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PubMed1991

Postural stability on moving platform oscillating at high frequencies. Effect of vestibular lesion.

The effect of linear perturbation at a frequency range of 8 to 24 Hz on postural stability was studied in 7 patients with unilateral vestibular function loss. Force platform technique was used with automatic analysis resulting in the sway velocity of the center point of force. In all patients the support surface movement produced increased sway velocity which was significantly greater than in the controls. Tests at lower frequencies (8 and 10 Hz) produced higher sway velocities than tests at higher frequencies (12, 14, 16 and 24 Hz). The results indicate that the vestibular system controls postural reflexes at a substantially higher frequency range than hitherto suggested.

Adult↗
PubMed1989

Dependent oedema and attenuation of postural vasoconstriction associated with nifedipine therapy for hypertension in diabetic patients.

We studied the incidence of oedema 2 weeks following initiation of nifedipine therapy for hypertension in a group of 10 diabetic subjects, and also measured skin blood flow (SBF) with a laser Doppler flowmeter, before and after lowering the foot. SBF with the foot horizontal increased after nifedipine from 0.31 V (arbitrary units of flow) to 0.51 V (NS). The postural fall in blood flow in dependency was significantly attenuated by nifedipine from 64.4 to 24.0%. Five patients developed ankle oedema. Results were similar in a small group of non-diabetic subjects starting nifedipine. The attenuation of reflex postural vasoconstriction is therefore likely to contribute to development of the oedema associated with starting nifedipine therapy, which should be monitored carefully in diabetic patients.

Adult↗
PubMed1993

Activity of neurons in the beta nucleus of the inferior olive of the rabbit evoked by natural vestibular stimulation.

The inferior olive (IO) appears to be organized functionally in discrete subnuclei that receive transmitter-specific inputs. In particular, the IO receives a GABAergic input that is most densely concentrated in the beta-nucleus. In this experiment, we examined the functional specificity of neurons in the beta-nucleus of the IO of rabbits by recording their activity during natural vestibular and optokinetic stimulation. Rabbits were anesthetized and positioned in a triaxial servo- controlled rate table with the head fixed at the center of rotation. Contour-rich visual stimuli were rear-projected onto a 70 deg tangent screen and moved at constant velocities. Recording sites in the beta-nucleus were verified by subsequent histological analysis of marking microlesions. Neurons in the beta-nucleus responded to roll vestibular stimulation about the longitudinal axis. These neurons were excited when the rabbit was rolled onto the side which was contralateral to the recording site, and inhibited when the rabbit was rolled ipsilaterally. Thirty-eight of the 75 beta-nucleus neurons that were responsive to roll vestibular stimulation also responded to static tilt, indicating an otolithic as well as a vertical semicircular canal origin of the vestibular input. The modulated activity of none of the neurons could be attributed to stimulation of the horizontal semicircular canals. All the recorded neurons were found in a region of the beta-nucleus that was retrogradely labeled following HRP injections into the cerebellar nodulus. Using a "null point" technique, we found that there was a differential projection of information from the anterior and posterior semicircular canals onto to the beta-nucleus. Stimulation of the ipsilateral anterior-contralateral posterior semicircular canals modulates activity of the neurons in the caudal 500 microns of the beta-nucleus. Stimulation of the ipsilateral posterior-contralateral anterior semicircular canals modulates activity of neurons located more rostrally. beta-nucleus neurons and the olivocerebellar circuits in which they participate may constitute an important pathway for the control and adaptive modification of postural reflexes.

Action Potentials↗
PubMed1988

Development of the central nervous system functions in rat pups prenatally exposed to alcohol (study on the behavioural teratology of ethanol in CFY rat pups).

