Neural Control of Interappendage Phase During Locomotion

Interappendage phasing of crayfish swimmeret movements dependsupon a central nervous system network of command, oscillator,and coordinating neurons. The command neurons serve to set thegeneral excitation level in each of the segmental oscillators.The oscillator neurons in each hemi-ganglion generate the rhythmicalternations of powerstroke and returnstroke motor neuron activity.The coordinating neurons transmit the precise timing informationabout the state of one oscillator to other oscillators. Thisinformation can serve to advance or to delay the motor burstsdriven by the other oscillators. Which effect is observed dependsupon the arrival time of the coordinating neuron discharge withinthe cycle period of the modulated oscillator. This type of modulationleads to the prediction that a stable interappendage phase canresult from situations where there is not a fixed excitabilitygradient among the segmental oscillators. This prediction hasbeen verified using a cut command neuron preparation.     

Control of the Cranio-Cervical System During Feeding in Birds

The avian neck is a complex, kinematically redundant system,which plays a role during inter alia food prehension and manipulation.Kinematical analysis shows that chickens (Gallus domesticus)move their vertebrae according to a geometric principle thatmaximizes angular rotation efficiency. The movement patternshows simultaneous rotations in some joints, while not in theothers. Anseriformes show a pattern of successive, rather thansimultaneous rotations in the rostral part of the neck. A kinematicalmodel indicates that the geometric principle produces an anseriform-likepattern only if a constraint on the movement of the caudal vertebraeis introduced. The strength of this constraint, required fora realistic simulation, is related to the amount of stretchin the long dorsal neck muscles (M. biventer and M. longus collidorsalis), which have a different configuration in Anseriformescompared to the chicken. To investigate whether the differencein movement pattern is a result of differences in anatomy only,or also of differences in neuromotor patterns, the EMG-patternsof the neck muscles of the mallard and chicken during drinkingand pecking were studied. Considerable overlap in the activityof antagonists is found in mallards, but not in chickens. Musclesin the rostral part of the neck are activated successively inmallards, but simultaneously in chickens. We conclude that thedifference in movement patterning between chickens and Anseriformes,results from both a difference in the control system of theneck, and a difference in the anatomy. The anseriform patternis found in water as well as on land, which suggests that neckmovement in both environments is controlled by the same neuromotorpatterns. The modifications in motor control system and anatomyof the Anseriformes may have evolved as an adaptation to aquaticfeeding, since the anseriform pattern is energetically morebeneficial in an aquatic environment than on land.     

Interlimb Coordination During Locomotion

SYNOPSIS. Studies of interlimb control during cat locomotionare directed at four different levels of organization. Interlimbstepping patterns are described from studies of the timing ofelectromyographic activity of muscles of different limbs. Patternsof coordination are based on the frequency of occurrence ofthe phasing of step cycles of the different limbs. Selectivespinal cord lesions are used to perturb those patterns of coordinationand have implicated two ascending spinal systems in interlimbcontrol: long ascending propriospinal neurons (LAPNs) and neuronsof the ventral spinocerebellar tract (VSCT). The results ofneuroanatomical tract tracing experiments indicate that twodifferent populations of LAPNs exist which might provide directconnection between cervical and lumbosacral locomotor centersbut that neurons of the VSCT do not make such connections. Theseresults imply that the role of the VSCT in interlimb controlis by way of the cerebellum. Unit recordings made from axonsof the VSCT during treadmill locomotion are consistent withthe VSCT carrying information about the timing of both hindlimbstep cycles.     

鸟类后肢骨骼组合的长度比例及其机理初步分析

鸟类后肢骨骼是组成鸟类运动系统的主要部分,也是协助鸟类完成各项功能行为的骨骼组成.不同生态类型的鸟类在后肢骨骼的组成上存在明显的特征,并以此相区别.本文通过大量对比分析不同类型、不同生态系统鸟类后肢骨骼的组成特点初步认为:鸟类后肢骨骼的长度组成及比率特征是与其运动栖息习性等机能紧密联系的.习于地面行走、奔跑为特征的典型地栖鸟类,后肢骨骼中胫跗骨最长,其次跗跖骨长度大于股骨;而以树上栖息、跳跃为特征的典型树栖鸟类,后肢骨骼中胫跗骨最长,而股骨长度大于跗跖骨;猛禽类因生活习性介于前两类鸟类之间,故股骨与跗跖骨长度比较也是在二者之间变化的.同时应用三元图表方法得出的直观统计结果也同样说明上述结论,并尝试对不同鸟类后肢骨骼的运动机能进行推断.本研究从系统解剖学角度将鸟类后肢骨骼系统与运动功能进行对比剖析,同时对于了解、解释鸟类的运动机理也具有直接的意义,而且依此结论也可作为恢复古鸟后肢骨骼长度和判断其生态行为的参考依据.     

