Functional analysis of spontaneous movements in preterm infants

Spontaneous movements of premature infants between 25 and 34 weeks conceptional age were observed for 1 hr on two or three occasions. Subjects had low-risk prognoses and were clinically stable at the time of testing. Behavioral acts were scored using a 0/1 time sampling technique in 60 continuous, 1-min time blocks. Temporal associations between individual movements were found using chi-square analyses. Some associated behaviors contained combinations consistent with neonatal action patterns, for example, single and bilateral leg kicking, head turning, and mouthing. Features of state organization were also evident in that general motor activity (GM), which has been used as a marker of active sleep (AS) in neonates, was found to cluster temporally with startle, facial, and head movements but not eye movements. Behavioral quiescence (≥5 s) was dissociated from AS-related behaviors (GM, facial, head, and eye movements). Combinations of state-segregated behaviors were more likely to exhibit co-occurrence within 1-min intervals in infant 30 weeks conceptional age and older.     

Kinematic and dynamic synergies of human precision-grip movements

We analyzed the adaptability of human thumb and index finger movement kinematics and dynamics to variations of precision grip aperture and movement velocity. Six subjects performed precision grip opening and closing movements under different conditions of movement velocity and movement aperture (thumb and index finger tip-to-tip distance). Angular motion of the thumb and index finger joints was recorded with a CyberGlove and a three-dimensional biomechanical model was used for solving the inverse dynamics problem during precision grip movements, i.e., for calculating joint torques from experimentally obtained angular variations. The time-varying joint angles and joint torques were analyzed by principal-component analysis to quantify the contributions of individual joints in kinematic and dynamic synergies. At the level of movement kinematics, we found subject-specific angular contributions. However, the adaptation to large aperture, achieved by an increase of the relative contribution of the proximal joints, was subject-invariant. At the level of movement dynamics, the adaptation of thumb-index finger movements to task constraints was similar among all subjects and required the linear scaling of joint torques, the synchronization of joint torques under high velocity conditions, and a flexible redistribution of joint torques between the proximal joint of the thumb and that of the index finger. This work represents one of the first attempts at calculating the joint torques during human precision-grip movements and indicates that the dynamic synergies seem to be remarkably simple compared with the synergies found for movement kinematics.     

Development of spontaneous leg movements in infants with and without periventricular leukomalacia

The main question asked in the present study was whether support could be found for the notion that supraspinal influences on the generation of spontaneous kicking movements become increasingly apparent in the first half-year after birth. In comparing groups of infants with and without damage in tracts connected with the cortex surrounding the central sulcus, such support would consist of the finding that similar patterns of spontaneous kicking are observed early in development, whereas differences between groups should occur with increasing age. Using 3-D registrations, the spontaneous kicking movements of 19 infants with differing degrees of periventricular, lobar, and subcortical leukomalacia based on white matter (WM) abnormalities on ultrasound were compared to those of 10 healthy control infants at 6, 12, 18, and 26 weeks of corrected age. Magnetic resonance imaging recordings were used to identify the location and severity of the brain lesions. Infants with extensive lesions in the periventricular and lobar WM with or without diffuse lesions in the subcortical WM showed a decreased variability on some spatial and temporal parameters of kicks. More importantly, these infants showed a different developmental course for intralimb couplings when compared to the other infants; they were unable to dissociate tight intralimb couplings at 18 and 26 weeks. As all of these infants had substantial damage of the corticospinal tracts, these findings suggest that these tracts are involved in the regulation of intralimb joint dissociations between 4 and 6 months of age. However, caution is needed as areas outside those in which the corticospinal tracts are located could be damaged as well and most of the infants with moderate to severe lesions in the corticospinal tract had additional psychomotor problems. For interlimb couplings and most of the spatial and temporal parameters of kicks, no differences were found between groups. This strengthens the claim that inter- and intralimb couplings are organized in fundamentally different ways.     