As a model of fetal alcohol syndrome (FAS) the rate of the maturation of the functions of the central nervous system was studied in the offspring of pregnant CFY rats receiving (from the 7th-15th day of gestation) either oral ethanol treatment or liquid diet containing ethanol. Both types of exposure caused numerous behavioural impairments, besides high perinatal mortality also the opening of the eyes and ears, and the appearance of postural reflexes were delayed. The newborn rats could be characterized by hyperactivity and weak motor coordination. The learning capacity, the avoidance conditioned reflexes was the poorest in the case of the offspring of mothers kept on liquid diet, containing alcohol, the latency of the conditioned response was significantly lenghtened. During reconditioning, in the case of the sexually already mature pups, the weakest performance was observed in the offspring of mothers having received oral alcohol treatment. This findings indicated, on one hand, that the retardation ceased and, on the other, that the learning and memory impairments caused by oral alcohol exposure was persistent. Following prenatal alcohol exposure carried out by different methods the neurotoxic effect, the retardation of the rate of maturation of the central nervous functions, and the adaptive mechanisms were all affected to different extent. Besides alcohol exposure also other factors (relative protein insufficiency, malnutrition) may be involved in the pathomechanism of the above mentioned phenomena.

Aggression↗
PubMedDate not supplied

[The risk of falling due to benzodiazepine administration, alone or in combination, in elderly subjects].

Benzodiazepines are well tolerated by young adults whereas in elderly people they are less safe and globally induce more central nervous system side-effects and falls. Falls result from a decrease of vigilance and an alteration of postural reflex. This latter includes the reception of sensory information and central integration modulated mainly by dopaminergic D2 receptors and motor stimulation. Benzodiazepines act simultaneously on the three stages, decreasing their efficacy. The risk increases when certain other drugs are coprescribed, especially synergistic drugs such as another psycholeptic drug, an aminoside or a centrally active antihypertensive drug. Thus their co-prescription with a benzodiazepine increases the risk of falls. The pharmacokinetic parameters of benzodiazepines may be modified or remain constant during ageing. The choice of molecules whose parameters do not vary seems advisable. Whatever the selected benzodiazepine, it is obvious that it must be administered at the lowest possible dose, this dose being increased only if necessary, the overall prescription being time limited.

Accidental Falls↗
PubMed1993

Methods to assess the development and recovery of locomotor function after spinal cord injury in rats.

The ability to assess recovery of function after spinal cord injury is a very important part of spinal cord injury research. Recent progress has been made in a number of avenues of treatment designed to ameliorate the consequences of spinal cord injury and enhance recovery of function. This potential for intervention to modify the sequellae of spinal cord injury requires stringent criteria for methods used to evaluate the effects of injury and subsequent recovery of function. Methods which rely on composite ratings of an animal's overall performance, while appropriate for screening groups of animals with spinal cord injury, are not sufficient to demonstrate whether a particular treatment has had a specific effect on motor function or the degree to which function is affected. We have designed a series of sensitive quantitative methods to assess the recovery of locomotor function in rats. The methods examine specific reflex responses and specific components of motor behavior and are sensitive to subtle differences in the pattern of locomotion and individual limb movements. Several of the tests can be used to assess the development of locomotor function as well as the mature response. Postural reflex testing and locomotor function under conditions of graded difficulty are examined and the motor capacity of individual limbs is assessed. Animals are trained to cross runways, to walk on a treadmill, and to climb onto a platform. The animals' performance is videotaped for subsequent quantitative analysis. The pattern of overground and treadmill locomotion is also examined by footprint analysis. Spinal cord injury alters an animal's reflex responses and deficits are evident in locomotor function. Examples are given of the quantitative measurements obtained from analysis of the animals' performance on each of the tests. No single test is sufficient to assess recovery of function after spinal cord injury. Rather, a combination of tests, each examining particular components of normal and recovered motor function, is required. The methods used to assess recovery of locomotor function are specific, are sensitive, and allow individual limb movements to be isolated. Such specific methods allow one to begin to address the mechanisms underlying recovery of function following spinal cord injury.

Animals↗
PubMed1978

The neurological manifestations of chronic inhalation of leaded gasoline.

