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PubMed1975

Motor-sensory cortex-corticospinal system and developing locomotion and placing in rats.

Normal and abnormal development of movement in the rat were studied by investigating the growth and organization of the motor-sensory cortexcorticospinal tract system (MSC-CST) and the functional and morphologic effects of ablating the MSC or quadrants of it at different ages. Major growth of the MSC outflow, the CST, in the brain stem and rostral cord occurred in the second and third weeks postnatally, coinciding approximately with the normal mid-week transition from infantile to mature locomotion. Ablation of the MSC at birth revealed that while the MSC-CST was not essential for ordinary locomotion on flat terrain, its presence hastened normal development of this kind of movement, and that it was absolutely essential for locomotion on difficult terrain. The MSC quadrants showed quite different, and in some domains mutually exclusive, CST projection patterns to forebrain, diencephalon, brain stem, and spinal destinations (determined by Fink-Heimer-Nauta fiber degeneration studies). Ablation of some quadrants produced distinctive syndromes of disordered movement: the posterolateral quadrant related to active grasping in positioning limbs, while the posteromedial quadrant related to tactile motor-sensory positioning of limbs. Thus in addition to the classic somatotopic organization of the MSC, there was another kind of organization into regions concerned with components of integrated movement of a number of parts of the body. Several forms of aberrant circuitry developed after MSC ablations in infants, but their possible roles in functional adaptation remain to be determined.

Age Factors↗
PubMed1977

Mode of locomotion of Schwann cells migrating in vivo.

The manner of locomotion of Schwann cells during normal development was studied by means of repeated observations and photomicrographs of individual cells at closely spaced time intervals and focal levels. In developing tadpole peripheral nerves, Schwann cells move sporadically with brief periods of rapid translation of the whole cell interspersed with longer intervals when the cell shows little or no overall movement. Highest rates of locomotion averaged 5 micrometer/minute with a duration of no greater than four to six minutes. Net rates of speed measured over at least 20 minutes were always considerably lower, with the average being 1.9 micrometer/minute. Rapid locomotion involves protrusion and growth of several pseudopodia, while the cell body remains in place, followed by attachment of these processes to an axonal surface, and finally detachment of the trailing portions of the cell as the entire cell hitches forward, "inchworm-style".

Animals↗
PubMed2006

Asymmetries in postural control and locomotion in chimpanzees (Pan troglodytes).

Posture and locomotion are two of the most primitive and basic motor manifestations of an organism's behavior. Although the restrictions they impose on other motor functions are evident, few studies have considered the possibility of asymmetries in these behaviors in human and nonhuman primates, and how they might impact other asymmetries at higher functional levels. The aim of the current study was to explore in a group of 10 chimpanzees at the Madrid Zoo-Aquarium the degree of asymmetry in four behaviors related to locomotion (walking, ascending, descending, and brachiating) and four behaviors associated with posture (sitting, lying, hanging, and changing postures). Few subjects showed individual preferences, but significant trends in the group for some of the behaviors were found, including right-hand use when initiating quadruped walking, and left-hand use when descending and hanging. Some significant correlations also emerged: a negative one between walking and descending, and a positive one between walking and brachiating and between sitting and changing postures. No correlations were found between locomotor and postural modes. Although we cannot make generalizations on the population level at this time, these findings highlight the importance of considering postural and locomotion factors when studying motor asymmetries in primates.

Animals↗
PubMed2005

Comparative postcranial body shape and locomotion in Chlorocebus aethiops and Cercopithecus mitis.

