Motor Output Patterns Research Articles

Toward a Movement Dynamics Perspective on Dual-Task Performance

The effect of practice on the parallel organization and control of discrete, asymmetrical bimanual movements was investigated. Subjects performed a flexion movement in the left limb together with a flexion-extension-flexion movement in the right limb. Two groups, one of which received kinematic information feedback, were instructed to produce the different patterns simultaneously. A third group performed each movement in isolation at all times, serving as the baseline condition. The degree of success in parallel action organization was assessed at the qualitative (or structural) and quantitative (or metrical) level of movement specification. Findings revealed that the bimanual groups displayed a tendency to synchronize the patterns of motor output, resulting in (mutual) interference. However,the provision of augmented kinematic information feedback resulted in more successful metrical and structural dissociation of the limb actions. The results are discussed in support of a movement dynamics perspective on motoric dual-task performance. The relevance of the approach for human factors is also emphasized.

Control of asymmetrical bimanual movements

When movements are performed together in the upper-limbs, a strong tendency emerges to synchronize the patterns of motor output. This is most apparent when trying to do different things at the same time. The present experiment explored the simultaneous organization and control of spatiotemporally different movements. There were two practice conditions: symmetrical and asymmetrical. In the symmetrical condition, subjects performed a series of unidirectional elbow flexion movements, followed by a series of elbow flexion-extension-flexion (reversal) movements in both limbs simultaneously. In the asymmetrical practice condition, subjects performed the unidirectional movement in the left limb together with the reversal movement in the right limb. Findings revealed a tendency for each limb movement to assimilate the features of its counterpart under the latter condition. This effect was "asymmetrical" in that the unidirectional movement was more attracted to the reversal movement than vice versa. Nevertheless, subjects were able to partly suppress this synchronization tendency as was evident from the moderate cross correlations between the angular acceleration patterns of both limb movements and from an increasingly successful differentiation of the activity levels in the right and left limb muscles. All together, these findings provide evidence for some degree of parallel control of spatiotemporally different actions. The data are discussed in view of the possible suppression of a bilaterally distributed motor control system, that is mainly held responsible for activiting proximal limb musculature.

Influence of speaking rate on the upper lip, lower lip, and jaw peak velocity sequencing during bilabial closing movements

Upper lip, lower lip, and jaw movements were recorded in five adult speakers for repeated sequences of the utterance [bae] at different speech rates. The results failed to confirm several earlier reports of an invariant upper lip, lower lip, jaw peak velocity sequencing pattern for bilabial closures. While the earlier reported sequence was the most frequent, a wide variety of different sequences was also commonly observed. In addition, significant intersubject differences in sequencing were found. The present results thus do not support the earlier hypothesis that oral closure gestures reflect aspects of a centrally generated pattern of motor output during speech.

Effect of putative neuromodulators on rhythmic buccal motor output in Lymnaea stagnalis

The effects of a variety of neuromodulator substances on rhythmic motor output and activity in neurons in the feeding circuitry of Lymnaea stagnalis were examined. Each neuromodulator produced a unique combination of effects at different levels in the network: i.e., pattern-generating interneurons (N1, N2, and N3), an identified higher-order interneuron (cerebral giant cell, CGC), and buccal motoneurons. 5-Hydroxytryptamine, acetylcholine, and FMRFamide all inhibited rhythmic motor activity. However, this was achieved in different ways. Dopamine changed the nature of rhythmic activity from one in which N2 interneuronal activity was predominant ("N2 rhythm") to a feeding rhythm. Dopamine was the only substance capable of activating the feeding rhythm. Activity in the CGC was increased by 5-hydroxytryptamine, dopamine, and acetylcholine and reduced by FMRFamide. Differential responses in buccal motoneurons were also observed. The results are discussed in relation to previous work on other species and also in terms of the selection of different patterns of motor output by neuromodulators.

Nonspiking interneurons in the ventilatory central pattern generator of the shore crab, Carcinus maenas.

Eight nonspiking interneurons were identified that are elements of the central pattern generator controlling ventilation in the shore crab, Carcinus maenas. Intracellular recordings from these neurons in an isolated ganglion preparation revealed that these cells exhibit large amplitude oscillations in their membrane potentials, which are in-phase with the ventilatory motor pattern. These oscillations are present during the expression of the two distinct ventilatory motor output patterns corresponding to forward and reversed ventilation, and the oscillations stopped during pauses in the ventilatory rhythm. Injection of intracellular current pulses into these interneurons caused a resetting of the ongoing ventilatory rhythm, indicating that these cells are part of the ventilatory central pattern generator. The structure of each interneuron was determined by the intracellular injection of Lucifer Yellow dye. These neurons have a large diameter main neurite ranging from 10 to 20 microns in diameter with very restricted primary and secondary branching from the main neurite. All of the interneurons are restricted to a single hemiganglion and perturbation of these cells with intracellular current pulses only affect the motor output of the hemiganglion containing the interneuron. These eight nonspiking interneurons appear to be the primary components of the central pattern generator underlying ventilation in the crab.

