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PubMed2006

The roles of various projection areas of the motor cortex in the reorganization of the natural coordination of head and forelimb movements in dogs.

A food-related operant reaction was developed in dogs, in which animals had to maintain tonic elevation of the forelimb to hold a bowl while eating with the head tilted towards the feeder. The acquisition of this reaction involved rearrangement of the natural coordination of head and limb movements which appeared at an early stage of training of the dogs. Forelimb elevation was initially accompanied by anticipatory raising of the head, while lowering of the head led to lowering of the elevated limb. Limb elevation could only be maintained in the posture in which the head was raised. The new coordination required for obtaining food, contrary to the innate coordination and consisting of tonic elevation of the limb with the head lowered, could only be achieved as a result of training. Previous studies have established that lesioning of the primary motor cortex (MI) in the hemisphere contralateral to the working limb leads to stable impairment of the learned coordination, with regression to the initial coordination. The present report describes studies of the effects of local lesions of various projection areas of MI on performance of the learned coordination. Dogs which had acquired the learned operant reaction requiring the new head/limb coordination showed impairment only after lesioning of the representation area of the working limb in the MI; lesioning of the representation area of the head had no such effect.

Animals↗
PubMed1977

Dynamic relations between natural vestibular inputs and activity of forelimb extensor muscles in the decerebrate cat. II. motor output during rotations in the horizontal plane.

Decerebrate cats with the spinal cord sectioned at low thoracic levels were submitted to rotations in the horizontal plane. The position of the animal with respect to the axis of rotation was such that horizontal canal afferents were activated either alone or in combination with macular afferents. The EMG activity from the triceps brachii muscles of both forelimbs was recorded. The main findings were as follows. (1) The motor output to each forelimb extensor is increased by an increase in the activity of the horizontal canal afferents from the contralateral labyrinth. The phase of the motor output with respect to that of the vestibular afferents shows a lag which increases with frequency, reaching about 85 degrees at 1.0 Hz. (2) The macular and horizontal canal inputs are independently processed in the central nervous system and the motor output in response to both inputs applied simultaneously is a linear summation of the outputs expected for each of the inputs.

Acceleration↗
PubMed1981

Modulation of transmission in forelimb flexion reflex pathways by elbow joint afferent discharge in decerebrate cats.

In intact forelimbs in decerebrate cats, flexion reflexes are most easily elicited when the elbow joint is extended and extension reflexes are most easily elicited when the elbow joint is flexed. Abolition of sensory discharge arising from the elbow joint by intra-articular injection of local anaesthetic eliminates this modulation of reflex excitability. We conclude that elbow joint afferent discharge modulates the transmission in flexion reflex pathways to forelimb motoneurones.

Afferent Pathways↗
PubMed1984

Discharges of forelimb spindle primary afferents during locomotor activity in the decorticate cat.

In the acute decorticate cat, the discharge patterns of single spindle primary afferents from various forelimb muscles during locomotion have been examined in relation to the extrafusal activity. In a given muscle under isometric conditions, the activation of spindle primary endings was closely related to that of extrafusal muscle fibers. Since this increase in spindle discharge could occur in the absence of detectable electromyographic activity in the parent muscle, it resulted, at least to some extent from an enhanced activity in gamma efferents. The data are discussed in relation to previous studies of forelimb efferent activity and hindlimb fusimotor control in the same preparation.

Animals↗
PubMed1986

Transneuronal labelling of neurones projecting to forelimb motoneurones in cats performing different movements.