Body weight and length, chest girth, and seven postcranial limb segment lengths are compared between two guenon species, Chlorocebus (Cercopithecus) aethiops (vervets) and Cercopithecus mitis (blue monkeys), exhibiting different habitual locomotor preferences. The subjects, all adults, were wild caught for a non-related research project (Turner et al. [1986] Genetic and morphological studies on two species of Kenyan monkeys, C. aethiops and C. mitis. In: Else JG, Lee PC, editors. Primate evolution, proceedings of the Xth International Congress of Primatology, Cambridge. London). The morphological results are interpreted within the context of previously published observations of primate locomotion and social organization. The sample is unique in that the body weight of each individual is known, allowing the effects of body-size scaling to be assessed in interspecific and intersexual comparisons. C. mitis has a significantly (P < 0.05) greater body weight and trunk length than C. aethiops. A shorter trunk may function to reduce spinal flexibility for ground-running in the latter. Proximal limb segments (arm and thigh) are significantly greater in C. mitis, reflecting known adaptations to committed arboreal quadrupedal locomotion. By contrast, relative distal limb segments (forearm, crus, and foot) are significantly longer in C. aethiops, concordant with a locomotor repertoire that includes substantial terrestrial quadrupedalism, in addition to arboreal agility, and also the requisite transition between ground and canopy. Although normally associated with arboreal monkeys, greater relative tail length occurs in the more terrestrial vervets. However, because vervets exploit both arboreal and terrestrial habitats, a longer tail may compensate for diminished balance during arboreal quadrupedalism resulting from the greater "brachial" and "crural" indices that enhance their ground quadrupedalism. Most interspecific differences in body proportions are explicable by differences in locomotor modalities. Some results, however, contradict commonly held "tenets" that relate body size and morphology exclusively to locomotion. Generally associated with terrestriality, sexual dimorphism (male/female) is greater in the more arboreal blue monkeys. A more intense, seasonal mating competition may account for this incongruity.

Animals↗
PubMed2001

Tripedal knuckle-walking: a proposal for the evolution of human locomotion and handedness.

A comparative morphological analysis of human and non-human hominoids was conducted in an attempt to determine the mode of locomotion of the protohominid. Although the generalized hominoid anatomy permits variation of locomotion: brachiation, knuckle-walking, etc., minor variations in structure determine which behavior is favored. Arboreal arm swinging requires a flexible forelimb while terrestrial fist or knuckle-walking demands more rigidity of the hand and wrist. It is demonstrated that the large human thumb accompanied by the strong adduction of the thenar, hypothenar, and palmar interosseous muscles offer powerful rigidity to the hand, while fusion of the os centrale with the scaphoid during gestation permits the formation of an arch of carpals which imbue the wrist with the stability necessary for weight bearing. Fascialization of the contrahentes and dorsiepitrochlearis muscles in the human as well as depilation of the middle phalanges; the webbing (syndactyly) of the palm; the direction of the fibers of the interosseous membrane of the forearm; the shape of the puerile annular ligament, and the direction of the human glenoid fossa strongly suggest that the ancestor of man used a knuckle-walking form of locomotion prior to becoming bipedal. A model is presented that suggests that bipedalism was attained through an intermediate stage of tripedalism. The model is based on the fact that man's anatomy is much more asymmetric than that of the great apes. A presumption is made that due to the absence of trees for climbing in the transition from forest to open plain, the protohominid needed to carry tools (stones) at all times for protection. Stones could be carried for long distances on the posterior iliac crest since the weight would be shifted posteriorly over the legs. Pick up, medial rotation and adduction of the stone would employ a two-muscle chain of biceps brachii and latissimus dorsi. On the iliac crest, the stone is posterior to the coronal plane of the glenohumeral joint, and with the contraction of this two-muscle chain, the shoulder on one side is moved posteriorly effecting a semi-erect posture. It is proposed that tripedalism of the protohominid may be an explanation for the handedness unique to hominids.

Animals↗
PubMed1993

Neural organization of the locomotive oscillator.

We study the relation of neural development, organization, and activity to behavior. We provide a model of the locomotive oscillator, a neural system supplying alternating stimulation to extensor and flexor muscles creating an oscillatory motion. We propose a protocol by which this neural system starting from unstructured, unconnected neural populations develops structure and function. The protocol is studied by both computer simulation and mathematical analysis. Our main results are 1. The locomotive oscillator self-organizes and maintains its organization, assuming certain properties of the neural populations. 2. Imperfections disturbing the functional adequacy of the neural populations may lead to the deterioration and disappearance of the oscillatory behavior. 3. The locomotive oscillator may fail to organize if the development is not staged in time.

Animals↗
PubMed1995

A model of the neuro-musculo-skeletal system for human locomotion. I. Emergence of basic gait.