1988 Volvo award in biomechanics. The triaxial coupling of torque generation of trunk muscles during isometric exertions and the effect of fatiguing isoinertial movements on the motor output and movement patterns.

Previous studies have shown that reduction of precise motor control accompanies local muscular fatigue. The effects of isodynamic fatiguing of flexion and extension trunk movements on the movement patterns and the motor output of the trunk were investigated. Twenty male subjects with no history of low-back pain for the past 6 months volunteered for the study. A triaxial dynamometer was used that simultaneously provided measurement of torque, angular position and velocity of each axis. Resistances were set independently for each axis by an interfaced computer. The subjects performed trunk flexion and extension movement against a sagittal plane resistance equal to 70% of their maximum isometric extension strength in the upright position. The minimum resistances in the coronal and transverse planes were set up at 7 Newton meters. The subjects were asked to perform trunk movement as quickly and as accurately as possible while exerting the maximum efforts until exhaustion. Analysis of variance, the MANOVA procedure with a repeated measure design, was performed among the selected parameters of the first, middle and last three repetition cycles. The selected parameters are the trunk motor output and movement patterns; the total angular excursion, range of motion, maximum and average torque and angular velocity of the trunk. All the selected parameters were significantly reduced in the sagittal plane. Subjects displayed significantly less motor control and greater range of motion in the coronal and transverse planes in performing the primary task of flexion and extension. The reduction in the functional capacity of the primary muscles performing the required task is compensated by secondary muscle groups and the spinal structure is loaded in a more injury prone pattern, as identified by finite element models. In addition it is suggested that the fatigued muscles would be less able to compensate any perturbation in the load or position of the trunk. The repetitive loading results in a weakening of the viscoelastic passive elements of the spineless structure. The loss of ability to protect these weakened passive elements makes the spine susceptible to industrial and recreational injuries.

Parametric features of inhibition of feeding in Aplysia by associative learning, satiation, and sustained lip stimulation.

In order to determine whether different classes of behavioral plasticity affect common or unique neural loci, the effects of three types of processes that inhibit feeding in Aplysia were quantified. Changes in feeding behavior due to an associative learning task in which animals learn that food is inedible were compared with behavioral effects caused by satiation and by sustained lip stimulation. The data indicate that each process modifying feeding can be characterized by differences in time to stop responding to food, by differences in specificity of the decrement to a particular food, and by different patterns of motor output before complete cessation of responsiveness. The data suggest each process inhibiting feeding acts at a different neural site. Learning that food is inedible may be due to facilitation of a specific sensory pathway onto pattern generators producing rejection responses. Sustained lip stimulation seems to inhibit feeding by causing a decrement in all outputs of a particular sensory pathway. Finally, satiation appears to represent inhibition of feeding motor elements.

Organization of rhythmic buccal motor output of Lymnaea stagnalis in the absence of food

The pond snail Lymnaea stagnalis exhibits spontaneous rasping movements in the absence of food which are thought to be involved in food searching activity. Rasping activity is patterned into bouts, separated by periods of quiescence. Recordings from buccal feeding motoneurons in the isolated CNS reveal similar bouts of rhythmic motor output, though the modal cycle period is significantly longer than that shown by intact snails. Log survivorship curves of interval data from both intact animals and isolated CNS indicate that the pattern of motor output is controlled by at least two processes, one generating intervals between rasps within a bout, and the other generating intervals between bouts of rasping. When compared to well-fed individuals, 2-day-starved snails show significant enhancement of the probability function for generation of intervals between rasps within a bout; the function underlying between-bout intervals is not significantly affected.

In vitro brainstem-spinal cord preparations for study of motor systems for mammalian respiration and locomotion

Recently developed in vitro preparations of the brainstem-spinal cord from neonatal rat suitable for investigation of motor control systems for mammalian locomotion and respiration are described. The preparations remain viable for extended periods under standard in vitro conditions and generate rhythmic motor patterns for locomotion and respiration. The methodology of the preparations and characteristics of the motor output patterns are described. The preparations retain functional circuitry for major components of the motor control systems, including brainstem respiratory and spinal locomotor pattern generating networks, brainstem locomotor command regions, descending bulbospinal and ascending spinal pathways, and mechanosensory afferent input systems. They therefore offer potential for investigation of diverse aspects of the mammalian respiratory and locomotor control systems.