Electrophysiologically identified propriospinal neurones (PNs) in the C3-C4 segments mediate disynaptic excitation and inhibition from higher centres to forelimb motoneurones. In behavioural experiments it was shown that C3-C4 PNs can mediate the command for target-reaching. We have investigated if the C3-C4 PNs which project monosynaptically to forelimb motoneurones are specifically active during target-reaching by using the technique of transneuronal uptake of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into last order neurones which appears to be activity-dependent. The nerve branches to the spino- and acromio-deltoid muscles were injected with WGA-HRP. Cats preoperatively trained, performed either target-reaching or walking movements. Transneuronally labelled neurones in C2 to C4, located ipsilaterally in laminae V-VIII and contralaterally in lamina VIII, were found in target-reaching cats but not in walking cats. The results show a functional specificity of the C3-C4 PNs and support the proposal of activity dependent transneuronal labelling. It is suggested that this method can be used as a tool for functional identification of last order neurones activated in different movements.

Animals↗
PubMed1988

Sparing of skilled forelimb reaching and corticospinal projections after neonatal motor cortex removal or hemidecortication in the rat: support for the Kennard doctrine.

Skilled forelimb use in reaching for food was studied in rats with variously sized and placed unilateral cortical lesions given in adulthood or on the day of birth. Fluorescent retrograde labelling was used to document changes in corticospinal tracts. In free choice tests, preferential use of the limb ipsilateral to damage was induced by adult motor, but not parietal or occipital, cortex damage. Similar preference for the ipsilateral limb was induced by neonatal motor and parietal, but not occipital, cortex damage. In both adult and neonate groups success with the preferred limb decreased in proportion to the increase in lesion size. To force use of the non-preferred limb, a bracelet, which prevented reaching but not other movements, was attached to the forearm of the preferred forelimb. Success with the non-preferred limb was poorer than with the preferred limb and success again decreased in proportion to the increase in lesion size. Adult and neonatal rats were divided into 4 groups according to the extent of motor cortex damage. Across all lesion sizes the neonatal operates were significantly more successful than the adult operates and their reaching movements appeared more normal. Surprisingly, some rats with large adult motor cortex lesions or hemidecortications were able to reach. Slow-motion video analysis of reaching impairments in both adult and neonate groups showed that limb extension and food grasping were less impaired than limb retraction and adduction of the limb to the mouth. The results show that the integrity of a neocortical hemisphere is not essential for contralateral limb use in reaching, but contributes to successful use of the limb. Following neonatal lesions, facilitation may be promoted by the ipsilateral neocortex through an augmented ipsilateral corticofugal pathway.

Animals↗
PubMed1989

Motor recovery after cross-reinnervation of a forelimb nerve by the phrenic nerve in cats.

Electromyographic (EMG) activities of forelimb muscles and the diaphragm following cross-reinnervation of the elbow flexor nerve by the phrenic nerve sampled simultaneously with cinematographic recording of forelimb movements, in order to examine whether the respiratory nervous system in adult cats is capable of compensation for movement disorders. The right phrenic and musculocutaneous nerves were cut preparatory to cross-union, the proximal stump of the phrenic nerve being joined to the peripheral stump of the musculocutaneous nerve. Reinnervation of the elbow flexor muscles (m. biceps brachii and m. brachialis) was confirmed in terminal experiments by observing muscular contractions induced by nerve stimulations and/or retrogradely labeled motoneurons in cervical (C5-C7) segments following treatment for horseradish peroxidase (HRP) which had been injected previously into the m. biceps brachii of both sides. Behavioral observations were made in the chronically cross-reinnervated cats. Bipolar EMG recording electrodes were implanted chronically in the right m. biceps brachii, m. triceps brachii and in the left intact diaphragm. In freely moving cats 3-22 months after cross-union surgery, EMG activities in the elbow flexor usually were synchronized with those of the left diaphragm. However, occasionally, in cats cross-reinnervated more than 6 months previously, EMG activities in the right biceps muscle were dissociated from those of the left diaphragm during voluntary movements. During walking, EMG activities in the cross-reinnervated biceps muscle were not coordinated with the walking cycle. By contrast, during voluntary goal directed movements, the cats were capable of reaching their right forepaws to the target in a smooth manner using elbow flexion that was associated with EMG activity of the biceps muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Neuronal activity in normal and deafferented forelimb somatosensory cortex of the awake cat.

