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At least 415 records · Page 23Linked to original sources
PubMed1990

The postnatal development of the air-righting reaction in albino rats. Quantitative analysis of normal development and the effect of preventing neck-torso and torso-pelvis rotations.

The aim of this study was to describe the ontogenesis of the air-righting reaction (ARR) in rats. The first experiment was performed on 6 newborn albino rats of both sexes and followed the development of the ARR over postnatal days 1-21. The degree of rotation achieved after falling from different heights was quantified according to a rating scheme. It appeared that the air-righting reaction is effected by a spiral movement which spreads in a cranio-caudal direction. The reaction develops between postnatal day 8 and 18. On postnatal day 10 only a few animals are able to turn their heads, this being possible only from a falling height of 60 cm and corresponding to a falling time of 350 ms. A rapid development of the reaction was found between days 10 and 14. The second experiment on 8 rats involved the use of immobilization in order to isolate the mechanisms that trigger the ARR. The immobilization prevented neck-torso rotation, torso-pelvis rotation, and both rotations in different animals. Despite the disruption of important (afferent) feedback systems, the reaction developed within the same age period as in control rats. Thus, the Magnus "chain reflex hypothesis' as basis for the ARR is rejected in favor of a central motor program hypothesis.

Age Factors↗
PubMed1993

Haloperidol exaggerates proprioceptive-tactile support reflexes and diminishes vestibular dominance over them.

Rats made immobile and cataleptic by haloperidol, a dopamine receptor blocker, maintain their static stable equilibrium by employing a variety of allied postural support reflexes. Under some test conditions, competition between such reflexes occurs, and in haloperidol-treated rats, unlike undrugged controls, proprioceptive-tactile stimuli appear to be dominant over vestibular stimuli. We investigated this relationship in rats by testing their air-righting with and without simultaneous contact of the tail on a wooden platform. The rats were lightly held in a supine position by the shoulders and pelvis, with or without tail contact on a small wooden platform 47 cm above the ground. Undrugged rats showed the normal pattern of righting which involves axial rotation with cephalocaudal recruitment whether the tail is contacting the platform or not. Upon release, the haloperidol-treated rats (2.5 mg/kg) gripped the platform with their tail, which interfered with the air-righting reflex. This demonstrates that in haloperidol-treated rats, the dominance of tactile-proprioceptive postural support reflexes over those triggered vestibularly.

Animals↗
PubMed1993

Neurological and behavioral effects of a unilateral frontal cortical lesions in fetal kittens. I. Brain morphology, movement, posture, and sensorimotor tests.

Nine fetal kittens sustained removal of the left frontal cortex during the last third of gestation (E 43-55) and were compared to animals sustaining a similar lesion postnatally (P 8-14) as well as to littermate controls. Starting after 6 months of age the animals received a comprehensive battery of movement, posture and sensorimotor tests. The prenatal-lesioned cats performed worse in practically all 15 tests applied (significantly in 13 of them) compared to the neonatal-lesioned cats. Impairments included contralateral paresis of the limbs and face, defective limb placing reactions (with almost absence of the contact components) and a slight extensor hypertonus; tactile hypoesthesia in the contralateral face and hind paw; a bias not to use the contralateral forepaw in a food retrieval task, and an ipsilateral body turning bias. The neonatal-lesioned animals only showed minor defects in the contact components of the limb placing reactions and a tendency to a body turning bias. Morphologically, the brains of the prenatal-lesioned cats, but not of neonatal-lesioned or intact control cats, showed bilateral disruption of the cortical sulcal and gyral patterns, shrinkage of the ipsilateral hemisphere, and reduction in volume of the ipsilateral thalamus and cortex. We concluded, contrary to expectations, that the consequences of a prenatal brain lesion in the cat are worse than when a similar lesion is sustained neonatally.

Animals↗
PubMed1994

Making two movements at once: impairments of movement, posture, and their integration underlie the adult skilled reaching deficit of neonatally dopamine-depleted rats.

Adult rats depleted bilaterally of dopamine in infancy display a profound impairment in skilled forelimb use in reaching for food. This impairment was investigated using end-point measures of reaching success, movement analysis, and kinematic measures. The rats made few successful reaches in either an easy or a difficult reaching test. Their reaches were characterized by many attempts in which trajectories of the limb were irregular and the movements were slow. Their lack of success was related in part to an impairment in making component movements of the reach, including aiming, pronating, grasping, and supinating the paw and in releasing the food pellet. It was also related to an inability to adjust posture as the limb was voluntarily moved toward the food. The results are consistent with the hypotheses that the basal ganglia, including its dopamine innervation, is important for enabling voluntary movements and postural adjustments and perhaps also the simultaneous performance of two movements at the same time.