Two kinematic synergies in voluntary whole-body movements during standing

We used a particular computational approach, the uncontrolled manifold hypothesis, to investigate joint angle covariation patterns during whole-body actions performed by standing persons. We hypothesized that two kinematic synergies accounted for the leg/trunk joint covariation across cycles during a rhythmic whole-body motion to stabilize two performance variables, the trunk orientation in the external space and the horizontal position of the center of mass (COM). Subjects stood on a force plate and performed whole-body rhythmic movements for 45 s under visual feedback on one of the four variables, the position of the center of pressure or the angle in one of the three joints (ankle, knee, or hip). The Fitts-like paradigm was used with two target amplitudes and six indices of difficulty (ID) for each of the four variables. This was done to explore the robustness of kinematic postural synergies. A speed-accuracy trade-off was observed in all feedback conditions such that the movement time scaled with ID and the scaling differed between the two movement amplitudes. Principal-component (PC) analysis showed the existence of a single PC in the joint space that accounted for over 95% of the joint angle variance. Analysis within the uncontrolled manifold hypothesis has shown that data distributions in the joint angle space were compatible with stabilization of both trunk orientation and COM location. We conclude that trunk orientation and the COM location are stabilized by co-varied changes of the major joint angles during whole-body movements. Despite the strong effects of movement amplitude and ID on performance, the structure of the joint variance showed only minor dependence on these task parameters. The two kinematic synergies (co-varied changes in the joint angles that stabilized the COM location and trunk orientation) have proven to be robust over a variety of tasks.     

Unraveling the interaction between pathological upper limb synergies and compensatory trunk movements during reach-to-grasp after stroke: a cross-sectional study

The aim of the present study was to identify how pathological limb synergies between shoulder and elbow movements interact with compensatory trunk movements during a functional movement with the paretic upper limb after stroke. 3D kinematic joint and trunk angles were measured during a reach-to-grasp movement in 46 patients with stroke and 12 healthy individuals. We used principal component analyses (PCA) to identify components representing linear relations between the degrees of freedom of the upper limb and trunk across patients with stroke and healthy participants. Using multivariate logistic regression analysis, we investigated whether component scores were related to the presence or absence of basic limb synergies as indicated by the arm section of the Fugl-Meyer motor assessment (FMA). Four and three principal components were extracted in patients with stroke and healthy individuals, respectively. Visual inspection revealed that the contribution of joint and trunk angles to each component differed substantially between groups. The presence of the flexion synergy (Shoulder Abduction and Elbow Flexion) was reflected by component 1, whereas the compensatory role of trunk movements for lack of shoulder and elbow movements was reflected by components 2 and 3 respectively. The presence or absence of basic limb synergies as determined by means of the FMA was significantly related to components 2 (p = 0.014) and 3 (p = 0.003) in patients with stroke. These significant relations indicate that PCA is a useful tool to identify clinically meaningful interactions between compensatory trunk movements and pathological synergies in the elbow and shoulder during reach-to-grasp after stroke.     

Sensory feedback alters spontaneous limb movements in newborn rats: Effects of unilateral forelimb weighting

Perinatal mammals show spontaneous movements that often appear random and uncoordinated. Here, we examined if spontaneous limb movements are responsive to a proprioceptive manipulation by applying a weight unilaterally to a forelimb of postnatal day 0 (P0; day of birth) and P1 rats. Weights were calibrated to approximate 0%, 25%, 50%, or 100% of the average mass of a forelimb, and were attached at the wrist. P0 and P1 pups showed different levels of activity during the period of limb weighting, in response to weight removal, and during the period after weighting. Pups exposed to 50% and 100% weights showed proportionately more activity in the nonweighted forelimb during the period of weighting, suggesting a threshold for evoking proprioceptive changes. Findings suggest that newborn rats use movement‐related feedback to modulate spontaneous motor activity, and corroborate studies of human infants that have suggested a role for proprioception during early motor development. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 323–333, 2013     

Postural synergies in axial movements: short and long-term adaptation

Summary Fast backward trunk movements are accompanied by hip, knee and ankle rotation which compensate for the backward shift of the center of gravity. The electromyographic pattern associated with the performance of these movements and the associated synergies consists of a fairly synchronous activation of the prime mover (erectores spinae) and the muscles situated at the back of the leg (hamstring, calf muscles). This pattern is called the non anticipated pattern. The effect of training on the EMG pattern and on the subjects' mechanical performances was investigated by comparing a population of untrained subjects with one of highly trained gymnasts. A new EMG pattern was observed in the highly trained gymnasts, the distally anticipated pattern consisting of an early activation of the gastrocnemius, and in some subjects also of the hamstring, indicating that a long term adaptation had taken place. Performances expressed as a ratio between the displacement of the center of gravity projection onto the ground and the velocity of the movement were clearly better in the gymnasts. Short term adaptation was found to occur in the gymnasts and not in the untrained group when the movement was performed while standing on a narrow support. A suppression of the distal gastrocnemius burst occurred in the gymnasts from the first trial under the constrained standing condition whereas no change occurred in the untrained group. The flexibility of the EMG patterns associated with axial movements occurring either spontaneously or as a result of long or short term training is discussed.     