Abnormal neurological signs were found in 46 of 50 children and adolescents chronically sniffing leaded gasoline. These abnormalities resolved within eight weeks in all but one case. Exaggerated deep reflexes, postural tremor and evidence of cerebellar dysfunction occurred in a highly significnat number of patients. Forty-nine had blood lead levels greater than or equal to 40ug/dl. The mean blood lead levels were significantly higher in those with (a) abnormally brisk deep reflexes and (b) with evidence of cerebellar dysfunction, than in those without these findings. Five optional treatment regimes were employed and a classification was used, based on clinical findings, initial blood lead levels and the response to the calcium disodium edatate mobilization test. 39 patients received chelation therapy. These data suggest that neurological manifestations occur frequently in those abusing leaded gasoline and that chelation therapy has an important place in their management.

Adolescent↗
PubMed1998

Neuronal mechanisms underlying the facilitatory control of uropod steering behaviour during treadmill walking in crayfish. I. Antagonistically regulated background excitability of uropod motoneurones

One of the postural reflexes of crayfish, the uropod steering response, is elicited by specific sensory inputs while the animal is walking. It is not elicited, however, by the same inputs when the animal is at rest. To clarify the neuronal mechanisms underlying this facilitatory control of body posture in the active animals, we used intracellular recordings to analyse the synaptic activities of uropod motor system neurones in an unanaesthetized whole-animal preparation. Several uropod motoneurones were found to receive sustained depolarizing inputs during walking, whereas the walking leg motoneurones sampled always showed rhythmic activity. The membrane conductance of the uropod motoneurones increased during the sustained synaptic activity. Premotor nonspiking interneurones showed depolarizing or hyperpolarizing membrane potential changes during walking that were also accompanied by increases in membrane conductance. Some of these interneurones enhanced uropod motoneurone activity, whereas others suppressed it during walking. These results suggest that the background excitability of uropod motoneurones is kept at an intermediate level during walking by the antagonistic inputs from premotor nonspiking interneurones so that the uropod motor system can be responsive to both further excitatory and inhibitory inputs resulting from postural changes.

Journal Article↗
PubMed1985

Effects of a commercial soy lecithin preparation on development of sensorimotor behavior and brain biochemistry in the rat.

Pregnant rat dams and offspring were exposed to a 5 or 2% soy lecithin preparation or a control diet. Enrichment was either lifelong beginning at gestation, limited to the time preceding, or the time following weaning, or absent (constituting a "pure" control group). The most marked early sensorimotor deficits (reflex righting and swimming development) were seen in the 5% soy lecithin preparation group, although all soy lecithin preparation-exposed offspring had elevated brain/body weight ratios and choline acetyltransferase levels. Later, animals exposed to lifelong 5 or 2% soy lecithin preparations were hypoactive, had poor postural reflexes, and showed attenuated morphine analgesia. The results indicate that dietary soy lecithin preparation enrichment during development leads to behavioral and neurochemical abnormalities in the exposed offspring.

Animals↗
PubMedDate not supplied

Participation of the nigro-striatal and mesolimbic dopaminergic systems of the brain in the control of components of learned motor responses in dogs.

We studied the role of the striatal and limbic dopaminergic systems in the regulation of instrumentally conditioned avoidance behavior and postural adjustment in chronic experiments on dogs. Dopamine in doses of 3 micrograms was introduced bilaterally into the caudate nucleus head and the nucleus accumbens of the forebrain through implanted cannuli. Predominantly unidirectional effects were demonstrated, but a clear acceleration of the initiations of both conditioned-reflex postural adjustment and voluntary movement were obtained from the caudate nucleus; there was a marked degree of expressiveness to this movement. The greatest effects were obtained during simultaneous, bilateral introduction of dopamine into both structures in dogs with an akinetic form of motor pathology. We conclude that the integration of the striatal and limbic dopaminergic systems is of critical necessity for the initiation and regulation of the components of voluntary movement.

Animals↗
PubMed2006

Evidence for abnormal early development in a mouse model of Rett syndrome.

