Control In Normal Subjects Research Articles

Effect of Rotating Auditory Scene on Postural Control in Normal Subjects, Patients With Bilateral Vestibulopathy, Unilateral, or Bilateral Cochlear Implants.

Objective: The aim of this study was to investigate the impact of a rotating sound stimulation on the postural performances in normal subjects, patients with bilateral vestibulopathy (BVP), unilateral (UCI), and bilateral (BCI) cochlear implantees.Materials and Methods: Sixty-nine adults were included (32 women and 37 men) in a multicenter prospective study. The group included 37 healthy subjects, 10 BVP, 15 UCI, and 7 BCI patients. The average of age was 47 ± 2.0 (range: 23–82). In addition to a complete audiovestibular work up, a dynamic posturography (Multitest Framiral, Grasse) was conducted in silence and with a rotating cocktail party sound delivered by headphone. The center of pressure excursion surface (COPS), sensory preferences, as well as fractal, diffusion, and wavelet analysis of stabilometry were collected.Results: The rotating sound seemed to influenced balance in all subgroups except in controls. COPS increased with sound in the BVP and BCI groups in closed eyes and sway-referenced condition indicating a destabilizing effect while it decreased in UCI in the same condition suggesting stabilization (p < 0.05, linear mixed model corrected for age, n = 69). BVP had higher proprioceptive preferences, BCI had higher vestibular and visual preferences, and UCI had only higher vestibular preferences than controls. Sensory preferences were not altered by rotating sound.Conclusions: The rotating sound destabilized BVP and BCI patients with binaural hearing while it stabilized UCI patients with monaural hearing and no sound rotation effect. This difference suggests that binaural auditory cues are exploited in BCI patients for their balance.

Taping and bracing of the knee joint: a ladder of conservative intervention for patellofemoral pain

Background: Over the last 30 years there has been considerable interest in different conservative treatments for patellofemoral pain. Although a consensus has emerged that low cost treatments such as taping and bracing are effective at relieving pain, there has been an ongoing debate about whether these effects are mediated by enhancing proprioceptive mechanisms. In addition few papers have been published comparing the biomechanical effects of such interventions on knee varus/valgus and internal/external control in normal subjects or subjects who suffer from knee pain and instability. Purpose: The purpose of this work was to explore the biomechanical effects of taping and bracing in healthy individuals and people with patellofemoral pain, and to determine if a “ladder of effectiveness” exists with the different interventions. Methods: Twenty-four patients with patellofemoral pain and thirty-nine healthy individuals were asked to perform a slow step down task. This was conducted under a range of randomised conditions including: (a) no intervention, (b) neutral patella taping, (c) tubigrip, (d) patellofemoral web brace with patellar stabilization and (e) a silicone reinforced compression sleeve. In all cases three dimensional movement and moments at the knee were collected using a ten camera infra-red Qualisys motion analysis system and two AMTI force platforms. Reflective markers were placed on the foot, shank and thigh using the Calibrated Anatomical Systems Technique. Results: An independent samples t-test showed that the patients had a significantly greater knee varus/valgus range of motion than the healthy individuals, 9.5 and 6.5 degrees respectively (p < 0.01) with no intervention. A mixed methods ANOVA identified changes in the knee varus/valgus and internal/external range of motion between the interventions, p = 0.03 and p = 0.01 respectively. The brace with patellar stabilization reduced knee varus/valgus and internal/external range of motion by 2.8 degrees (p < 0.01), followed by the textured neoprene sleeve and tubigrip which reduced the knee varus/valgus range of motion by 2.7 degrees (p < 0.05), with the neutral taping showing a 1.3 degree reduction in the patient group only (p < 0.05). No differences were seen in peak knee flexion. At the end of the test the participants were asked to place the conditions in a rank order of which they thought helped most with joint stability and pain. The most popular order was the web brace with patellar stabilization or silicone reinforced compression sleeve, neutral tape or tubigrip and then no intervention. Conclusion(s): These changes in knee mechanics provide important evidence about the possible proprioceptive and mechanoreceptive effects of such treatments, and their role in the management of individuals with patellofemoral pain. This reinforces the view that varus/valgus and internal/external mechanics should not be overlooked when studying knee pain and instability. Implications: This work provides evidence for a graduated ladder of intervention, from neutral taping which produced a small improvement in varus/valgus control, tubigrip and textured neoprene sleeves giving a further improvements varus/valgus control and bracing producing the greatest improvement in varus/valgus and internal/external control. These results fit well with participants’ perceptions of which they thought helped most with joint stability and pain level.