Three hundred and seventy-three neurons were recorded from the forelimb representation in the primary somatosensory cortex of unanesthetized, quietly resting adult cats. Of these, 177 were studied from 2 days to 3 weeks after transection of the radial, median and ulnar nerves. Following deafferentation the proportion of cells without receptive fields increased from 24 to 82%, however, the average rate of spontaneous activity did not change nor did the probability of encountering a neuron with a receptive field as a function of depth. Receptive field sizes increased dramatically following deafferentation and the response changed from a reliable short-latency, brisk discharge to one that did not occur on every stimulus. After deafferentation the edges of the receptive field often could not be defined accurately. Spontaneous activity in 31% (n = 47) of the neurons from deprived cortex could be modulated by manipulations of the body but these changes were sufficiently slow and ill-defined that they were not classified as a receptive field. In some cases, manipulation of the body gradually reduced the discharge rate. This slow decline in activity was different from the abrupt inhibition of spontaneous activity elicited by somatic stimuli in another class of cells (n = 18). In other cases the manipulation produced a gradual increase in the discharge rate. After deafferentation antidromically identified corticothalamic and pyramidal tract neurons did not display behaviors different from their counterparts in normal cortex. However, the mean latency for synaptic activation from the ventroposterior thalamus increased from 2.7 ms to 4.6 ms. The lost forelimb receptive fields were rarely replaced by inputs from adjacent body parts over the two-week duration of this study. Most responses to somatic stimuli obtained from cortical neurons in the deafferented cortex were clearly abnormal.

Afferent Pathways↗
PubMed1985

Cellular behavior in the anteroposterior axis of the regenerating forelimb of the axolotl, Ambystoma mexicanum.

Cellular behavior along the anteroposterior axis of the regenerating axolotl forelimb was studied by use of triploid (3N) tissue grafted into diploid (2N) hosts and three-dimensional computer reconstructions. Asymmetrical upper forelimbs were surgically constructed with one half (anterior or posterior) 3N and the other half 2N. Limbs were amputated immediately after grafting or were permitted to heal for 5 or 30 days prior to amputation. When regenerates had attained the stage of digital outgrowth, the limbs were harvested and sectioned in the transverse axis for histological analysis. When all limbs bearing anterior grafts were considered as a group, 77% of the 3N mesodermal cells were observed in the anterior side of the regenerates and 23% were located in the posterior side of the regenerates. When all limbs bearing posterior grafts were considered as a group, 76% of the 3N mesodermal cells were found in the posterior side of the regenerate and 24% had crossed into the anterior side. Healing times of 0, 5, or 30 days prior to amputation had no effect on the experimental outcome. Three-dimensional computer reconstructions revealed that most 3N cells of mesodermal origin underwent short-distance migration from anterior to posterior or from posterior to anterior and intermixed with diploid mesodermal cells near the midpoint of the regenerated anteroposterior axis. Some 3N cells were observed at greater distances from the graft-host interface. By contrast, labeled epidermal cells from both anterior and posterior grafts exhibited long-distance migration across all surfaces of regenerated limbs. Details of a computer-assisted reconstructive method for studying the three-dimensional distribution of labeled cells in tissues are presented.

Ambystoma mexicanum↗
PubMed1983

Cortical KCl reinstates forelimb placing following damage to the internal capsule.

Following unilateral damage to the internal capsule, rats failed to use the contralateral forelimb during tests of contact, chin, and visual placing reactions. Infusion of potassium chloride onto the sensorimotor cortex contralateral to the lesion reinstated placing in the impaired limb and abolished placing in the normal limb. As the drug dissipated, placing in the impaired limb gradually deteriorated, while placing in the normal limb returned. In contrast, potassium chloride applied to the ipsilateral cortex did not reinstate placing. These findings suggest that the loss of forelimb placing following lesions of the internal capsule is due, at least in part, to tonic inhibition from the cortex contralateral to the lesion.