The generation of human locomotion was examined by linking computational neuroscience with biomechanics from the perspective of nonlinear dynamical theory. We constructed a model of human locomotion, which includes a musculo-skeletal system with 8 segments and 20 muscles, a neural rhythm generator composed of 7 pairs of neural oscillators, and mechanisms for processing and transporting sensory and motor signals. Using a computer simulation, we found that locomotion emerged as a stable limit cycle that was generated by the global entrainment between the musculo-skeletal system, the neural system, and the environment. Moreover, the walking movements of the model could be compared quantitatively with those of experimental studies in humans.

Biomechanical Phenomena↗
PubMed1996

Characteristics of voluntary visual sampling of the environment for safe locomotion over different terrains.

The characteristics of visual sampling required for successful locomotion over various terrains is the focus of this work. In the first experiment we directly address the role of continuous visual monitoring of the environment in guiding locomotion by allowing the subjects to choose when and where to take a visual sample of the terrain and examine the effects of different terrains on characteristics of visual sampling. Young subjects walked over travel paths of varying difficulties while wearing opaque liquid crystal eyeglasses and pressed a hand-held switch to make the glasses transparent when they needed to sample the environment. Travel time and visual sampling characteristics were recorded. Results show that intermittent sampling (less than 50%) of the environment is adequate for safe locomotion, even over a novel travel path. The frequency, duration and timing of visual samples are dependent on terrain characteristics. Visual sampling of the environment is unaffected by preview restriction of the travel path and is increased when specific foot placement is required and there is a potential hazard in the travel path. In the second experiment we dissociated steering control and obstacle avoidance from specific foot placement and examined visual sampling demands prior to the initiation of the swing phase and during the swing phase. The results show that steering control and obstacle avoidance do influence the visual sampling time, which is scaled to the magnitude of change. Vision was used in a feedforward control mode to plan for and initiate appropriate changes in the swing limb trajectory: its use during the swing phase to provide on-line control was minimal.

Adult↗
PubMed1992

A comparison of intact and in-vitro locomotion in an adult amphibian.

Locomotion was compared in an intact and in-vitro preparation of the adult mudpuppy (Necturus maculatus). The intact animals walked on an aquatic treadmill while in-vitro preparations were made to walk with a bath application of the excitatory amino acid NMA (N-methyl DL-aspartate). EMG recordings of shoulder muscles (pectoralis, latissimus dorsi, dorsalis scapulae, and procoracohumeralis) and elbow muscles (brachialis and extensor ulnae) were obtained from intact animals while recordings were made from only the elbow muscles in-vitro. The in-vitro preparation required magnesium in the bath to initiate and maintain locomotion, consistent with an NMDA mediated response. Also consistent with an NMDA response was the finding that glycine potentiated the NMA induced locomotion in-vitro. The range of cycle durations seen in-vitro was well within the range seen in the intact animal, while gait analysis demonstrated the similarity of intact and in-vitro locomotor cycles. In spite of these very similar locomotor patterns there are interesting differences in the patterned output seen in-vitro, such as the absence of a second burst in the brachialis muscle in-vitro.

Animals↗
PubMed1996

Disynaptic vestibulospinal and reticulospinal excitation in cat lumbosacral motoneurons: modulation during fictive locomotion.

This study compares some characteristics of the disynaptic excitatory pathways from the lateral vestibular nucleus (LVN) and medial longitudinal fasciculus (MLF) to lumbosacral alpha-motoneurons in the decerebrate cat. We used the spatial facilitation technique to test whether disynaptic LVN and MLF excitatory postsynaptic potentials (EPSPs) are produced by common last-order interneurons in the lumbosacral segments of the spinal cord. Of 77 motoneurons examined, 26 exhibited disynaptic EPSPs from both supraspinal sources. No spatial facilitation was found between LVN and MLF EPSPs in 21 of 24 cells that were adequately tested. In 3 of 23 cells (all flexor motoneurons), some spatial facilitation was found in some but not all trials. These observations suggest that stimulation of the LVN and MLF produces disynaptic EPSPs in motoneurons through largely separate populations of last-order interneurons. Disynaptic MLF and LVN EPSPs showed parallel patterns of modulation during fictive locomotion. Maximal disynaptic EPSP amplitudes occurred during the phase of the step cycle when the recorded motoneuron, whether flexor or extensor, exhibited depolarizing locomotor drive potentials and the corresponding muscle nerve was active. These observations, taken together, suggest that disynaptic LVN and MLF EPSPs are produced in motoneurons by at least four separate populations of segmental last-order excitatory interneurons, with separate populations projecting to flexor versus extensor cells. The results also suggest that the modulation of the disynaptic EPSPs during fictive locomotion is mainly due to premotoneuronal convergence of input from the respective descending systems and from the segmental central pattern generator for locomotion onto common interneurons.