Effect of redesigned Indian mixed meals on blood glucose and insulin levels in normal versus type 2 diabetic subjects–a comparative study

This study reports the glycemic as well as insulinemic response of seven types of Indian vegetarian mixed meals (MMs). Each of the seven MMs was given at weekly intervals to both normal and type 2 diabetic subjects on the same day to reduce variations in food preparations. In this Indian study, each MM consisted of five to six food items with a low glycemic index (GI) ranging from 28.98 to 46.12%, glycemic load ranging from 15.58 to 23.8 g and energy value (calculated) from each test meal ranging from 403 to 502 kcal. All the seven meals were found to have postprandial glycemic control in normal subjects which ranged from 86 to 102.4 mg%, and a good postprandial glycemic control in type 2 diabetic subjects which ranged from 132.8 to 148.4 mg%, and hence appropriate for routine consumption by diabetic subjects. The glycemic and insulinemic pattern of all these MMs was similar in normal and diabetic subjects. Sustained intake of such low GI MMs by diabetic can result in good glycemic control.

The effect of repeated visual motion stimuli on visual dependence and postural control in normal subjects

Patients with vestibular dysfunction, migraine and/or anxiety may experience visual vertigo (VV), whereby symptoms are provoked by disorienting visual environments (e.g. supermarkets). Patients with VV over rely on vision for balance (i.e. visually dependent). Visual vertigo significantly improves when vestibular rehabilitation incorporates exposure to optokinetic stimulation (OKS). However, whether OKS exposure induces a reduction in visual dependency is unknown. This study investigated this issue by measuring visual dependency before and after repeated OKS exposure. Twenty-six healthy subjects (10 males; mean age 29.8 years, range 20–42 years) were randomly allocated into an OKS group who underwent graded OKS exposure for five consecutive days, or a no intervention control group. Assessment included the ‘Rod and Frame’ and ‘Rod and Disc’ tests where subjects set the subjective visual vertical in darkness, facing a tilted luminous frame or luminous rotating disc, respectively. Postural sway measures were obtained with eyes open, closed and facing the rotating disc. Results showed significant reductions in subjective vertical tilt with the frame and rotating disc for the OKS group only (p≤0.01). Total sway path and mean deviation induced by the rotating stimulus decreased significantly only for the OKS group (p<0.01), as did the Kinetic Quotient (disc rotation/eyes open sway path ratio; p=0.04). The Romberg Quotient (eyes closed/eyes open ratio) showed no change. Findings suggest visual dependency, both at a perceptual and a postural level, can be reduced with short-term graded OKS exposure in healthy subjects. This has important implications for treatment of patients with VV and balance disorders.

The pathogenic role of rheumatoid factor in rheumatoid arthritis

Rheumatoid factors (RFs) are the first autoantibodies described in rheumatoid arthritis (RA), which target the Fc region of IgG. Since their discovery, RFs have been the subject of extensive studies not just because of their association with RA, but also because they serve as an excellent model for the regulation and induction of disease-related autoantibodies. Although RFs are normally induced during secondary immune responses, isotype switching and affinity maturation are confined to RA patients and are not observed in normal individuals. Therefore, the emergence of high-affinity RFs, which are believed to depend on T-cell help, is under strict control in normal subjects, whereas these control mechanisms appear to be bypassed in RA. In this article, we provide an overview of the current knowledge of how pathologic RFs are induced and discuss the mechanisms by which RFs contribute to RA disease process.