Intersegmental Coordination of Central Neural Oscillators for Rhythmic Movements of the Walking Legs in Crayfish, Pacifastacus Leniusculus

ABSTRACT The neuronal circuits underlying rhythmical movements of the walking legs in crayfish Pacifastacus leniusculus are organized into central oscillators within each thoracic hemiganglion. These segmental networks are coupled in different modes of coordination during activities such as walking and limb waving. This paper examines the nature of the coupling between hemisegmental oscillators in the absence of sensory feedback, and the effect of phasic input from a major limb proprioceptor. In isolated preparations of the thoracic nerve cord, adjacent ipsilateral hemiganglia can generate a rhythmic motor output pattern in which homologous motor roots discharge approximately synchronously (the ‘in-phase’ rhythm). In contrast, contralateral hemiganglia show no evidence of any such phase-locking in their activity. A single proprioceptor at the base of each limb, the thoracic-coxal muscle receptor organ (TCMRO), can influence the timing and intensity of the rhythmic output of two or more ipsilateral thoracic ganglia. Rhythmical stretch-release of the TCMRO of the fourth ganglion on one side can entrain the motor rhythms of both the third and fourth ipsilateral hemiganglia, in the in-phase pattern of coordination. The TCMRO also elicits intra- and intersegmental reflexes during expression of the in-phase motor rhythm. These reflexes are centrally modulated in a phasedependent manner. Thus mechanical stimulation of the TCMRO co-activates homologous sets of motoneurones in adjacent ipsilateral hemiganglia only during their active (spiking) phase in the motor rhythm. We discuss the implications of these results for the generation and coordination of walking and other rhythmic behaviour of the thoracic limbs in decapod Crustacea. Our data shed further light on the properties of the motor rhythm generator for walking in crayfish, and suggest that the concept of a central pattern generator cannot be rigorously applied in this system.

On the definition of central pattern generator and its sensory control

A central pattern generator (CPG) is defined here as a neural network responsible for the production of the timing cues of a rhythmic motor output pattern in the isolated CNS. For the intact animal, model considerations show that this term is neither clearly delimited from the concept of a reflex chain nor from the concept of a pattern generator with functional principles different from those of the CPG. Therefore, it cannot be concluded from the existence of a CPG in the isolated nervous system that this CPG also provides the decisive timing cues in the intact animal. Consequences for the study of the neural basis of rhythmic movements are shown.

反応時間の運動パターン依存性の検討 : その発達的変化と性差について

As children age , motor performance improves . There are many variables discussed in the development literature to which these changes in performance are attributed. Those mentined most frequently are physical growth, biomechanical and physiological factors. Overviews of these factors have been presented elsewhere (cf. Thomas. 1980). Reaction time experiments have often been used to investigate developmental variables affecting the motor output Process (Furui, Seki and Kasai, 1983). In normal subjects, the premotor reaction time (PMT) of the biceps brachii has been determined to be different in flexion (F) and supination (S)of the forearms. Accordingly, because the same muscles performs in both functions and PMTs of those two different movement patterns are definitely different, this would suggest that these two voluntary movements would be separately organized in the brain (Kasai, 1983, 1984). The present experiments are therefore undertaken to examine the developmental changes and sexual differences of these motor output systems by means of those reaction time tasks and collect information with respect to which these changes in performance are attributed. The subjects for the present study are 100 male children (20 subjects from seven to eleven years old, respectively) and 98 female children (20 subjects in each age category, except nine-years old). They were all right-handed. The tasks of the subject were the F and the S of right forearm only, responding to a sound signal as quickly as possible. Mechanical reaction timed (MRTs) of the F and the S were measured with the digitimer. The premotor reaction times (PMTs) of both movement patterns with the surface EMG of the biceps brachii among the nine, ten and eleven years old groups, respectively were also measured. As the regression coefficience of MRT and PMT in the F and the S were extremely significant (Furui, Seki and Kasai, 1983), motor times (MTs) were obtained by subtracting PMTs from MRTs. The main findings in the present study are summarized as follows: 1. MRTs of mrile and female children shortened in both movement patterns as they grew older. Those phenomena were especially noticeable between seven and nine years old. 2. MRTs of the F were always shorter than those of the S. However, MRT differences between two movement patterns disappeared at eleven years old. 3. MRTs of male children in both movement patterns were always shorter than those of female children. Since PMTs of male and female children in both movement patterns were not different, the reason why MRTs were different between both sexes was the differences in MTs (peripheral motor functions). 4. PMTs which mean central motor functions (motor pattern generator) were not different for both sexes among the nine , ten and eleven years o1d group , but this function appeared earlier for the female than for the male. However, this function of the male was superior to that of the female from ten years old. From the present results, two different motor functions (motor output and motor pattern generators) were considered which showed the developmental changes of reaction times in two different movement patterns.