Interlimb coordination in rhythmic leg movements: spontaneous and training-induced manifestations in human infants

Different rhythmic leg movements in vertebrates can share coordinating neural circuitry. These movements are often similar kinematically, and smooth transitions between the different movements are common. We focused on interlimb coordination of the legs in young infants to determine whether weight bearing and non–weight bearing movements might share coordinating circuitry. If interlimb coordination is controlled by the same circuitry, the same coordination (i.e., either synchronous or alternate) should be seen in different rhythmic movements. Moreover, if we altered the interlimb coordination in one movement through exercise, it should translate to a change in coordination in another rhythmic movement that received no exercise. Video and electrogoniometry were recorded while 46 infants (age, 6.2 ± 1.4 mo) performed non–weight bearing and weight bearing movements. Interlimb coordination was quantified by the phase lag between the movement cycles of each leg. Most infants (83%) showed the same coordination in weight bearing and non–weight bearing movements. Ten infants practiced the form of coordination they did not exhibit in the first visit, in weight bearing for 4 wk. Following practice, 8 of 10 infants changed their interlimb coordination in weight bearing to that practiced. Some who practiced synchronous coordination also changed their coordination in non–weight bearing activity. More infants showed both forms of coordination after practice and smooth transitions between the two forms. The results suggest that interlimb coordination is malleable in infants, and there is a partial sharing of the neural substrates for interlimb coordination between different rhythmic leg movements in infants.     

Increasing selectivity of interlimb coordination during spontaneous movements in 2- to 4-month-old infants

In the field of motor development, a question exists whether spontaneous activity in early infancy serves as a precursor to later-emerging goal-directed behaviors. To answer this question, it is necessary to investigate in detail the properties of spontaneous movements in individual infants. In the current study, we longitudinally examined the spontaneous movements of the end points of the limbs in 6 infants aged 2–4 months. Examinations were carried out every week by using a motion analysis system, and the number of recordings performed for each infant varied from 6 to 9 times. Our major finding was that there was an age-related increase in the velocity and position correlation between arms and between legs, whereas there was no significant change in the velocity, duration, and amplitude of movements of individual limbs. That is, the pattern of spontaneous movements changes from a general activity involving all the limbs to an activity involving more selective interlimb coordination from 2 to 4 months of age. These findings suggest that the dissociated movements of a selective combination of arms or legs during spontaneous movements may be a precursor to functionally dissociated movements during goal-directed behaviors.     

Periodic limb movements and sleep apnoea

This study investigated the relationship of Periodic Leg Movements (PLMs) to the severity of Obstructive Sleep Apnoea (OSA) in 52 patients. In addition the prevalence of PLMs in OSA was compared with two other patient populations: narcolepsy and idiopathic PLM disorder (n = 38). All patients were between 20 and 50 years in age and were compared with a control group of 88 asymptotic paid volunteers aged between 20 and 50. PLMs were scored when tibialis anterior EMG activity lasted 0.5-5.0 s with an amplitude of at least half that of pre-sleep voluntary ankle dorsiflexion and when they were part of 4 or more consecutive events separated by 20-90 s. The prevalence of PLMs in OSA was 27.6%, which was similar to the prevalence in our normal controls of 20.5%. However, in the OSA group the majority of the PLMs occurred in the mild OSA patients (40.7%). This was similar to the prevalence of PLMs in narcoleptics (50%). The prevalence of PLMs in moderate OSA, was 24.5%; similar to that of normal controls. In severe OSA, PLMs were also low (12.5%). There is an inverse relationship between PLMs and the severity of OSA. The greater number of arousals and awakenings associated with respiratory irregularities seen in the severe OSA group produced an equivocal manifestation of PLMs.     

Characterisation of human limb movements by accelerometry

The paper discusses the use of accelerometry as an alternative to electromyography or subjective judgement in the assessment of functional disability. The apparatus described is an accelerometer with an f.m.-f.m. telemetry transmitter, coupled to an f.m. receiver, signal conditioner, subcarrier demodulator and twin integrator to generate positional information from acceleartion. The capabilities and limitations of accelerometry are discussed, typical recordings are presented, and interpretation of recordings is described. It is concluded that the method is well worth pursuing.     

