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Biomedical subjects

J Massion

Publications and source records attributed to J Massion.

At least 19 recordsLinked to original sources
PubMed1995

Preparatory postural adjustments in parkinsonian patients with postural instability.

BACKGROUND: Postural instability is a common problem in patients with Parkinson's disease. This paper reports results of a study undertaken to investigate some of the possible mechanisms responsible for this instability. METHODS: Preparatory postural adjustments associated with a lateral leg raising task were studied in five parkinsonian patients and four age-matched controls. Recordings included ground reaction forces, kinematics, and surface EMG activity from multiple leg muscles. RESULTS: In normal subjects there was a well-defined sequence of events preceding the onset of leg elevation, beginning with a transfer of centre of foot pressure (CP), initially toward the moving leg and then back to the support side, followed by displacement of the trunk toward the support side. In the more severely affected parkinsonian patients, the amplitude of the initial displacement of CP was markedly reduced. The interval between the earliest force changes and the onset of leg elevation was prolonged and the relative timing of the kenematic adjustments during this interval was disrupted. In addition the alternating burst and periods of inhibition observed in the EMG recordings from the normal subjects were replaced by continuous tonic EMG activity. CONCLUSIONS: These observations suggest that abnormalities in programming preparatory postural adjustments may contribute to postural instability in some patients with advanced Parkinson's disease.

Aged↗
PubMed1994

Postural control system.

The postural control system has two main functions: first, to build up posture against gravity and ensure that balance is maintained; and second, to fix the orientation and position of the segments that serve as a reference frame for perception and action with respect to the external world. This dual function of postural control is based on four components: reference values, such as orientation of body segments and position of the center of gravity (an internal representation of the body or postural body scheme); multisensory inputs regulating orientation and stabilization of body segments; and flexible postural reactions or anticipations for balance recovery after disturbance, or postural stabilization during voluntary movement. The recent data related to the organization of this system will be discussed in normal subjects (during ontogenesis), the elderly and in patients with relevant deficits.

Age Factors↗
PubMed1994

[Quantitative approach of postural asynergia in cerebellar diseases].

In his original description of cerebellar asynergia, Babinski, in 1899, presented a patient with cerebellar dysfunction performing a backward upper trunk bending. When the patient tried to bend his head and trunk, his lower limbs stayed almost motionless, because the associated flexion of the knee and hip, usually observed in a normal subject, did not take place. To reassess the possibility that asynergia may actually be a symptom of cerebellar dysfunction, a combined kinematic and electromyographic (EMG) analysis of the upper-trunk bending was performed on 3 patients suffering from progressive cerebellar ataxia of late onset and showing a significant atrophy of the vermis on MRI examination. Compared with 3 age and sex-matched control subjects, a significant slowing down of the upper-trunk displacement and a marked reduction of the associated displacement of hip and knee was observed. EMG recordings of three pairs of antagonistic muscles at trunk level (rectus abdominis, erectores spinae), at thigh level (vastus lateralis, semi membranosus), and at leg level (tibialis anterior, gastrocnemius lateralis), showed that the reciprocal activation pattern characteristic of a normal fast movement was absent at the thigh level in the cerebellar patients. This lack of reciprocal activation of the thigh muscles during the upper-trunk bending might explain the reduction of the compensatory displacement of the hip and knee. It might also represent an essential feature of cerebellar dysfunction in provoking axial asynergia between the upper-trunk, which is the moving segment, and the leg, which is the supporting segment during equilibrium control and during whole body displacement.

Adult↗
PubMed1993

Is the trunk a reference frame for calculating leg position?

Naive subjects and dancers were instructed to raise a leg laterally toward 45 degrees. The final position reached by the leg by each group of subjects was quite different: 48 degrees in dancers, i.e. close to the required value, and 56 degrees in the naive subjects. The reason for this difference was investigated. During the body weight transfer toward the supporting side prior to the leg movement, naive subjects inclined both leg and trunk laterally, whereas the dancers' trunk remained vertical. It was observed that in naive subjects the trunk inclination and the overestimation of the final leg position were closely correlated. The results suggest that in both naive subjects and dancers, the trunk axis serves as a reference value for calculating the leg position.

Adult↗
PubMed1993

[Major anatomico-functional relations in the cerebellum].

In this paper the main anatomico-functional data concerning the cerebellum are presented. The numerous hypotheses put forward on the functions of the cerebellum, such as they are listed in introduction, illustrate both the advances achieved and the problems awaiting to be solved. Following a general view of phylogenesis, the peculiar characteristics of the cerebellar cortex structure are emphasized; they include, notably, the properties of the olivo-cerebellar system, which is a source of climbing fibres and the organization into microzones, which constitutes the basic elements of the cerebellum. Finally, two aspects of functional organization are treated: the definition of three types of cerebellum (vestibular, somaesthetic and visual) based on the sensorial afferent pathways and the definition of efferent functional subsets based on sagittal bands identified in the vermis, the intermediate area and the hemispheric portion.