Rett syndrome (RTT) is a neurodevelopmental disorder that affects mainly females, associated in most cases to mutations in the MECP2 gene. After an apparently normal prenatal and perinatal period, patients display an arrest in growth and in psychomotor development, with autistic behaviour, hand stereotypies and mental retardation. Despite this classical description, researchers always questioned whether RTT patients did have subtle manifestations soon after birth. This issue was recently brought to light by several studies using different approaches that revealed abnormalities in the early development of RTT patients. Our hypothesis was that, in the mouse models of RTT as in patients, early neurodevelopment might be abnormal, but in a subtle manner, given the first descriptions of these models as initially normal. To address this issue, we performed a postnatal neurodevelopmental study in the Mecp2(tm1.1Bird) mouse. These animals are born healthy, and overt symptoms start to establish a few weeks later, including features of neurological disorder (tremors, hind limb clasping, weight loss). Different maturational parameters and neurological reflexes were analysed in the pre-weaning period in the Mecp2-mutant mice and compared to wild-type littermate controls. We found subtle but significant sex-dependent differences between mutant and wild-type animals, namely a delay in the acquisition of the surface and postural reflexes, and impaired growth maturation. The mutant animals also show altered negative geotaxis and wire suspension behaviours, which may be early manifestations of later neurological symptoms. In the post-weaning period the juvenile mice presented hypoactivity that was probably the result of motor impairments. The early anomalies identified in this model of RTT mimic the early motor abnormalities reported in the RTT patients, making this a good model for the study of the early disease process.

Animals↗
PubMed1997

Sacculocollic reflex arcs in cats.

Neuronal connections and pathways underlying sacculocollic reflexes were studied by intracellular recordings from neck extensor and flexor motoneurons in decerebrate cat. Bipolar electrodes were placed within the left saccular nerve, whereas other branches of the vestibular nerve were removed in the inner ear. To prevent spread of stimulus current to other branches of the vestibular nerve, the saccular nerve and the electrodes were covered with warm semisolid paraffin-Vaseline mixture. Saccular nerve stimulation evoked disynaptic (1.8-3.0 ms) excitatory postsynaptic potentials (EPSPs) in ipsilateral neck extensor motoneurons and di- or trisynaptic (1.8-4.0 ms) EPSPs in contralateral neck extensor motoneurons, and di- and trisynaptic (1.7-3.6 ms) inhibitory postsynaptic potentials (IPSPs) in ipsilateral neck flexor motoneurons and trisynaptic (2.7-4.0 ms) IPSPs in contralateral neck flexor motoneurons. Ipsilateral inputs were about twice as strong as contralateral ones to both extensor and flexor motoneurons. To determine the pathways mediating this connectivity, the lateral part of the spinal cord containing the ipsilateral lateral vestibulospinal tract (i-LVST) or the central part of the spinal cord containing the medial vestibulospinal tracts (MVSTs) and possibly reticulospinal fibers (RSTs) were transected at the caudal end of the C1 segment. Subsequent renewed intracellular recordings following sacculus nerve stimulation indicated that the pathway from the saccular nerve to the ipsilateral neck extensor motoneurons projects though the i-LVST, whereas the pathways to the contralateral neck extensors and to the bilateral neck flexor motoneurons descend in the MVSTs/RSTs. Our data show that sacculo-neck reflex connections display a qualitatively bilaterally symmetrical innervation pattern with excitatory connections to both neck extensor motoneuron pools, and inhibitory connections to both neck flexor motoneuron pools. This bilateral organization contrasts with the unilateral innervation scheme of the utriculus system. These results suggest a different symmetry plane along which sacculus postural reflexes are organized, thus supplementing the reference planes of the utriculus system and allowing the gravistatic system to represent all three translational spatial degrees of freedom. We furthermore suggest that the sacculocollic reflex plays an important role in maintaining the relative position of the head and the body against the vertical linear acceleration of gravity.

Afferent Pathways↗
PubMed1986

Sinusoidal galvanic stimulation of the labyrinths and postural responses.