Animals↗
PubMed1987

The role of Renshaw cells in locomotion: antagonism of their excitation from motor axon collaterals with intravenous mecamylamine.

The contribution of Renshaw cell (RC) activity to the production of fictive locomotion in the mesencephalic preparation was examined using the nicotinic antagonist mecamylamine (MEC). After the i.v. administration of 3 doses of MEC (1.0 mg/kg) the following observations were made: 1) ventral root (VR) evoked discharge of RCs was decreased by up to 87.7%, 2) recurrent inhibitory postsynaptic potentials recorded in alpha motoneurons were greatly reduced or abolished, and 3) the rhythmic firing of RCs during the fictive step cycle was abolished in 83% of the cells examined. Locomotor drive potentials (LDPs) in motoneurons persisted during the fictive step cycle after MEC administration. Bursts of motoneuron firing during each fictive step cycle were characterized by increased frequency and number of spikes after MEC, although the burst duration was unaltered for similar step cycle lengths. A greater number and frequency of spikes per burst was also observed in Ia inhibitory interneurons (IaINs), which remained rhythmically active after MEC administration. It is concluded that Renshaw cells are not an integral part of the spinal central pattern generator for locomotion, nor do they control the timing of the motoneuron or IaIN bursts of firing during fictive locomotion. The data are consistent with a role for RCs in limiting the firing rates of motoneurons and IaINs during each burst.

Animals↗
PubMed1988

Phasic modulation of short latency cutaneous excitation in flexor digitorum longus motoneurons during fictive locomotion.

We examined modulation of transmission of short-latency excitation produced by distal hindlimb cutaneous input, as well as fluctuations in motoneuron membrane potential and input resistance, in flexor digitorum longus (FDL) motoneurons during fictive locomotion. Fictive stepping was induced in unaesthetized, decerebrate cats either by repetitive stimulation of the mesencephalic locomotor region (MLR) or by administration of Nialamide and 1-DOPA after low spinal section. In the MLR preparations, brief depolarizing waves occurred in FDL cells during the early flexion phase of fictive stepping, immediately after cessation of activity in extensor muscles. In some FDL cells, plateau-like depolarizations also occurred during the extensor phase. Fictive stepping induced in acutely spinalized cats by administration of 1-DOPA was slower and more variable; peak polarization in FDL motoneurons always occurred during the early flexion phase but there was usually no distinct depolarization during extension. In both types of preparation, the initial EPSP components in synaptic potentials (SP-EPSPs) produced by electrical stimulation of the cutaneous division of the superficial peroneal nerve (SP) were maximally facilitated during early flexion, coincident with the peak of background depolarization. This enhancement was manifested by an increase in the amplitude of initial SP-EPSP components or by decreased central latency of the initial EPSP components, or both. In most FDL motoneurons, input resistance decreased systematically during late flexion, coincident with relative membrane hyperpolarization. Correction of SP-EPSP amplitudes for changes in input resistance suggested that SP-EPSP facilitation persisted throughout the flexion phase. These findings are discussed with reference to modulation of cutaneous reflexes during locomotion and the possibility that excitatory last-order interneurons in particular cutaneous reflex pathways may distribute excitatory drive from the central pattern generator for locomotion to FDL alpha-motoneurons.

Action Potentials↗
PubMed1984

Alcohol increases both locomotion and immobility in mice: an ethological analysis of spontaneous motor activity.