Afferent Pathways↗
PubMed1993

Axial synergies under microgravity conditions.

Fast forward and backward upper trunk movements were analyzed and compared under microgravity and under preflight and postflight conditions. The kinematic analysis showed that the upper trunk movements were accompanied by hip and knee movements in the opposite direction both under microgravity and under normal gravitational conditions. This suggests that the center of mass position with respect to the feet is still regulated under microgravity when the feet are attached to the floor. The EMG analysis during backward movements shows that under preflight conditions a set of muscles (ErSp, BF, Sol) in the back of the body are activated early on. Under microgravity, the early Sol activation was replaced by an early TA activation, which was still present at the first postflight recording and was then replaced by the early Sol activation observed under preflight conditions. This finding shows that the EMG pattern underlying the axial synergies is flexible and that adaptive changes take place both under microgravity and after return to Earth.

Adaptation, Physiological↗
PubMed1992

Coordination between posture and movement in a bimanual load lifting task: putative role of a medial frontal region including the supplementary motor area.

The aim of the present experimental series was to investigate the role of the medial frontal region including the supplementary motor area in the coordination between posture and movement in a bimanual load lifting task. The seated subject was instructed to maintain in a horizontal position one forearm (postural arm) which was loaded with a 1 kg weight. The unloading was performed either by the experimenter (imposed unloading) or by a voluntary movement of the other arm (voluntary unloading). In normal individuals, with the voluntary unloading, the movement control was accompanied by an anticipatory adjustment of the postural forearm flexor activity, which resulted in the maintenance of the forearm position despite the unloading. The anticipatory postural adjustments were impaired in 4 out of 5 patients with unilateral lesion of the SMA region; the defect was observed mainly when the postural forearm was contralateral to the lesion. No change in the anticipatory postural adjustment was observed in one patient with complete callosal section. This finding indicates that the coordination between the posture and movement in this task is not organized through callosal fibers linking the cortices on both sides but rather at a subcortical level. The anticipatory postural adjustments were abolished in two patients with spastic hemiparesis when the postural forearm was the spastic arm. It is suggested that the SMA region contralateral to the postural forearm, together with other premotor or motor areas, may select the circuits responsible for the phasic postural adjustments which are necessary to ensure postural maintenance, whereas the motor cortex contralateral to the voluntary movement controls both the movement and, via collaterals, the preselected circuits responsible for the associated postural adjustments.

Adult↗
PubMed1992

Coordination between equilibrium and head-trunk orientation during leg movement: a new strategy build up by training.

1. During unilateral leg movements performed while standing, it is necessary to displace the center of gravity toward the other leg to maintain equilibrium. In addition, the orientation of particular segments, such as the head and trunk, which are used as reference values for organizing the motor act, needs to be preserved. The aim of the present study was to investigate the coordination between movement, equilibrium, and local posture. 2. Experiments were carried out on standing subjects who were instructed to raise one leg laterally to an angle of 45 degrees in response to a light. Two sources of light placed in front of the subject indicated the side on which the movement was to be performed. Three main aspects of the posturokinetic sequence were investigated in two populations, naive subjects and dancers: 1) The body weight transfer toward the supporting leg was found to have two components: first, a "ballistic" one, initiated by a thrust exerted by the moving leg; and second, an "adjustment" component during which the displacement of the center of gravity (CG) reaches a final position (steady state). An early burst in the gastrocnemius medialis of the moving leg often precedes the onset of the center of pressure change. Two differences between naive subjects and dancers were observed: first, the new CG position was almost reached in one step very near to the end of the ballistic component and required only a short adjustment in dancers, whereas in naive subjects it was reached in two steps, including a much longer adjustment component. Second, the dancers were able to minimize the CG displacement toward the supporting side; this might be because they form a better internal representation of the biomechanical limits of stability because of their long training. 2) The onset of the lateral displacement of the malleolus marker of the moving leg always occurred when the body weight had almost completed its transfer to above the support foot. This shows that the positioning of the CG in a new position compatible with equilibrium maintenance was a prerequisite for the leg movement to be performed. The relative timing of events during the posturokinetic sequence was fairly fixed in the dancers, whereas it varied from one trial to another in the naive subjects. 3) The coordination between movement, equilibrium, and head-trunk orientation involves two control strategies. An "inclination" strategy was used by the naive subjects; this consisted of an external rotation of the supporting leg around the anteroposterior ankle joint axis. A counter-rotation at the neck level ensured the stability of the interorbital line in the horizontal plane.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

[Strategy and synergy: two levels of equilibrium control during movement. Effects of the microgravity].