Effects of the cold pressor test on cardiac autonomic control in normal subjects

The cold pressor test (CPT) triggers in healthy subjects a vascular sympathetic activation and an increase in blood pressure. The heart rate (HR) response to this test is less well defined, with a high inter-individual variability. We used traditional spectral analysis together with the non-linear detrended fluctuation analysis to study the autonomic control of HR during a 3-min CPT. 39 healthy young subjects (23.7+/-3.2 years, height 180.4+/-4.7 cm and weight 73.3+/-6.4 kg) were divided into two groups according to their HR responses to CPT. Twenty subjects have a sustained increase in HR throughout the test with reciprocal autonomic interaction, i.e. increase in sympathetic activity and decrease vagal outflow. In the 19 remainders, HR decreased after an initial increase, with indication of involvement of both sympathetic and vagal outflow. Baseline evaluation of the subjects revealed no difference between the two groups. Nevertheless, a higher sympathetic activity at the skin level during CPT was present in the group with decreased HR. Further studies are needed to explain why healthy subjects react differently to the CPT and if this has potential clinical implications.

Control of prepotent responses by the superior medial frontal cortex

The inhibitory control of prepotent action is vital for appropriate behaviour. An example of the importance of such control can be seen in the inhibition of aggressive behavior, deficits in which may have broader consequences for society. Many studies have related lesions or the under-development of the prefrontal cortex to inefficiency of inhibitory control. Here we used transcranial magnetic stimulation and a stop-signal task, which occasionally requires the inhibition of a prepotent motor response, to investigate the role of pre-supplementary motor area (Pre-SMA) in inhibitory control. While no effects were seen on the ability to generate responses, TMS delivered over the Pre-SMA disrupted the ability to respond to a stop signal. These results are the first to establish a casual link between Pre-SMA and inhibitory control in normal subjects. The understanding of the underlying mechanisms of inhibitory control may lead to clearer understanding of the neural basis of inappropriate behaviour.

Posthypoxic ventilatory decline during NREM sleep: influence of sleep apnea.

We wished to determine the severity of posthypoxic ventilatory decline in patients with sleep apnea relative to normal subjects during sleep. We studied 11 men with sleep apnea/hypopnea syndrome and 11 normal men during non-rapid eye movement sleep. We measured EEG, electrooculogram, arterial O(2) saturation, and end-tidal P(CO2). To maintain upper airway patency in patients with sleep apnea, nasal continuous positive pressure was applied at a level sufficient to eliminate apneas and hypopneas. We compared the prehypoxic control (C) with posthypoxic recovery breaths. Nadir minute ventilation in normal subjects was 6.3 +/- 0.5 l/min (83.8 +/- 5.7% of room air control) vs. 6.7 +/- 0.9 l/min, 69.1 +/- 8.5% of room air control in obstructive sleep apnea (OSA) patients; nadir minute ventilation (% of control) was lower in patients with OSA relative to normal subjects (P < 0.05). Nadir tidal volume was 0.55 +/- 0.05 liter (80.0 +/- 6.6% of room air control) in OSA patients vs. 0.42 +/- 0.03 liter, 86.5 +/- 5.2% of room air control in normal subjects. In addition, prolongation of expiratory time (Te) occurred in the recovery period. There was a significant difference in Te prolongation between normal subjects (2.61 +/- 0.3 s, 120 +/- 11.2% of C) and OSA patients (5.6 +/- 1.5 s, 292 +/- 127.6% of C) (P < 0.006). In conclusion, 1) posthypoxic ventilatory decline occurred after termination of hypocapnic hypoxia in normal subjects and patients with sleep apnea and manifested as decreased tidal volume and prolongation of Te; and 2) posthypoxic ventilatory prolongation of Te was more pronounced in patients with sleep apnea relative to normal subjects.

