavior in the rat, presumably due to pain sensation in the deafferented limb. As dopamine (DA) has been shown to play a role in analgesia, destruction and stimulation of the ventral tegmental area (VTA) were used to check whether they induced an increase or a decrease in the mutilating behavior respectively. Destruction of DA neurons located in the VTA was performed by local administration of 6-hydroxydopamine whereas activation was achieved either by imposed electrical stimulation or by chronic oral administration of D-amphetamine sulfate. These 3 treatments accelerated the onset of the mutilating behavior and induced an extension of the mutilating wounds, D-amphetamine sulfate producing the most pronounced acceleration in their development. The results obtained after destruction of DA-VTA neurons fit well with the working hypothesis. The increase of the mutilating behavior rather than a decrease subsequent to the other treatments could have been caused by the hyperactivity and increase of chewing behavior induced by the less specific stimulating techniques.

Afferent Pathways↗
PubMed1985

Unexpected reorganization of somatosensory cortex in a raccoon with extensive forelimb loss.

Electrophysiological recordings were made from primary somatosensory cortex in a raccoon that had suffered a traumatic amputation of the forearm some time prior to its capture. Neurons in the affected forepaw region of sensory cortex were not silent but responded to cutaneous or neuroma activation of the remaining forearm stump. In addition, cells at many sites were responsive to tactile stimulation of the glabrous skin of the hindpaw ipsilateral to the damage. This indicates that the cortical plasticity following peripheral nerve damage can occur over much larger regions of cortex than was previously thought. An unmasking of silent thalamocortical terminals is not likely to be the mechanism underlying this plasticity in the raccoon.

Amputation, Traumatic↗
PubMed1990

Cervical interneurones oligosynaptically excited from primary afferents and rhythmically active during forelimb fictive locomotion in the cat.

In C6-C7, activity of neurones oligosynaptically excited from primary afferents was examined during fictive locomotion. Two kinds of neurones were found: neurones with activity modulated and with activity not modulated. The minimum linkage of the pathway to modulated neurones was mono- and disynaptic from muscle and cutaneous afferents, respectively, while non-modulated neurones were monosynaptically excited from both afferents. Modulated neurones were mainly located in the ventral part of the dorsal horn and adjoining intermediate region, non-modulated ones located in the dorsal horn. Modulated neurones were found near motor nuclei as well. Active periods of modulated neurones were widely distributed in the step cycle.

Afferent Pathways↗
PubMed1990

Last-order interneurones controlling activity of elbow flexor motoneurones during forelimb fictive locomotion in the cat.

Activity of C5-C7 last-order interneurones, which were identified by antidromic invasion from the elbow flexor motor nuclei, was examined during fictive locomotion. Three groups of neurones were found: one showing no rhythmic modulation of activity (non-modulated neurones), another rhythmically active mainly in phase with the target motoneurones (modulated neurones of group 1), the other out of phase with them (modulated neurones of group 2). Activity pattern suggested group 1 and group 2 neurones distributing excitation and inhibition to flexor motoneurones, respectively. Location of neurones seemed to be differentiated as well, group 1 located dorsally, group 2 ventrally in the gray matter.

Animals↗
PubMed1991

Last-order interneurones controlling activity of elbow extensor motoneurones during forelimb fictive locomotion in the cat.

Last-order interneurones, which were identified by antidromic invasion from the elbow extensor motor nuclei (triceps brachii), were examined for rhythmic activity during fictive locomotion. Last-order neurones with activity modulated were divided into 3 groups: one exhibited flexor-like activity, another extensor-like, and the third activity which had properties of both. Flexor-like neurones, presumably inhibitory, were located in the rostral segments (C6-C7), whereas extensor-like ones, presumably excitatory, were located in the caudal (C7-T1). Neurones of the third group were found in the most caudal segments (C8-T1). The results seem to suggest the existence of functional localization in the stepping generator.

Animals↗
PubMed1995

Oriented growth of regenerating axons in axolotl forelimbs is consistent with guidance by diffusible factors from distal nerve stumps.