Analysis Of The Scaphognathite Ventilatory Pump in the Shore Crab Carcinus Maenas III. Neuromuscular Mechanisms

ABSTRACT The motor output pattern to one of the ventilatory muscles of the scaphognathite (SC) in the shore crab, Carcinus rnaenas, was analysed from extracellular nerve recordings. During ‘forward mode’ bursting, an increase in the burst rate of L2b motor neurones is accompanied by an increase in the average intraburst firing frequency. The number of action potentials per burst, although variable, does not change consistently as a function of burst rate. The influence of individual aspects of the motor pattern on isotonic contractions of muscle L2b was examined. Increasing the intraburst frequency leads to greater contraction and work output, and allows the muscle to lift heavier loads. This effect is correlated with an increase in the level of postsynaptic depolarization, due, at least in part, to greater summation of EPSPs. Increasing the burst rate alone also enhances muscle contraction and work, and results in greater depolarization. This latter effect appears to involve an accumulation of short-term facilitation, which becomes more acute as the time interval between the bursts is progressively shortened. In addition, contraction and depolarization are augmented by increasing the number of impulses per burst or the number of axons recruited. These observations indicate some aspects of the motor output pattern which are appropriately modified to accommodate the changes in force and work demands which accompany a change in gill ventilation rate.

Neural control of hatching: fate of the pattern generator for the leg movements of hatching in post-hatching chicks

Chicks from 0 to 61 days post-hatching were gently folded into the hatching position and placed in artificial glass eggs. Within 0 to 2 min they began to produce a behavior that qualitatively resembled normal hatching. Furthermore, quantitative analysis of electromyographic records showed that under these conditions the intralimb and interlimb leg motor output patterns produced during each hatching episode (the episode motor program) were those typical of normal hatching. The only major change associated with increasing post-hatching age was a gradual increase in inter-episode interval. Therefore, we conclude that the neural pattern-generating circuitry which produces the motor program for the leg movements of hatching remains functional in post-hatching chicks despite the fact that, under normal conditions, hatching behavior is never used again.

Sustained Responses to Brief Stimuli: Swimming in Xenopus Embryos

ABSTRACT Prolonged responses to brief triggering or releasing stimuli are commonplace in animal behaviour. The initiation of locomotion is an example but hypotheses for the central nervous origin of locomotory rhythms generally do not explain how activity is sustained. After a brief review, which suggests that positive feedback excitation could be involved, evidence fromXenopus embryos is considered. Here a brief skin stimulus can evoke long episodes of swimming even in curarized embryos. Feedback excitation provides a possible explanation for sustaining fictive swimming. This hypothesis is evaluated by simulation of simple neuronal networks using a physiologically realistic digital computer modelling programme. The results from simulations suggest that: (1) positive feedback excitation could sustain activity either in central pattern generators for locomotion or in postural motor systems and (2) that the model networks tested here are not appropriate to produce the pattern of motor output from the Xenopus embryo spinal cord.

Motor Programme Switching in the Ventilatory System of Carcinus Maenas: the Neuronal Basis of Bimodal Scaphognathite Beating

ABSTRACT Intracellular recordings have been made from ventilatory neurones in semi-isolated and isolated thoracic ganglia of the crab Carcinus during spontaneous switching between the two motor programmes underlying forward and reversed beating of the scaphognathites (SGs). Ventilatory reversals are dependent upon the central activation of two subgroups of motoneurones which are normally silent, and different from those driving the same SG muscles during the forward rhythm. Two further subgroups of motoneurones remain active throughout both rhythm modes. The results suggest that both motor output patterns are produced mainly by periodic inhibitory synaptic input from the same oscillator network, and that neural switching between the rhythm modes occurs directly at the level of the motoneurones themselves. It appears that both sets of ‘forward’ and ‘reversal’ motoneurones are driven continuously throughout oscillator activity, and that bursting activity in these sets is gated by the selective application or removal of additional, tonic inhibition.