Aging↗
PubMed1996

Varieties of paw and digit movement during spontaneous food handling in rats: postures, bimanual coordination, preferences, and the effect of forelimb cortex lesions.

This study describes how rats use their paws and digits when handling a wide range of foodstuffs, including food pellets, grapes, sunflower seeds, shelled and unshelled peanuts, and different sized pastas, etc. Analysis of videorecordings show that the rats display digit postures that include variations in the spacing of the digits, differences in the relative use of different digits, and interlimb differences in paw and digit posture. The rats also display limb preferences in that one paw is used in a supporting function while the other rotates, flips, or pushes the food as is required by the shape of the item. There is a significant correlation between the paw used for manipulation and food items of similar shape but no correlation between the limb used for manipulation and that used for skilled reaching. Small unilateral lesions to the forepaw area of somatic sensorimotor cortex produced impairments in use of the paw contralateral to the lesions. These results: (1) reveal a surprising complexity in the way in which rats use their paws and digits in manipulating food; (2) show that rats have limb preferences in spontaneous food handling; and (3) show that manipulatory dexterity is dependent upon the integrity of the forelimb area of motor cortex. The results are discussed in relation to the evolution of motor skill, the use of rats for investigating questions of motor system organization, neural plasticity, and recovery of function after brain damage.

Animals↗
PubMed1996

A behavioral study of the development of hereditary cerebellar ataxia in the shaker rat mutant.

shaker Mutant rats were first identified by their abnormal motor behaviors and degeneration of cerebellar Purkinje cells and brainstem inferior olivary neurons. After 6 generations of inbreeding 77% of shaker rat mutants are mildly ataxic (identified as mild shaker mutants) and 23% are ataxic and exhibit a whole body tremor (strong shaker mutants) by 3 months of age. This study of shaker mutants from birth to 3 months of age was designed to: (1) compare the somatic and motor development of shaker mutants with age matched normal rats; (2) identify the temporal onset of motor deficits; and (3) correlate qualitative differences in Purkinje cell degeneration between 3-month-old mild and strong shaker rat mutants. Shaker mutant rats consistently weighed less than age-matched control animals. Analysis of motor-development using the hindlimb splay test demonstrated the distance between hindpaws was significantly greater in shaker mutant rats than in controls starting at 42 postnatal days (PND) of age. Hindlimb stride width was greater for shaker than control rats at 42 PNDs. However, after 42 PNDS shaker mutant average hindlimb width was narrower than controls. Forelimb stride width was consistently narrower in shaker mutants than in normal rats. Hindlimb placement was impaired in shaker rat mutants after 15 PND. Forelimb placement, cliff avoidance and surface righting were only transiently impaired in shaker mutants. Mid-air righting, performance of a geotaxic response, and climbing and jumping postural reactions were similar in shaker and normal rats. The spatial extent of Purkinje cell survival/degeneration correlated with differences in abnormal motor activity seen in 3-month-old mild and strong shaker mutants. In mild shaker rat mutants, Purkinje cells appeared to have degenerated randomly throughout the cortex. In strong shaker mutants most Purkinje cells in the anterior lobe had degenerated. In the posterior lobe Purkinje cell degeneration appeared to be numerically significant, but many surviving cells were present. Although Purkinje cell loss was not numerically quantified in this study, a strong association between the extent and type of spatial loss of Purkinje cells, and the severity of clinical signs, appears to exist.

Animals↗
PubMed1996

Influence of the initial projection of the centre of gravity on posturo-kinetic coordination in humans. Application from a horizontal quadrupedal stance during voluntary limb raising.

The purpose of the study is to investigate the influence of initial projection of the centre of gravity (CG) on the spatial and temporal organization of the dynamic phenomena accompanying a voluntary movement in humans. From a horizontal quadrupedal stance, ten normal subjects were instructed to raise the right forelimb towards a support target in self paced velocity conditions. Three experimental conditions were tested for which the initial CG projection was either within (C1), at the limits of (C2) or outside the supporting triangle (C3). The results showed that vertical force variations on the four supports always preceded the first vertical displacement of the right wrist (onset of the movement). From C1 to C3, the duration of these anticipatory dynamic phenomena increased enabling an adjustment of the CG position such that equilibrium constraints were fulfilled. For all conditions, the acceleration peak of the CG occurred prior to the onset of movement and from C1 to C3, its magnitude increased in a single direction of the horizontal plane. For each condition, the load transfer was directed to the left forelimb and the right hindlimb (diagonal strategy) and reached a maximal value at the time of lift-off. With respect to this moment, the onset of the movement occurred increasingly early from C1 to C3. These results suggest that contribution of peripheral cues to postural control is more important, when the requirements of horizontal CG displacement increase.