Previous studies have shown that when peripheral nerves in axolotl limbs are cut and surgically misdirected, regenerating axons grow back to the original pathways and innervate their correct muscles. In the present study however, we demonstrate that when given a choice between their correct nerve stump and an incorrect stump (forearm flexor nerve), regenerating extensor cranialis nerve axons grow towards both pathways. This result suggests that the directed growth of regenerating axons in the peripheral nervous system may be in response to factor(s) released from the distal nerve stumps, but that in this region of the limb, axons were unable to differentiate between correct and incorrect pathways. Growing axons appeared to be accompanied by neural sheath cells, whilst activated macrophages remained near the cut nerve stumps. Possible mechanisms by which regenerating axons may eventually innervate their correct targets are discussed.

Ambystoma mexicanum↗
PubMed2004

Convergence of forelimb and hindlimb Natural Pendular Period in baboons (Papio cynocephalus) and its implication for the evolution of primate quadrupedalism.

The patterns of muscle mass distribution along the lengths of limbs may have important effects on the mechanics and energetics of quadrupedalism. Specifically, Myers and Steudel (J. Morphol. 234 (1997) 183) have shown that fore- and hindlimb Natural Pendular Periods (NPPs) may affect quadrupedal kinematics and must converge to reduce locomotor energetic costs. This study quantifies patterns of limb mass distribution in a live sample of Papio cynocephalus using limb inertial properties (mass, center of mass, mass moment of inertia, and radius of gyration). These inertial properties are calculated using a geometric modeling technique similar to that of Crompton et al. (Am. J. phys. Anthrop. 99 (1996) 547). The inertial properties in Papio are compared to those of Canis from Myers and Steudel (J. Morphol. 234 (1997) 183). The Papio sample has convergent fore- and hindlimb NPPs. Additionally, these limb NPPs are relatively large compared to those of Canis due to the relatively distally distributed limb mass in the Papio sample (relatively large limb masses, relatively distal centers of mass and radii of gyration, and relatively large limb mass moments of inertia). This relatively distal limb mass appears related to the grasping abilities of their hands and feet. Causal links are explored between limb shape adaptations for grasping hands and feet and the kinematics of primate quadrupedalism. In particular, if primates in general follow Papio's limb mass distribution pattern, then relatively large limb NPPs may lead to the relatively low stride frequencies already documented for primates. The kinematics of primate quadrupedalism appears to have been strongly influenced by both selection for grasping hands and feet and selection for reduced locomotor energetic costs.

Animals↗
PubMed1999

Wrist and digital joint motion produce unique flexor tendon force and excursion in the canine forelimb.

The force and excursion within the canine digital flexor tendons were measured during passive joint manipulations that simulate those used during rehabilitation after flexor tendon repair and during active muscle contraction, simulating the active rehabilitation protocol. Tendon force was measured using a small buckle placed upon the tendon while excursion was measured using a suture marker and video analysis method. Passive finger motion imposed with the wrist flexed resulted in dramatically lower tendon force (approximately 5 N) compared to passive motion imposed with the wrist extended (approximately 17 N). Lower excursions were seen at the level of the proximal interphalangeal joint with the wrist flexed (approximately 1.5 mm) while high excursion was observed when the wrist was extended or when synergistic finger and wrist motion were imposed (approximately 3.5 mm). Bivariate discriminant analysis of both force and excursion data revealed a natural clustering of the data into three general mechanical paradigms. With the wrist extended and with either one finger or four fingers manipulated, tendons experienced high loads of approximately 1500 g and high excursions of approximately 3.5 mm. In contrast, the same manipulations performed with the wrist flexed resulted in low tendon forces (4-8 N) and low tendon excursions of approximately 1.5 mm. Synergistic wrist and finger manipulation provided the third paradigm where tendon force was relatively low (approximately 4 N) but excursion was as high as those seen in the groups which were manipulated with the wrist extended. Active muscle contraction produced a modest tendon excursion (approximately 1 mm) and high or low tendon force with the wrist extended or flexed, respectively. These data provide the basis for experimentally testable hypotheses with regard to the factors that most significantly affect functional recovery after digital flexor tendon injury and define the normal mechanical operating characteristics of these tendons.

Animals↗