Equilibrium is ensured during forward or backward upper trunk movements by displacing the hip and knee simultaneously in opposite directions. When fast movements are performed, a muscle synergy characterized by the early activation of a set of trunk, thigh and leg muscles precedes the onset of the kinematic changes. The question which is addressed concerns the possibility that two levels of equilibrium control might exist during upper trunk movements: the strategy level, which is relatively invariant, is characterized by the displacement in opposite directions of the upper and low segments, and the muscle synergy level at which the strategy is implemented, which may be adaptable to the environmental constraints. When upper trunk movements are performed under microgravity with the subject's feet fixed to the floor of the space cabin, the displacement of upper and lower body segments in opposite directions still occurs, although this is no longer necessary to maintain the equilibrium. This kinematic strategy seems to be aimed at regulating the centre of inertia position with respect to the feet. The muscle synergies associated with these kinematic changes are modified, however, under microgravity. After returning to the ground, the previous synergies do not reappear immediately, but only after a few days. This suggests that a short period of learning is needed to change the synergy. These data are compatible with the hypothesis that two levels of equilibrium control actually exist during upper trunk movements, the strategy level, which is kinematic and invariant, and the synergy level, which is adaptable to the environmental constraints through a short learning process.

Electromyography↗
PubMed1991

[Strategies for simultaneous control of the equilibrium and of the head position during the raising movement of a leg].

The coordination between equilibrium control and the ability to maintain the position of given segments (head, trunk) was studied in standing subjects, instructed to raise one leg laterally at an angle of 45 degrees in response to a light. Two sources of light placed at eye level indicated the side on which the movement was to be performed. Two populations were compared: naive subjects and dancers. Two control strategies were identified. An "inclination" strategy was used by the naive subjects. This consisted of an external rotation of the body around the antero-posterior ankle joint axis; a counter-rotation of the head with respect to the trunk was observed, which ensured some stabilization in the horizontal plane of the interorbital line. A "translation" strategy was used by the dancers. Here the external rotation of the leg around the ankle joint was associated with a feed-forward counter-rotation of the trunk around the coxofemoral joint so that the horizontality of the interorbital line and the verticality of the trunk axis were maintained. This new coordination results from a long-term training and indicates that a new motor program has been elaborated.

Adult↗
PubMed1989

Role of the sensorimotor cortex in postural adjustments accompanying a conditioned paw lift in the standing cat.

The role of the sensorimotor cortex in the postural adjustments associated with conditioned paw lifting movements was investigated in the cat. Cats were trained to stand quietly on four strain gauge equipped platforms and to perform a lift-off movement with one forelimb when a conditioned tone was presented. The parameters recorded were the vertical forces exerted by the paws on each platform, the lateral and antero-posterior displacements of rods implanted on the T2, T12, L5 vertebrae as well as their rotation, and the EMG of triceps and biceps of both forelimbs. Before lesion, the postural adjustment consisted of a "non-diagonal" pattern where the CG was displaced laterally inside the triangle formed by the three remaining supporting limbs. Here a lateral bending of the thoracic column toward the supporting forelimb could be observed. The associated EMG pattern consisted of an early activation of the triceps lateral head in the moving limb which was probably responsible for the body displacement toward the opposite side, and a late biceps activation associated with the lift. In the supporting forelimb, a coactivation of the biceps and triceps was usually present. After contralateral sensorimotor lesion, the conditioned lifting movements were lost for 4-15 days after the lesion, before being subsequently recovered. The same lateral CG displacement and bending of the back was seen after lesion as before, which indicates that the goal of postural adjustment was preserved. However, the means of reaching it were modified.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

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

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.

Adaptation, Physiological↗
PubMed1989

Acquisition of co-ordination between posture and movement in a bimanual task.

The acquisition of co-ordination between posture and movement was investigated in human subjects performing a load lifting task. Sitting subjects held their left (postural) forearm in a horizontal position while supporting a 1 kg load via an electromagnet. Perturbation of the postural forearm position consisted of the load release triggered either by the experimenter (control) or by the subject voluntarily moving the other arm. In the latter case, the movement involved the elbow joint (load lifting (A), isometric force change at the wrist level (B), elbow rotation (C) and pressing a button with the wrist (D] or the fingers (grip isometric force change). We recorded the maximal amplitude and maximal velocity of the rotation of the postural forearm, the EMG of the forearm flexors on both sides and the force exerted either by the load on the postural arm or by the isometric contraction of the moving arm. The maximal forearm angular velocity after unloading was known to be related to the level of muscle contraction before unloading. 1. In the control situation, repetition of the imposed unloading test resulted in a progressive reduction in the maximal forearm rotation without any decrease in the maximal velocity. The amplitude and duration of the unloading reflex were found to increase in parallel. These results suggest that an adaptive mechanism took place which increased the gain of the unloading reflex loop and reduced the mechanical effect of the perturbation. This mechanism was found to come into play not only in the control situation but also in other paradigms where the perturbation was expected by the subjects. 2. A decrease in both maximal amplitude and velocity of forearm rotation together with a weak "anticipatory" deactivation of the forearm postural flexors was observed when the unloading was caused by an elbow movement (situations A, B, C) which indicates that a feedforward postural control took place. An interlimb coordination was built up and stabilized after 40-60 trials. Pressing a button with the wrist (weak force and displacement) was a less effective means of inducing an anticipatory control of the flexors of the postural forearm, which indicates that the intensity of the central control plays a role in the building up of the coordination. 3. A distal grip action exerting either weak (100 g) or a high (1 kg) force was able to reduce the maximal amplitude of the forearm rotation, but not the maximal velocity, which indicates that an improved reflex action takes place, but not a feedforward anticipatory postural control.(ABSTRACT TRUNCATED AT 400 WORDS)