We studied the effect of sinusoidal stimulation of the labyrinths on postural reflexes in man, using a 0.3 Hz current of alternating polarity and +/- 1 mA intensity for stimulation. The test subjects were tested binaurally by the bipolar method (BB), with two electrodes on the mastoid processes, and binaurally by the monopolar method (BM), with electrodes localized bilaterally on the mastoid process and the hand. Stabilographic postural parameters were measured in 22 subjects in five experimental situations. Each situation lasted 60 s. Body sway, detected by astabilometer, was recorded on a Philips FM tape-recorder and then analysed off-line on a PDP-11/34 computer. On BB stimulation of the labyrinths, the variance of body sway in the left-right (LR) direction increased more than in the anteroposterior (AP) direction. In BM stimulation, only the variance of LR sway increased. Other posturographic parameters displayed a similar effect. From the aspect of body sway frequency, BB stimulation produced a peak in the course of the power spectral density of the lateral stabilogram at 0.3 Hz. In this experimental situation, a habituation effect was manifested, depending on the subject. It can be stated that binaural bipolar (BB) stimulation of the labyrinths selectively influences lateral body sway, while the increase in AP body sway in this situation is merely a concomitant phenomenon.

Adult↗
PubMed1996

Neurobehavioral consequences of induced spreading depression following photothrombotic middle cerebral artery occlusion.

In a model of experimental focal cerebral ischemia, we have recently reported a strong correlation between the magnitude of ischemic depolarizations in the peri-infarct borderzone and the extent of histological injury. In the present study, we assessed the neurobehavioral consequences of spontaneously occurring and induced ischemic depolarizations in rats following middle cerebral artery (MCA) occlusion, as well as the effects of induced spreading depression (SD) in intact animals. Halothane-anesthetized, artificially ventilated Sprague-Dawley rats underwent photothrombotic MCA occlusion coupled with ipsilateral common carotid artery (CCA) occlusion. The electroencephalogram and direct current (DC) potential were recorded in the parietal infarct borderzone-corresponding to the cortical forelimb area-for 3 h following MCA occlusion. Group 1 rats (n = 9) received MCA/CCA occlusion, and the spontaneously occurring negative DC shifts were recorded in the ischemic borderzone. In Group 2 animals (n = 9), the (non-ischemic) frontal pole of the ipsilateral hemisphere was electrically stimulated in order to double the frequency of peri-infarct DC shifts occurring over the initial 3 h postocclusion. Group 3 consisted of intact rats (n = 3) in which SD was repeatedly evoked in the frontal pole. Four animals served as sham-operated controls. A battery of sensorimotor behavioral tests, consisting of beam balance, postural reflex and elicited forelimb placing, was applied in a blinded fashion. Sham controls and animals of Groups 1 and 2 were tested 24 h after surgery, and Group 3 rats were tested 2, 6 and 24 h after generation of SDs. A cumulative neurobehavioral index, ranging from 0 to 144, was calculated by adding the individual test results. Brains were perfusion-fixed 24 h following surgery for calculation of volumes of infarction and scattered neuronal injury. Functional outcome at 24 h was significantly worse in Group 2 animals (spontaneous plus induced ischemic depolarizations) (neurobehavior index 43 +/- 19, mean +/- S.D.) compared to Group 1 rats, in which only spontaneous depolarizations occurred (neurobehavior index 24 +/- 19, P < 0.05). The cumulative neurobehavioral index of Group 1 and 2 animals correlated positively with the volume of total ischemic injury (r = 0.765, P < 0.001) and with the frequency of ischemic depolarizations (r = 0.474, P < 0.05). Correlations between severe forelimb placing deficits and severe degrees of histological injury (necrosis or ischemic cell change) in the corresponding primary sensorimotor cortical region FR1 were significant in these rats. Group 3 rats showed severe neurobehavioral deficits at 2 and 6 h following SD stimulation (index 57 +/- 1 and 39 +/- 1, respectively) but returned to normal at 24 h (4 +/- 0). The findings indicate that cortical spreading depression is accompanied by transient neurobehavioral deterioration and that SD in the ischemic hemisphere of animals subjected to MCA occlusion worsened functional outcome 24 h after surgery.

Animals↗
PubMed2001

Injury severity and sensitivity to treatment after controlled cortical impact in rats.