Animals↗
PubMed1991

The "staircase test": a measure of independent forelimb reaching and grasping abilities in rats.

A novel reaching test for the rat has been developed to assess the independent use of forelimbs in skilled reaching and grasping tasks. The apparatus is a plexiglas box with a removable baited double staircase. Food pellets are placed on the staircase and presented bilaterally at 7 graded stages of reaching difficulty to provide objective measures of side bias, maximum forelimb extension and grasping skill. In the present experiment, the apparatus was used to assess the reaching performance of rats following unilateral lesions of the sensorimotor cortex, unilateral lesions of the posterior cortex or bilateral lesions of the olfactory bulbs. The task has the advantage of objective over rating measurement, and the simplicity of the apparatus permits many animals to be tested concurrently.

Animals↗
PubMed1990

Regionally selective roles of the rat's striatum in modality-specific discrimination learning and forelimb reaching.

Rats with ibotenate lesions of either the medial striatum or the lateral striatum were trained in a forelimb reaching task and in acquisition, retention and reversal of either turn (left-right) discrimination or brightness (black-white) discrimination in a cross-shape maze. Compared with the controls, the rats with lesions of the medial striatum showed a reliable, modality-selective impairment in reversal of turn discrimination, but no significant impairment of reaching. In contrast, the rats with lateral striatal lesions showed a significant impairment of forelimb reaching, but not of reversal of either discriminations. Neither medial nor lateral lesions significantly affected acquisition and retention of both discriminations. The findings indicate a predominant role of the medial striatum in monitoring of directional responses, confirm the regionally specific role of the lateral striatum in reaching, and are interpreted to support the hypothesis of parallel motor and cognitive forebrain circuits comprising distinctive regions of the striatum.

Animals↗
PubMed1993

Proximal and distal impairments in rat forelimb use in reaching follow unilateral pyramidal tract lesions.

Although it was once thought that the corticospinal (pyramidal) tract was the main substrate of voluntary movement, the extent to which it is involved in the control of proximal vs. distal musculature, independent finger movements, and movements characteristic of different species of animals now is unclear. The objective of this study was to examine the effects of pyramidal tract lesions on skilled forelimb use in rats. In addition, cell morphology in motor cortex following lesions was examined. Naive and trained rats received unilateral pyramidal sections just rostral to the pyramidal decussation. Performance was assessed and filmed on two reaching tasks. Measures of reaching consisted of success in obtaining food, kinematic analysis of limb trajectory and velocity, and qualitative evaluation of 10 movement components comprising a reach. Pyramidal tract lesions only impaired reaching for single food pellets. Almost all movements comprising a reach, except digit opening, were impaired, including lifting, aiming, pronating and supinating the limb, and releasing food. Although success in limb use was unchanged over the 180 day observation period, there were significant improvements in the qualitative features of limb use. Histologically, the morphology of pyramidal cells in the forelimb area ipsilateral to the lesion seemed normal. Rats with additional damage to adjacent structures, such as the medial lemniscus and olivary complex, were much more severely impaired on the reaching tasks, and displayed similar impairments as judged by qualitative and kinematic measures. The results demonstrate that a number of movements involved in independent limb use are chronically impaired by pyramidal tract lesions in the rat. Nevertheless, significant use of the limb is possible, due perhaps to both the contribution of extrapyramidal motor systems and the influence of the remaining pyramidal system through its extrapyramidal connections. The results not only show that the rat pyramidal tract supports functions very similar to those of primates and thus might provide a good model for some aspects of pyramidal tract dysfunctions, but also they argue that the pyramidal tract is involved in both proximal and distal limb movements.

Animals↗
PubMed1991

Endothelin-mediated constriction of prenodal lymphatic vessels in the canine forelimb.