Loading the limb during rhythmic leg movements lengthens the duration of both flexion and extension in human infants

Sensory input is critical for adapting motor outputs to meet environmental conditions. A ubiquitous force on all terrestrial animals is gravity. It is possible that when performing rhythmic movements, animals respond to load-related feedback in the same way by prolonging the muscle activity resisting the load. We hypothesized that for rhythmic leg movements, the period (extension or flexion) experiencing the higher load will be longer and vary more strongly with cycle period. Six rhythmic movements were studied in human infants (aged 3-10 mo), each providing different degrees of load-related feedback to the legs during flexion and extension of the limb. Kicking in supine provided similar loads (inertial) during flexion and extension. Stepping on a treadmill, kicking in supine against a foot-plate, and kicking in sitting loaded the legs during extension more than flexion, whereas air-stepping and air-stepping with ankle weights did the opposite. Video, electrogoniometry, surface electromyography, and contact forces were recorded. We showed that load-related feedback could make either the duration of flexion or extension longer. Within the tasks of stepping and kicking against a plate, infants who exerted lower forces showed shorter extensor durations than those who exerted higher forces. Because older babies tend to step with greater force, we wished to rule out the contribution of age. Eight babies (>8 mo old) were studied during stepping, in which we manipulated the amount of weight-bearing. The same effect of load was seen. Hence, the degree of loading directly affects the duration of extension in an incremental way.     

Interpersonal coordination between breathing and limb movements

This study examined the stability and variability of interpersonal coordination, in which one person breathed while the other moved a wrist back and forth with an inverted pendulum in hand. Nine pairs of subjects coordinated each other's movement in two relative phase modes. In one mode, Radial flexion-Inspiration and Ulnar flexion-Expiration (RIUE), one subject radially flexed the wrist as the other inhaled and ulnarly flexed it as the other exhaled. In the other, Ulnar flexion-Inspiration and Radial flexion-Expiration (UIRE) mode, the wrist was ulnarly flexed at inhalation, and radially flexed at exhalation. Results were as follows: (1) The two were more highly coordinated in RIUE mode than UIRE mode as the frequency of oscillation increased. (2) Phase transitions were observed from URIE to RIUE mode, as the frequency of oscillation increased. And (3) the more different in preferred frequency the pendulum and breathing movements were, the more deviated from the intended relative phase the coordination became. These results suggest that interpersonal coordination of breathing and wrist-pendulum movement is qualitatively equivalent to intra personal coordination between them.     

Estrogen therapy reduces nocturnal periodic limb movements

It is believed that periodic limb movement (PLM) and more specifically, restless leg syndrome (RLS), are a common cause of insomnia. And one study in the literature examined PLM when associated to the use of estrogens. Polo-Kantola et al. [Polo-Kantola P, Rauhala E, Erkkola R, Irjala K, Polo O. Estrogen replacement therapy and nocturnal periodic limb movements: a randomized controlled trial. Obstet Gynecol 2001;97(4):548-54] observed that estrogen therapy improved subjective sleep quality regardless of periodic limb movements or related arousals. Herein is a case of a symptomatic postmenopausal patient with high PLM index who complained of insomnia and leg pain. Given that the patient had hot flashes and a high Kupperman Menopausal Index (which evaluates climacteric symptoms), we decided to administer transdermal ESTRADOT 25 microg (Novartis, Brazil) twice-a-week. Our patient experienced a significant decrease in PLM as well as a great increase in REM and a slight increase in slow wave sleep (stages 3 and 4), as shown in the polysomnography. The patient reported an overall improvement in her condition.     

Oscillatory cortical changes during periodic limb movements

STUDY OBJECTIVES: Periodic limb movements are a distinctive and frequent finding on polysomnography. The pathophysiology and clinical significance of these common sleep-related movements are not yet well understood. The brainstem, spinal cord, and peripheral nervous system may be implicated in the pathogenesis of periodic limb movements. The goal of our study was to probe if there is any participation of cortical mechanisms in the periodic limb movements. We focused the study on the analysis of electroencephalogram oscillations around the periodic limb movement. PARTICIPANTS: We selected polysomnographic recordings of 6 patients diagnosed with periodic limb movements of sleep. METHODS/DESIGN: We analyzed the cortical activity offline after averaging 10-second segments, having the middle point with the beginning of each limb movement in non-rapid eye movement sleep, selecting exclusively samples without obvious arousals. In each patient, polysomnographic segments containing limb movements were selected from both slow-wave (stage 3-4) and lighter (stage 1-2) non-rapid eye movement sleep. RESULTS: An increase in all the frequencies immediately after the limb movements, having the maximum 2.5 to 3 seconds after the beginning of the movement, was found. The slope started 1.5 to 2 seconds before the limb movements. The topography of this activity was different from the activity accompanying voluntary movements in the awake state. The meaning of this activity is uncertain, but one possibility is its relationship with microarousals or an increase of the sensory inputs. The beginning of the increase before the limb movements suggests that the cortex may be engaged during the neural changes associated with this kind of movement, though not playing a causal role.     