We sought to determine sensitivity of the cortical impact injury model of traumatic brain injury (TBI) to severity of injury and to treatment. We examined the pattern of motor and cognitive deficits and recovery following TBI over a range of injury severities, and examined the efficacy of surface-induced moderate hypothermia at three disparate injury levels. In experiment I, Sprague-Dawley rats were injured at one of eight injury severity levels from 0 mm (sham) to 2.5 mm depth of penetration. On postinjury day 1, balance beam, rotorod performance, and posture reflexes were evaluated. Motor outcome was increasingly impaired with increasing injury levels, with the pattern of deficits showing a step-like function. Cognitive deficits, assessed using water maze on day 7, were more severe for the 2.5-mm group than for the 1.6-mm injury group, while the 1.0-mm group did not differ from the sham controls. In experiments II-IV, hypothermia, 30 degrees C for 3-h duration or normothermia was applied to three injury levels: 1.0 mm, the least cortical deformation; 2.5 mm, the most deformation; and 1.6 mm, representing a level in-between. Neurologic outcome was assessed relative to shams on postinjury days 1, 3, and 5. The 1.0-mm group exhibited small deficits that recovered completely by day 3; the 1.6-mm group recovered to the level of shams by day 5, and the 2.5-mm group did not show significant recovery during the testing period. Hypothermia effectively attenuated behavioral deficits for the 1.6-mm group, but had no effect on the other two groups. These three observations--that increasing injury severity is associated with increasing motor and cognitive deficits, that injury severity is related to recovery time, and that hypothermia treatment is selectively effective--have each been reported in the human TBI population; thus, moderate cortical impact injury in rats may be a model with clinical predictability for evaluating neuroprotective therapies.

Animals↗
PubMed1992

Beat-by-beat analysis of cardiac output and blood pressure responses to short-term barostimulation in different body positions.

Rapid quantification of the human baro-reflex control of heart rate has been achieved on a beat-by-beat basis using a neck-chamber with quick ECG-triggered pressure changes. Referring to recent findings on heart rate and stroke volume, the present study uses this technique to compare cardiac output as well as blood pressure changes in supine and upright position to investigate feedback effects and to confirm postural reflex modifications not revealed by RR-interval changes. A suction profile starting at +40 mmHg and running 7 steps of pressure decrease down to -65 mmHg was examined in 0 degree and 90 degrees tilting position while beat-by-beat recordings were done of heart rate, stroke volume (impedance-cardiography) and blood pressure (Finapres (tm)) (n=16). The percentual heart rate decrease failed to be significantly different between positions. A suction-induced stroke volume increase led to a cardiac output almost maintained when supine and significantly increased when upright. A decrease in all blood pressure values was found during suction, except for systolic values in upright position which increased. Conclusively, (a) it is confirmed that different inotropy accounts for the seen gravitational effect on the cardiac output not represented by heart rate (b) identical suction levels in different positions lead to different stimuli at the carotid receptor. This interference has to be considered in microgravity studies by beat-by-beat measurement of cardiac output and blood pressure.

Adult↗
PubMed2000

Plantar grasp reflex in high-risk infants during the first year of life.

For most primitive reflexes, retention of the reflex beyond the period when it should no longer be elicited suggests a pathologic process within the central nervous system. However, for certain primitive reflexes, such as the plantar grasp reflex, a negative response within the first months of life is suggestive of a neurologic abnormality. From the results of one prospective and one retrospective study, it is clearly indicated that the absence of the plantar grasp reflex from 3 months of age and on correlates with the development of spastic cerebral palsy. The specific combination of presence or absence of specific primitive reflexes, postural reactions, or both may accurately predict a specific type of cerebral palsy or neurodevelopmental abnormality.

Age Factors↗
PubMed1990

Microgravity enhances the relative contribution of visually-induced motion sensation.

Visually-induced self-motion sensation and postural reflexes were first explored in microgravity on the Spacelab 1 mission where four subjects demonstrated that visual orientation effects were stronger in microgravity than preflight. Extended testing of two more subjects during the Spacelab D-1 orbital flight confirmed this finding. The development of visual substitution for inappropriate graviceptor information occurs over the first day or two in microgravity. Additional instrumentation to measure postural reactions failed to produce a more reliable indicator of visual effects than subjective orientation. Localized tactile cues applied to the feet changed the qualitative nature of vection and reduced its subjective strength.

Cues↗