The effects of alcohol on locomotor activity of group- and individually-housed mice were studied using direct ethological observations, including a detailed postural analysis and measures of both locomotion and immobility. Ethanol (0, 0.5, 1.0 and 2.0 g/kg, IP) was given to subjects placed alone in a novel cage, and videotape recordings of behaviour were made. Locomotor activity was unchanged or increased by alcohol administration. Immobility was profoundly increased, however, at both the intermediate and high doses of alcohol, so that there was a simultaneous increase in measures of both locomotion and immobility. These increases were possible because of a decrease in certain active but non-locomotor elements of behaviour, such as rearing and digging. There generally appeared to be little effect of differential housing, although blood alcohol levels were significantly higher in group-housed animals. This depressant effect of alcohol would probably not be detected by simply recording locomotor activity, since ambulation itself was unchanged or increased. Measurements of both locomotion and immobility may thus more accurately detect stimulant and depressant effects of drugs.

Animals↗
PubMed2002

Effect of MS-153 on the development of behavioral sensitization to locomotion- and ataxia-inducing effects of phencyclidine.

RATIONALE: Repeated administration of phencyclidine (PCP) produces behavioral sensitization to PCP. Although the precise mechanism is unknown, glutamatergic neurotransmission seems to play an important role in the development of sensitization. OBJECTIVES: The present study examined whether a novel compound, MS-153 (( R)-(-)-5-methyl-1-nicotinyl-2-pyrazoline), which has an ability to enhance glutamate uptake and inhibit glutamate release, would block the development of behavioral sensitization to PCP. METHODS: For studying effects of MS-153, locomotor activity was measured by an infrared sensor and ataxia was measured by a rating scale. RESULTS: MS-153 (10 and 100 mg/kg) enhanced locomotion and ataxia induced by a single injection of PCP (7.5 mg/kg). Repeated administration of PCP (20 mg/kg, once in every day, for 5 days) developed sensitization to locomotion- and ataxia-inducing effects of PCP (7.5 mg/kg). MS-153 given 60 min and 120 min later of every PCP treatment blocked the development of behavioral sensitization to both locomotion- and ataxia-inducing effects of PCP. Co-administration of MS-153 with repeated saline treatment did not produce hypersensitivity to PCP. CONCLUSIONS: These results suggest that the attenuation of glutamatergic neural transmission enhances acute effects of PCP, in contrast, blocks the behavioral sensitization developed by repeated PCP treatment. Therefore, glutamatergic neural transmission plays an important role in the development of behavioral sensitization to PCP.

Animals↗
PubMed2002

Lesions of extrastriate cortex and consequences for visual guidance during locomotion.

One of the functions of the putative motion pathway in visual cortex may be visual guidance during locomotion. Using cats, we have investigated the role of the first area in this pathway, the lateral suprasylvian visual area (LS, often considered analogous to the primate area MT). Visual function during locomotion was tested by looking at the accuracy of foot placement as cats walked down a cluttered alley. Cats were tested before and after LS was lesioned bilaterally using ibotenic acid. In all four cats tested, partial lesions of LS caused a significant deterioration in the accuracy of foot placement, though cats showed no deficit in acuity or in pattern discrimination. To determine whether the observed deficit was specific to the motion pathway, in two additional cats lesions were made in the central field representation in area 19, which lies adjacent to LS but belongs to the putative object recognition pathway. Surprisingly, both cats showed significant improvements in their accuracy of foot placement during locomotion. The reason for this improvement was unclear.

Animals↗
PubMed2002

Effects of cholinergic and noradrenergic agents on locomotion in the mudpuppy (Necturus maculatus).