Adult↗
PubMed1995

Rotorod sensorimotor learning in cerebellar mutant mice.

Lurcher mutant mice, characterized by degeneration of cerebellar granule and Purkinje cells, were compared to normal littermate controls in a rotorod test, consisting of a wheel turning at constant speed which required on the part of the animal postural adjustments in order to maintain equilibrium. Identical baseline rates for the two groups were assured by changing the speed and size of the rotating rod. Although both groups were able to learn the task, the fall latencies of normal mice exceeded those of lurchers. These results indicate that cerebellar cortical atrophy does not abolish this form of sensorimotor learning. However, brain-damaged animals are unable to reach the same level of performance as normal animals. In contrast to the results in lurcher mutants, no sensorimotor learning was displayed by hot-foot mutants and staggerer mutants.

Animals↗
PubMed1994

The limits of equilibrium in young and elderly normal subjects and in parkinsonians.

Body sway was studied at various body inclinations, voluntarily maintained for about 1 min, in young and elderly normals and in idiopathic parkinsonians. They stood on a dynamometric platform, whose output gave the instantaneous centre of foot pressure (CFP), its mean value and body sway area, with eyes open (EO) or closed (EC). Subjects held the normal upright stance, or the maximum possible inclined posture (body straight, rotated at the ankle joints) in forward or backward direction, or intermediate postures. EMG was recorded from tibialis anterior (TA), soleus (Sol), extensor digitorum brevis (EDB) and flexor digitorum brevis (FDB). The cross-correlation function between the profile of the EMG envelope and the profile of the shift of CFP along the sagittal plane was calculated. In young subjects standing with EO, the maximum extent of antero-posterior (A-P) displacement of CFP was about 60% of foot length. EC reduced this value to about 50%. In the elderly normals, the maximum A-P displacement was about 40% (EO) and 30% (EC). In both groups, sway area was minimal during normal stance with EO and increased progressively when the subjects leant forward or backward. With EC, sway area further increased during normal stance and the rate of increase in relation to inclination augmented markedly. Sol was tonically active during normal stance. Forward leaning increased Sol EMG and induced activity in FDB. TA and EDB were active during backward leaning. The peak of the cross-correlation function between Sol EMG and instantaneous CFP was higher during normal stance than forward inclination, while the reverse was true for FDB. This suggests a role of FDB in the fine-tuning of postural adjustment during forward leaning, and a weight-supporting role of Sol. During backward inclination, TA but not EDB was cross-correlated with CFP. In the parkinsonians, maximum A-P displacement of CFP was just about 30% of foot length (EO; about 20% with EC); its extent was inversely correlated with the severity of the disease. The relationship between sway area and A-P displacement was similar to the elderly, both with EO and EC, within the common range of inclination. In the patients affected by the long-term syndrome, A-P displacement was further reduced while sway area increase at the critical postures was often absent. In all patients, the relationship between muscle activity and body inclination was comparable to normal.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMedDate not supplied

Positional nystagmus and body sway after alcohol ingestion.

Positional nystagmus and body sway were measured for 8 hours following alcohol ingestion in 27 human volunteers. The intensity of positional alcohol nystagmus phase I (PAN-I) correlated well with blood alcohol concentration (BAC) along the time axis; the correlation coefficient between PAN-I and BAC 1 hour after alcohol ingestion was 0.62 (P less than .01). The minimum threshold BAC resulting in PAN-I was 0.23 mg/mL. Body sway was measured by stabilometry. The circumscribed area of posturography before and after alcohol ingestion was compared. Temporal changes in body sway and BAC were also closely correlated. The BAC threshold for increased body sway was estimated to be somewhere between 0.5 and 0.8 mg/mL, considerably higher than the threshold for PAN-I. Measurements of blood acetaldehyde, the dehydrated product of ethanol metabolism, showed no correlation with either the intensity of PAN or changes in body sway. The intensity of PAN and body sway measured at the time of peak BAC 1 hour after alcohol ingestion, however, showed significant positive correlation (r = .50, n = 25; P less than .01).

Acetaldehyde↗
PubMedDate not supplied

Chronic toxic encephalopathy investigated using dynamic posturography.