Selective Recruitment of Interganglionic Interneurones During Different Motor Patterns in Pleurobranchaea

ABSTRACT The buccal and anterior head structures of the mollusc, Pleurobranchaea, participate in several types of behaviour which are generated largely by rhythmic activity produced in the brain and buccal ganglia. This paper examines the neuronal mechanisms (1) by which motor output from these ganglia is coordinated, and, (2) which underlie the generation of different motor patterns. Preliminary experiments indicated that the neuronal circuitry which produces the rhythms is contained in each of the paired buccal ganglia. The timing characteristics of the rhythms arise in the buccal ganglia and the pattern and symmetry of motor output in the brain roots are determined by activity in buccal cerebral interneurones (BCI) within the buccal ganglia. Intracellular recordings showed that unique properties of individual cells within two pools of interganglionic interneurones, the BCI and paracerebral cells (PCC), determine in part the types of coordinated patterns that are produced. The BCI, which project to the brain, are a heterogeneous population of cells, based on : ( 1 ) the activity they evoke when they are depolarized ; and (2) their activity patterns during rhythms that are evoked by buccal nerve stimulation. Evidence is presented to show that BCI are selectively recruited to produce the distinguishing features of different motor patterns. Similarly, the PCC were found to be a diverse group of cells that exert both excitatory and inhibitory effects on the nervous system. Stimulation of excitatory PCC in isolated nervous systems elicited a variety of activity patterns. These data suggest that the PCC may selectively recruit the BCI to produce different motor patterns and that differences in patterns can be attributed, in part, to the unique properties of individual cells within each pool of interneurones.

CHEMO‐ORIENTATION

Summary1. A new classification system for chemo‐orientation mechanisms is suggested, based on delineating (a) internal and external orientation information available to an organism, (b) mode of information processing, (c) type of motor output pattern, and (d) guidance systems that modulate or direct motor output.2. Cross‐phyletic comparison of chemo‐orientation indicates that morphology, to a greater extent than phylogeny, determines the kind of chemo‐orientation mechanisms available to an organism. Analogies are drawn between single‐celled organisms with surface chemical receptor sites and higher organisms with elaborate chemosensory organs and nervous systems.

Interneurones Co-Ordinating the Ventilatory Movements of the Thoracic Spiracles in the Locust

ABSTRACT A pair of interneurones has been identified by intracellular recording and staining which co-ordinates the movements of the thoracic spiracles in the ventilatory rhythm. An interneurone has its cell body on the left or on the right side of the metathoracic ganglion and an axon which ascends to the other thoracic ganglia in the contralateral connective. Each interneurone produces bursts of spikes in time with the inspiratory phase of ventilation. These spikes evoke inhibitory post-synaptic potentials (IPSPs) in thoracic spiracular closer motor neurones. Both interneurones synapse upon the closer motor neurones in each thoracic segment. These connexions, which may be direct, inhibit the spiking of the closer motor neurones during inspiration. The interneurones do not appear to have an innate rhythmicity but instead receive a periodic synaptic input which inhibits their spikes during expiration. The underlying cause of the spikes is less clear. Apart from brief periods at the start and end of a burst, the spikes occur at a constant frequency that is independent of the ventilatory rate. The pattern of the spiracular motor output could be altered by manipulating the frequency and number of spikes in an interneurone. When the frequency of spikes in the interneurone was raised, the motor bursts had a higher initial frequency and were of briefer duration ; when the frequency was lowered, the motor bursts were of lower initial frequency and of longer overall duration. Altering the spikes in one interneurone, however, could not affect the frequency of the ventilatory rhythm, or reset the rhythm.

Experiments on the central pattern generator for swimming in amphibian embryos

The central nervous system of paralysed Xenopus laevis embryos can generate a motor output pattern suitable for swimming locomotion. By recording motor root activity in paralysed embryos with transected nervous systems we have shown that: (a) the spinal cord is capable of swimming pattern generation; (b) swimming pattern generator capability in the hindbrain and spinal cord is distributed; (c) caudal hindbrain is necessary for sustained swimming output after discrete stimulation. By recording similarly from embryos whose central nervous system was divided longitudinally into left and right sides, we have shown that: (a) each side can generate rhythmic motor output with cycle periods like those in swimming; (b) during this activity cycle period increases within an episode, and there is the usual rostrocaudal delay found in swimming; (c) this activity is influenced by sensory stimuli in the same way as swimming activity; (d) normal phase coupling of the left and right sides can be established by the ventral commissure in the spinal cord. We conclude that interactions between the antagonistic (left and right) motor systems are not necessary for swimming rhythm generation and present a model for swimming pattern generation where autonomous rhythm generators on each side of the nervous system drive the motoneurons. Alternation is achieved by reciprocal inhibition, and activity is initiated and maintained by tonic excitation from the hindbrain.