Elbow Joint↗
PubMed1989

[The supplementary motor area is implicated in the coordination between posture and movement in man].

The aim of the present experimental series was to investigate the central organization of the coordination between posture and movement in a bimanual load lifting task. The seated subject was instructed to maintain horizontal one forearm (postural arm) which was loaded with a 1 kg weight. The unloading was performed either by the experimenter (imposed unloading) or by a voluntary movement of the other arm (bimanual unloading). With the bimanual unloading, the movement control was accompanied by an anticipatory adjustment of the postural forearm flexors activity, which resulted in the maintenance of the forearm position despite the unloading. No change in the anticipatory postural adjustment was observed in one patient with complete callosal section. It was reduced in 5 patients with lesion of the SMA region, but only when the postural forearm was contralateral to the lesion. It is suggested that the SMA region contralateral to the postural forearm may select the circuits responsible for the phasic postural adjustments which are necessary to ensure postural maintenance, whereas the motor cortex contralateral to the voluntary movement controls both the movement and, via collaterals, the preselected circuits responsible for the associated postural adjustment.

Adult↗
PubMed1987

Forward and backward axial synergies in man.

Upper trunk and head forward and backward movements were analyzed in human subjects standing on a force platform. EMG of several flexor and extensor muscles was recorded together with the kinematics of the movement (EL.I.TE. system). It was found that upper trunk movements are accompanied by movements of hip and knees in the opposite direction, resulting in a slight displacement of the center of gravity projection on the ground. In fast movements, all the body segments were displaced at the same time, which suggests a feedforward control, whereas in slow movements, onset of displacement of the body segments was found to take place sequentially in a cranio-caudal direction. EMG analysis during fast movements revealed two different types of control, utilized in forward and backward movements. With forward bending movements the action of two sets of muscles could be recognized: the prime mover (R. Abd.), the activation of which was not correlated with that of the other muscles and preceded the onset of movement with a fairly constant lead, and a group of postural muscles, the activation (VM, TA) and inhibition (Sol) of which were closely correlated. By contrast, with backward movements, the prime mover (Er.S.) and the postural leg muscles (Hamstrings, Sol) were activated simultaneously. In both cases, a feedforward type of control is evident. Performance of the fast forward movements was accompanied by an initial forward displacement of the knee. The function of this phenomenon is discussed in term of a destabilizing action favouring the forward bending of the body or a prestretching of the knee extensor muscles increasing the strength of their subsequent contraction.

Adult↗
PubMed1987

Performance of a bimanual load-lifting task by parkinsonian patients.

Normal subjects and Parkinsonian patients performed a bimanual load lifting task. In this task, one "postural" forearm, held in a horizontal position while supporting a 1 kg weight, was unloaded either by the experimenter's hand (imposed unloading) or by the subject's other hand in response to a tone burst (voluntary unloading). The variables recorded were reaction time (RT: time interval between the tone and beginning of unloading) and movement time (MT: duration of the change in force measured by a force platform on the "postural" forearm). Elbow angle changes were also measured with a potentiometer. The EMG activity from brachioradialis of the "postural" arm and that from the biceps of the "active" arm were recorded. The Parkinsonian patients showed an increase in both RT and MT and an impairment of the co-ordination between movement and posture which was reflected in an increase in amplitude of the elbow rotation after voluntary unloading. Moreover, the decrease in EMG activity in the brachioradialis of the postural arm during unloading was less in Parkinsonian patients than in the normal group. This disorder of postural command was often accompanied by a lack of anticipatory EMG changes. Comparison between treated and non-treated patients showed that dopamine agonists brought about recovery of both RT and MT but did not improve postural co-ordination. The co-ordination was less impaired when the voluntary unloading was performed by the preferred hand. Several hypotheses are discussed concerning the mechanism underlying this impaired co-ordination.

Aged↗