Motion quality evaluation of upper limb target-reaching movements

Fitts' Law was extended in the polar coordinate system, and a set of indices for human motion evaluation is proposed. In this paper, the index of difficulty and the index of performance are introduced as the general indices for the quality measure of plane target-to-target movement. As an example, the target-reaching movement of the upper limb, which is a basic functional action of upper limbs in the activities of daily living, was experimentally investigated. Five healthy subjects were asked to perform six target-reaching tasks with different indices of difficulty. All movements were recorded using a Vicon motion analysis system. The movement quality was measured using these evaluation indices.     

Biokinetical analysis of hind limb movements of the dog

Summary This study of movements of the hind limb of the dog was performed with the aid of cinephotography and electromyography. The weight of the limb segments and their centers of gravity were determined. From these data the forces operating at the centers of the limb segments during a cycle of a stride have been calculated and their influence on the joints have been analysed.From this study is concluded: 1) muscular activity is present when the effect of external forces must be overcome and subsides when these external forces act positively in the direction of the progression; 2) gravity and ground-reaction play an important role in the propulsion of the body, especially when there is no activity in the important retractors of the limb at the end of the support phase; 3) moments about the stifle and tarsal joints are opposite at the end of support phase and swing phase; 4) activity of the flexor digitorum superficialis (and also of the gastrocnemius muscles) during the support phase and of the peroneus longus muscle during the swing phase contribute to the coordination of the movements and to the stabilization of these joints.     

Posturally induced transitions in rhythmic multijoint limb movements

The coordination dynamics (e.g., stability, loss of stability, switching) of multijoint arm movements are studied as a function of forearm rotation. Rhythmical coordination of flexion and extension of the right elbow and wrist was examined under the following conditions: (1) forearm supine (forearm angle 0°), simultaneous coordination of wrist flexion/elbow flexion and wrist extension/elbow extension (termed in-phase); and (2) forearm prone (forearm angle 160°), simultaneous coordination of wrist flexion/elbow extension and wrist extension/elbow flexion (termed anti-phase). Starting in either pattern, subjects rotated the forearm in nine 20° steps, producing 15 cycles of motion per step at a frequency of 1.25 Hz. Spontaneous transitions from pattern 1 to pattern 2 and from pattern 2 to pattern 1 were observed at a critical forearm angle. The critical angle depended on the direction of forearm rotational change, thus revealing the hysteretic nature of the switching process. En route to the transition, regardless of direction of forearm rotation, enhancement of phase fluctuations and an increase in perturbation response times (critical slowing down) were observed in the relative phasing between the joints. Such observations support loss of stability as a central, self-organizing process underlying coordinative change. Neurophysiological mechanisms supporting multijoint coordinative dynamics are discussed.     

Motor control of aimed limb movements in an insect

Limb movements that are aimed toward tactile stimuli of the body provide a powerful paradigm with which to study the transformation of motor activity into context-dependent action. We relate the activity of excitatory motor neurons of the locust femoro-tibial joint to the consequent kinematics of hind leg movements made during aimed scratching. There is posture-dependence of motor neuron activity, which is stronger in large amplitude (putative fast) than in small (putative slow and intermediate) motor neurons. We relate this posture dependency to biomechanical aspects of the musculo-skeletal system and explain the occurrence of passive tibial movements that occur in the absence of agonistic motor activity. There is little recorded co-activation of antagonistic tibial extensor and flexor motor neurons, and there is differential recruitment of proximal and distal flexor motor neurons. Large-amplitude motor neurons are often recruited soon after a switch in joint movement direction. Motor bursts containing large-amplitude spikes exhibit high spike rates of small-amplitude motor neurons. The fast extensor tibiae neuron, when recruited, exhibits a pattern of activity quite different to that seen during kicking, jumping, or righting: there is no co-activation of flexor motor neurons and no full tibial flexion. Changes in femoro-tibial joint angle and angular velocity are most strongly dependent on variations in the number of motor neuron spikes and the duration of motor bursts rather than on firing frequency. Our data demonstrate how aimed scratching movements result from interactions between biomechanical features of the musculo-skeletal system and patterns of motor neuron recruitment.