Locomotion and Posture During Terminal Branch Feeding

We investigated locomotor and postural behavior during terminal branch feeding in order to gain a better understanding of the motor capabilities of primates. We videotaped wild, juvenile bonnet macaques (Macaca radiata) in India as they fed on flower nectar in a simal tree (Bombax malabaricum). Kinematic analysis revealed that they select specific support surfaces and movements that, for their body design and postures, maximize lateral stability and minimize the chances of falling. These choices are made even though the distance and duration of travel to a selected target are frequently increased. Our discussion focuses on particular concepts of how primates contend with balance problems arboreally, potential reasons for changes in footfall patterns, and how the tail contributes to arboreal locomotion and posture. We concluded that balance problems due to the ratio of body size to branch size are usually avoided, at least among juvenile bonnet macaques, by placing the hands and feet on branches extending laterally from the central support branch and not on the central branch itself. The lateral branches permit a wide base of support, which increases lateral stability. Second, juvenile bonnet macaques have a striking ability to rapidly and repeatedly adapt their gait patterns to changing substrate design with minimal interruption to overall progression. Third, primate tails that are not morphologically specialized for prehension nevertheless have important prehensile and sensory functions in arboreal locomotion and posture.     

The Control of Color in Birds

SYNOPSIS. The colors of birds result from deposition of pigments—mainlymelanins and carotenoids—in integumentary structures,chiefly the feathers. The plumages of birds indicate their age,sex, and mode of living, and play important roles in camouflage,mating, and establishment of territories. Since feathers aredead structures, change of color of feathers is effected throughdivestment (molt) and replacement. The color and pattern ofa feather are determined by the interplay of genetic and hormonalinfluences prevailing in its base during regeneration. Mostbirds replace their feathers at least once annually. Some wearthe same kind of basic plumage all the time butothers alternatea basic and breeding plumage, either in one (the male) or bothsexes. Still others may have more than two molts, adding supplementalplumage at certain times in the plumage cycle. The varietiesof patterns of molt, the kinds of plumage, and the colors andpatterns of feathers among birds apparently are the result ofseveral kinds of selection pressures working through evolution.     

Temperature Effects on Locomotion and Activity Bioenergetics of Amphibians, Reptiles, and Birds

1) Large temperature differences have a measurable effect onectothermic power consumption both at rest and during locomotion,yet this question remains to be satisfactorily addressed inecological studies looking at optimal foraging strategy andperformance. 2) Acclimation may influence the enzyme complementpresent in ectotherms and this could influence the energeticcost and efficiency of locomotion for ectotherms. 3) There maybe an optimal temperature for ectothermic locomotion and thismay vary from species to species, yet we measure power consumptionduring locomotion uniformly at 30°C. 4) Endothermic locomotionas demonstrated by birds is temperature sensitive, as was shownby Paladino and King (1984). Although the locomotory cost maynot change, thermoregulatory adaptations allow the bird to usethe heat produced during locomotion in the cold to reduce thermoregulatorypower requirements. 5) Avian hypothermia and inactivity is nota last ditch effort to save energy, but a strategy that allowsendotherms to conserve energy reserves during inactivity orstressful environmental conditions.     

The Evolution of the Functional Role of Trunk Muscles During Locomotion in Adult Amphibians

SYNOPSIS. The axial musculature of all vertebrates consistsof two principal masses, the epaxial and hypaxial muscles. Theprimitive function of both axial muscle masses is to generatelateral bending of the trunk during swimming, as is seen inmost fishes. Within amphibians we see multiple functional andmorphological elaborations of the axial musculature. These elaborationsappear to be associated not only with movement into terrestrialhabits (salamanders), but also with subsequent locomotor specializationsof two of the three major extant amphibian clades (frogs andcaecilians). Salamanders use both epaxial and hypaxial musclesto produce lateral bending during swimming and terrestrial,quadrupedal locomotion. However during terrestrial locomotionthe hypaxial muscles are thought to perform an added function,resisting long-axis torsion of the trunk. Relative to salamanders,frogs have elaborate epaxial muscles, which function to bothstabilize and extend the iliosacral and coccygeosacral joints.These actions are important in the effective use of the hindlimbsduring terrestrial saltation and swimming. In contrast, caecilianshave relatively elaborate hypaxial musculature that is linkedto a helix of connective tissue embedded in the skin. The helixand associated hypaxial muscles form a hydrostatic skeletonaround the viscera that is continuously used to maintain bodyposture and also contributes to forward force production duringburrowing.     