Some neurotransmitters act consistently on the central pattern generator (CPG) for locomotion in a wide range of vertebrates. In contrast, acetylcholine (ACh) and noradrenaline (NA) have various effects on locomotion in different preparations. The roles of ACh and NA have not been studied in amphibian walking, so we examined their effects in an isolated spinal cord preparation of the mudpuppy ( Necturus maculatus). This preparation contains a CPG that produces locomotor activity when N-methyl- D-aspartic acid (NMDA), an excitatory amino acid agonist, is added to the bath. The addition of carbachol, a long acting ACh agonist, to the bath disrupted the walking rhythm induced by NMDA, while not changing the level of activity in flexor and extensor motoneurons. Adding clonidine, an alpha(2)-noradrenergic agonist, had no effect on the NMDA-induced walking rhythm. Physostigmine, an ACh-esterase inhibitor, disrupted the walking rhythm, presumably by potentiating the effects of endogenously released ACh. Atropine, an ACh antagonist that binds to muscarinic ACh receptors, blocked the effects of carbachol, indicating that the action is mediated, at least in part, by muscarinic receptors. In the absence of carbachol, atropine had no effect. Locomotion was not induced by carbachol, atropine or clonidine in a resting spinal cord preparation. Cholinergic actions do not seem to be essential to the CPG for walking in the mudpuppy, but ACh may convert a rhythmic walking state to a more tonic state with occasional bursts of EMG activity for postural adjustments.

Acetylcholine↗
PubMed2003

The allocation of attention during locomotion is altered by anxiety.

We tested the hypotheses that: (1) anxiety regarding the possibility of falling alters the attentional demands of gait; and (2) this alteration in the attentional requirements of gait occurs independently of gait pattern accommodations. Sixteen younger and 15 older adults participated in this study. Subjects walked at a self-determined velocity along a 7.2-m walkway under four conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (60 cm vs 15 cm) and the height of the walking surface (0 cm vs 60 cm). Attentional demands of locomotion in each condition of testing were assessed using the dual-task methodology, in which participants verbally responded to an auditory cue as quickly as possible while continuing to walk. Our findings revealed that: (1) participants were successful in verbally responding to the auditory cue without modifying their gait pattern; (2) reaction times increased for all subjects when walking in the condition of greatest postural threat; (3) the attentional demands for locomotion varied with the phase of the gait cycle for younger adults but not for older adults; (4) the phase-dependent effect for younger adults disappeared in the condition of greatest postural threat, while reaction time scores for older adults systematically increased; and (5) increases in reaction time persisted despite significant changes in gait kinematics. Our findings confirm that anxiety increases the attentional demands for locomotion and provide further explanation for age-dependent increases in the attentional demands of gait. Furthermore, our findings confirm that fall-related anxiety predicates an increase in the allocation of attention to locomotor control that is independent of gait pattern adjustments.

Adult↗
PubMed2005

Dynamic visual-vestibular integration during goal directed human locomotion.

Normal visual input plays a very dominant role during locomotion. Functionally, it can assist the central nervous system to overcome a destabilizing effect of abnormal or perturbed vestibular information. However, a recent study has shown a directional effect of transmastoidal galvanic vestibular stimulation (GVS) on gait trajectory when visual information is unreliable. The purpose of this study was to investigate how inputs from the visual and vestibular systems are weighted to optimize locomotor performance under impoverished visual conditions during goal directed locomotion. For unimodal stimulation, the visual input was manipulated using displacing prisms that caused 14 degrees horizontal displacement of perceived target location to the right or left. In addition, GVS (0.8 mAmp) was applied to manipulate vestibular system information during bimodal stimulation conditions. Two bimodal stimulation conditions were defined by the polarity of the galvanic current (anode on congruent and incongruent sides of prismatic deviation). The center of mass (CoM) displacement, head and trunk yaw angles and trunk roll angles were computed to analyze the global output as well as segmental coordination, as the participants walked towards the target. Although the performance was primarily guided by visual information, both congruent and incongruent GVS significantly altered CoM displacement. Similarly, the basic pattern of segmental responses during steering was maintained; however, the magnitude of the responses was altered. Spatio-temporal analysis demonstrated that during bimodal stimulation, the effect of GVS on global output tapered off as the participants approached the target. Results suggest a dynamic visual-vestibular interaction in which the gain of the vestibular input is initially upregulated in the presence of insufficient or impoverished visual information. However, there is a gradual habituation and the visual information, although insufficient, primarily dominates during goal directed locomotion. The experimental trajectories resembled mathematically simulated trajectories with a decaying GVS gain as opposed to a constant gain, further supporting the dynamic nature of sensory integration.

Adult↗