After-effects of visuo-manual adaptation to prisms on body posture in normal subjects.

Postural equilibrium is known to be controlled by sensorimotor reflexes and automatic control loops but also depends on high-level body representation in space, probably implicating the right temporoparietal cortex. Indeed, short-term prism adaptation to a 10 degrees rightward visual shift has been shown to reduce predominant postural imbalance in patients with right hemisphere damage, as it did for neglect symptoms. These effects are likely to be explained by a high level effect of prism adaptation on body and space representation, rather than by a sensorimotor effect. Cognitive after-effects of prism adaptation to a leftward visual shift, suggesting neglect-like symptoms, have also recently been shown in normal subjects on line bisection tasks. In the present study, we investigated the effect of wedge prism adaptation on postural control in normal subjects. Two groups of seven healthy subjects were either adapted to a leftward or a rightward visual shift. Results showed that our procedure induced changes in lateral postural control in normal subjects. Furthermore, this lateral postural after-effect was dependent on direction of prism adaptation. Indeed, only adaptation to a leftward visual shift induced significant rightward postural bias in normal subjects. The rightward postural lateral displacement was negatively correlated with the visual vertical. Both transfer and direction specific effect of visuo-manual adaptation to prisms on postural control suggest that effects of adaptation act more on high-level postural control linked to body representation in space or at least reveal close interaction between sensorimotor plasticity and body representation.

The complex role of spindle afferent input, as evidenced by the study of posture control in normal subjects and patients

This report reviews recent findings from our laboratory on the connectivity of the group II spindle afferent input and the role played by these afferents in the control of quiet and perturbed human stance. At variance with group Ia fibres, which subserve the monosynaptic stretch reflex, the group II fibres, after having entered the spinal cord, make synamptic contacts with a short chain of interneurons which impinge on homonymous motoneurons. Analysis of the short- and medium-latency responses evoked in foot and leg muscles by perturbations of upright stance under different experimental conditions has revealed a role of group II fibres in the production of the medium-latency response. The conduction velocity of group II spindle afferent fibres and their central delay have also been estimated. Furthermore, data from normal subjects and from neuropathic and hemiparetic patients are in favour of a prevailing role of the input from group II fibres in the afferent control of quiet and perturbed stance. Since Ia fibres innervate receptors more sensitive to the veolocity of muscle stretch, and II fibres innervate receptors more sensitive to the absolute value of muscle length, it is hypothesised that the major role of the latter in the reflex control of stance reflects the slow velocity and amplitude of sway during quiet upright posture. Indirect evidence supports the conclusion that, also in humans, monoaminergic descending pathways from brainstem nuclei modulate the excitability of the circuits mediating the group II input.

The role of ocular oscillations upon visually dependent postural stabilization in patients affected by congenital nystagmus

Visually dependent postural stabilization decreases as a consequence of a long-standing reduction of visual cues in patients affected by congenital nystagmus. The aim of the present study was to verify whether the changes in postural control in this group of patients are due to ocular oscillations or to reduced visual acuity. Therefore, postural control was evaluated when the nystagmus was blocked by the blocking position or by prisms and compared with the postural score observed in a group of normal controls whose visual acuity had been artificially reduced to the same level as that of the patients using Bangerter's filters. The results show a statistically significant improvement of visually dependent postural stabilization when ocular oscillations are inhibited either by the gaze blocking position or by prisms. They also show that postural control in normal subjects with Bangerter's filters is reduced, but is still significantly better than that observed when ocular oscillations are inhibited in patients affected by congenital nystagmus. Our data strongly support the role of ocular oscillations in visually dependent postural control, since postural impairment recovered under any condition in which ocular oscillations were abolished, despite differences in visual acuity. Our data also show that reduced visual acuity decreases visually dependent postural control to a lesser degree than ocular oscillations. This could be due to the fact that ocular oscillations are a disturbing input, usually inhibited centrally, in order to avoid oscillopsia. This mechanism is probably responsible for the reduced role of visual cues in the postural control in this group of patients. The reduction of visual acuity, by comparison, merely causes a decrease in visual cues, depending on the degree of visual loss. It can be concluded that the impaired postural control in patients affected by congenital nystagmus is mainly due to ocular oscillations, with reduced visual acuity creating a secondary effect.