Endothelin is a 21 amino acid peptide which is produced by the vascular endothelium and is believed to be the mediator of endothelium-dependent vasoconstriction. In the current study we assessed the ability of synthetic human endothelin-1 to affect prenodal lymphatic vessel contractility in the canine forelimb. Intralymphatic infusion of endothelin at 1.09 x 10(-9), 1.09 x 10(-8) and 1.09 x 10(-7) M significantly constricted lymphatic vessels as evidenced by dose-dependent increases in lymphatic perfusion pressure. The increase in lymphatic perfusion pressure seen during intralymphatic infusion of endothelin at 1.09 x 10(-8) M during the intra-arterial infusion of phentolamine was not significantly different from that seen prior to phentolamine, indicating that endothelin-mediated lymphatic constriction is not alpha-receptor mediated. Intra-arterial infusion of endothelin at three infusion rates significantly increased forelimb arterial, systemic and lymphatic perfusion pressures. The constriction seen when endothelin (1.09 x 10(-8) M) was infused intralymphatically in the intact lymphatic system was not significantly different from that observed when only the prenodal lymph vessel was perfused. This indicated that the lymph nodes and efferent lymph vessels do not contribute significantly to the lymphatic constriction produced by endothelin. These data are consistent with the hypothesis that endothelin may modulate lymphatic function under either normal or pathophysiological conditions.

Animals↗
PubMed1986

The inhibitory feedback pathway from the forelimb to C3-C4 propriospinal neurones investigated with natural stimulation.

Light mechanical stimulation of the skin and passive joint movements in the forelimb gave effective activation of interneurones located medially in the C3-C4 segments. Such interneurones may be inhibitory to C3-C4 propriospinal neurones (PNs) and recording from PNs revealed that the stimuli which activated the interneurones evoked inhibition in the PNs. It is postulated that a movement commanded via the C3-C4 PNs evoke impulses in forelimb afferents which by negative feedback control transmission in the C3-C4 PNs and thus govern the execution of the movements.

Afferent Pathways↗
PubMed1986

Effects of dorsal column transection in the upper cervical segments on visually guided forelimb movements.

Complete transection of the dorsal column in C2 in cat gave severe defects in forelimb target-reaching and food-taking tested with retrieval of food from a cylinder. Among the symptoms were marked dysmetria in all directions and dyscoordination of movements in different joints, with only slow recovery over weeks and months. It is postulated that normal visual guidance of forelimb movements to a stationary target depends on somatosensory information to the brain via the dorsal column.

Afferent Pathways↗
PubMed1989

The effect of low pyramidal lesions on forelimb movements in the cat.

Complete transection of the pyramid just rostral to the crossing gave defects in forelimb target-reaching and food-taking tested with retrieval of food from a cylinder. The most marked symptoms were dysmetria, dyscoordination of movement and almost total loss of the food-taking movement. Gradual recovery occurred, but even after 3-4 months the food-taking movement was deficient. The symptoms were less severe than those previously found after a high pyramidotomy but much more pronounced than those observed after complete transection of the corticospinal tract in the spinal cord. The motor defects after a low pyramidotomy closely resemble those found after a high dorsal column transection. It is tentatively proposed that the motor defects after low pyramidotomy are largely due to transection of corticocuneate fibers which regulate the feedback pathway from forelimb afferents to the motor cortex.

Animals↗
PubMed1990

Disinhibition in the monkey prefrontal cortex, by injecting bicuculline, induces forelimb movements learned in a GO/NO-GO task.

Local injection of a GABA (gamma-aminobutyric acid) antagonist, bicuculline, into Brodmann's area 8 (Walker's areas 8A and 45) of the monkey prefrontal cortex induced movements of the contralateral forelimb in 4 monkeys that were well-trained to perform a two-choice visual discrimination GO/NO-GO task by appropriate release of the hand from a lever. But the same procedures of injection in two naive monkeys did not. These results indicate that, during learning of the task, a new structure responsible for learned movement of the forelimb was made in area 8 and was disinhibited by bicuculline and, furthermore, they suggest that inhibitory GABA neurons suppress tonically efferent neurons associated with the initiation of movement.

Animals↗