Bioelectric Control of Locomotion in the Ciliates*†

SYNOPSIS. Locomotor behavior in the ciliate protozoa is controlled by the cell membrane through electrophysiological principles already familiar in receptor, nerve, and effector cells of the metazoa. This is illustrated by the avoiding reaction (15). When the membrane of the anterior part of the ciliate receives a mechanical stimulus, as during collision, it permits a local influx of Ca⁺⁺. This constitutes a receptor current which depolarizes the remaining cell membrane by electrotonic spread. Depolarization causes a secondary transient increase in the calcium conductance of the entire cell membrane, and a general influx of Ca⁺⁺ occurs. The resulting increase in concentration of intracellular Ca⁺⁺ activates a reorientation (“reversal”) of the ciliary power stroke, causing the organism to swim backward. Forward locomotion is restored as the resting concentration of intracellular Ca⁺⁺ in the cell cortex is restored by diffusion, active extrusion, or intracellular sequestering. The control and coordination of locomotion in ciliates depend on several factors in addition to the excitable properties of the membrane. These include the sensitivities of the ciliary apparatus to intracellular concentrations of calcium and other regulating substances, the anatomical distribution of sensory receptor properties of the cell membrane, and the cable properties of the cell which permit electrotonic spread of graded potential signals without need of all-or-none conducted signals.     

Molecular and Genetic Analysis of Unc-7, a Caenorhabditis Elegans Gene Required for Coordinated Locomotion

Mutations in the Caenorhabditis elegans gene unc-7 confer an uncoordinated phenotype. Wild-type animals trace smooth, sinuous waves as they move; unc-7 mutants make irregular bends or kinks along their bodies, particularly when they move forward. The unc-7 locus has also been implicated in the nematode's response to volatile anesthetics. We have cloned unc-7 by transposon tagging: an unc-7 mutation was correlated with the insertion of the transposon Tc1, and reversion of the mutant phenotype was correlated with loss of the Tc1 element. We have physically mapped the region flanking the sites of Tc1 insertion and identified DNA rearrangements corresponding to eight additional unc-7 alleles. Northern analysis indicates that a 2.7-kb unc-7 message is present in all developmental stages but is most abundant in L1-L3 larvae. The 5' end of the message contains a trans-spliced leader SL1. An 18-kb intron is located upstream of the predicted translational start site of the gene, and DNA breakpoints of four gamma-ray-induced alleles were located within this intron. We determined the sequence of a cDNA corresponding to the unc-7 message. The message may encode a 60-kd protein whose amino acid sequence is unrelated to any other available protein sequence; a transmembrane location for the unc-7 protein is predicted. We predict from our analysis of unc-7 genetic mosaics that the unc-7 gene product is not required in muscle cells for wild-type coordination but is probably required in motor neurons (although a hypodermal role has not been excluded). We speculate that unc-7 may be involved in the function of neuronal ion channels.     

Control of Locomotion In Vitro: II. Chemical Stimulation

Previous studies have described the presence of alternating activity induced in left and right ventral roots of the neonate rat in vitro brainstem-spinal cord preparation, following application of certain neuroactive substances to the bathing solution. The present findings show the presence of chemically induced, adult-like coordinated airstepping demonstrated by electromyographic recordings in the hindlimb-attached in vitro brainstem-spinal cord preparation. Analysis of muscular activity demonstrated alternation between antagonists of one limb and between agonists of different limbs, as well as a proximodistal delay in agonists active at different joints of the same limb. Neuroactive agents were applied independently to either the brainstem or spinal cord bath. The substances surveyed in the present studies included some of those used previously, as well as additional compounds: bicuculline and picrotoxin (γ-aminobutyric acid-ergic antagonists), N-methyl-D-aspartic acid (excitatory amino acid agonist), substance P, acetylcholine, carbachol (cholinergic agonist), and serotonin. Application of these substances to the brainstem bath produced rhythmic airstepping. Application of dopamine, aspartate, glutamate, and N-methyl-D-aspartic acid to the spinal cord bath also produced rhythmic airstepping, while application of acetylcholine produced tonic, long-lasting co-contractions. These findings reveal the presence of several neurochemical systems in the central nervous system that can be activated at birth to induce coordinated airstepping in the neonate rat in vitro brainstem-spinal cord preparation.     

Locomotion in caterpillars

Most species of caterpillar move around by inching or crawling. Their ability to navigate in branching three‐dimensional structures makes them particularly interesting biomechanical subjects. The mechanism of inching has not been investigated in detail, but crawling is now well understood from studies on caterpillar neural activity, dynamics and structural mechanics. Early papers describe caterpillar crawling as legged peristalsis, but recent work suggests that caterpillars use a tension‐based mechanism that helps them to exploit arboreal niches. Caterpillars are not obligate hydrostats but instead use their strong grip to the substrate to transmit forces, in effect using their environment as a skeleton. In addition, the gut which accounts for a substantial part of the caterpillar's weight, moves independently of the body wall during locomotion and may contribute to crawling dynamics. Work‐loop analysis of caterpillar muscles shows that they are likely to act both as actuators and energy dissipaters during crawling. Because caterpillar tissues are pseudo‐elastic, and locomotion involves large body deformations, moving is energetically inefficient. Possession of a soft body benefits caterpillars by allowing them to grow quickly and to access remote food sources safely.     

Single Muscle Surface EMGs Locomotion Identification Module for Prosthesis Control

Neurophysiology - Surface EMG (sEMG) signals along with pattern recognition algorithms demonstrate a significant potential to identify and predict human motor activity. We propose a single-channel...