Seven male patients previously exposed to industrial solvents and diagnosed with chronic toxic encephalopathy (aged 38 to 69 years; mean age, 56 years) were investigated by dynamic posturography and compared with healthy, age-matched male control patients. Dynamic posturography comprises two phases: a sensory organization (SO) phase, in which the support surface and visual surround are either stable or referenced to the patient's sway, with eyes open or closed, and a movement coordination (MC) phase, in which the platform makes active movements. In SO testing, the patient group showed significantly impaired equilibrium performance compared with the control group in most test conditions. The MC test revealed no differences between groups. A relationship was found between the equilibrium score resulting from SO testing with stable support and visual surround and the sway area of the confidence ellipse elicited 3 years previously by static posturography with eyes open. We conclude that patients with chronic toxic encephalopathy have impaired equilibrium, as demonstrated by dynamic posturography testing.

Adult↗
PubMed1989

Dorsal light response and changes of its responses under varying acceleration conditions.

In order to improve our understanding about functions of the gravity sensors, we have conducted four experiments in goldfish: 1) To define the effect of visual information influx on the static labyrinthine response, the dorsal light response (DLR) which had been proposed by von Holst as a model for postural adjustment in fish was reexamined with a newly designed, rotatory illumination device. The fish responded to illumination from the upper half of the visual field and a narrow range around 180 degrees of the lower half visual field. The maximal tilting angle of normal fish was about 40 degrees under horizontal illumination. 2) Under the changes of the gravito-inertial force level produced by a linear sled, the threshold of the gravity sensors was determined from postural adjustment responses. 3) Under hypogravic conditions during the parabolic flight of an airplane, the light-dependent behavior was investigated in intact and labyrinthectomized goldfish. 4) As one of the most likely candidates of the neural centers for the DLR, the valvula cerebelli, which receives its visual information not through the optic tectum but through the pretectal areas, is confirmed by the brain lesion experiments.

Acceleration↗
PubMed1982

Influence of static tilt on soleus motoneuron excitability in man.

The influence of whole head-body rotations with respect to gravity on the excitability of the human soleus motoneuron pool, was studied by mapping the H reflex amplitude as a function of static head displacements. In most subjects, the H reflex reached a minimum when the head was near the vertical position (90 degrees), and often increased as a sinusoidal function of tilt in the sagittal plane. These changes were attributed to the tonic labyrinthine reflexes which, unlike some findings in decerebrate cats, generally increase the extensor tone of the human lower limb when the head is displaced from the upright position.

H-Reflex↗
PubMed1992

Do fast voluntary movements necessitate anticipatory postural adjustments even if equilibrium is unstable?

Anticipatory postural adjustments (APA) were studied in maximum velocity flexion of lower limb from two initial postures, a bipedal stance (Fbu) and unipedal stance (Fuu). In Fbu, the dynamics of center of gravity (CG) and ankle and hip muscle EMG activity showed large APA. In contrast, in Fuu there were no APA, the CG dynamics and the ankle EMG activity started at the same time as the intentional movement while the hip EMG activity started some 30 ms before the thigh flexion. The knee flexion velocity was lower in Fuu than in Fbu (7 rd/s versus 12 rd/s). These results suggest that fast voluntary movements do not require APA when the postural equilibrium is unstable, and that an alternative strategy is used. The absence of APA in Fuu, in contrast to the presence of APA in Fbu, suggests that the postural command and the focal one are time-locked and organized in a parallel process.

Electromyography↗
PubMed1995

Early activation of arm muscles follows external perturbation of upright stance.

Grasping, counterbalancing and protective arm movements are an important defence against external postural perturbation, but are commonly constrained in studies of postural control. We measured muscle activity at the shoulder, and the lower leg, during unconstrained responses to platform translation. Results revealed very early activation in shoulder muscles, similar in timing to the 'automatic' ankle responses. The arm activation occurred even when the reaction provided no immediate defence against destabilization but would appear to be more than a 'startle' response, since the activation was scaled to the perturbation magnitude and persisted even when perturbations were expected. The arm activation would appear to be driven from a remote sensory source, since there was negligible loading or stretch of the arm muscles.

Adult↗
PubMed1994

The development of a battery of measures for assessing physical functioning of chronic pain patients.

The physical performance of chronic pain patients is of major concern both for their assessment and for treatment evaluation. However, there are few widely used physical tests, a shortage of reliability and validity data on published tests, and an over-reliance on self-report or on clinical measures of dubious generalisability. A set of tests was designed to cover speed and endurance in walking, stair climbing, standing up from a chair, sit-ups, arm endurance, grip strength, and peak flow. Standard instructions and testing conditions were used by a trained tester on a population of chronic pain patients before and after a cognitive-behavioural chronic pain management programme. Reliability, validity, and acceptability of each test was examined, and recommendations made for their relative utility.

Adult↗