Learned control of slow potential interhemispheric asymmetry in schizophrenia

We report on the feasibility of teaching 16 (DSM-IV) schizophrenic patients, subdivided by syndrome, self-regulation of interhemispheric asymmetry having demonstrated efficient learning of interhemispheric control in normal subjects. Reversal of asymmetry may be important to treatment and recovery in schizophrenia for following improvement on neuroleptic drugs functional hemispheric asymmetries have reversed, with directions of reversal and pre-existing asymmetry dependent on syndrome. Asymmetry reversal in animals, manifested by spatial turning tendencies, has been used as a marker of neuroleptic action and involves striatal dopamine under reciprocal hemispheric control. We gave as feedback the left–right asymmetry in slow potential negativity recorded from the sensory motor strip (C3,4). Feedback took the form of a rocket on a screen which rose or fell with leftward or rightward shifts in negativity. Patients were able to learn control ( P<0.01). In those patients with lesser ability this was due to inability to sustain concentration throughout the session rather than slow initial learning. Active syndrome patients were better able to shift negativity rightward and withdrawn patients leftward, directions associated with drug reversal of functional asymmetry and symptom recovery for each syndrome. Accordingly our demonstration that many symptomatic schizophrenic patients are capable of learning control opens the door to electrocortical operant conditioning training in schizophrenia with therapeutic regimens.

The effects of lidocaine on cardiac parasympathetic control in normal subjects and in subjects after myocardial infarction.

It has been widely accepted that lidocaine has little or no effect on the autonomic nervous system. However, we have previously shown that in dogs with vagally induced atrial fibrillation, lidocaine has a pronounced parasympatholytic effect. To study the possible effect of lidocaine on autonomic cardiac control in humans, we performed spectral analysis of heart rate fluctuations in 19 healthy volunteers, who received an i.v. bolus of lidocaine (1.4 mg/kg), as well as in 13 patients suffering from acute inferior myocardial infarction (IMI) and 13 patients suffering from acute anterior myocardial infarction (AMI), who received therapeutic doses of i.v. lidocaine infusion (4 mg/min). Heart rate variability and respiratory pattern were monitored according to a predetermined protocol, with and without lidocaine. Computing the heart rate power spectrum and integrating over predetermined frequency bands, we focused mainly on the respiratory frequency band, known to predominantly reflect parasympathetic control. The administration of lidocaine resulted in a significant overall increase in mean heart rate: for the healthy control group an increase of 5.5 +/- 2.2% (mean +/- SE), for the IMI group an increase of 9.4 +/- 3.5%, and for the AMI group an increase of 8.1 +/- 2.9% (p < 0.01 for all). Simultaneously, following the administration of lidocaine, there was a decrease in the power of respiratory fluctuations: for the healthy control group a decrease of 38.4 +/- 12.5%, for the IMI group a decrease of 46.3 +/- 32.9%, and for the AMI group a decrease of 33.9 +/- 16.2% (p < 0.01 for all). These findings indicate that lidocaine has a consistent and significant parasympatholytic effect on the human heart, in healthy volunteers as well as in patients in the acute phase of myocardial infarction.

Orofacial and finger force control in normal subjects

The relationship among several parameters of the ramp-and-hold force contraction and target force level was quantified for the upper lip, lower lip, and tongue on the one hand, and right and left index on the other hand, in 12 normal subjects (6 males and 6 females). Using visual feedback, subjects produced ramp-and-hold compression lip, tongue, and index forces as rapidly and accurately as possible to end-point target levels ranging from 0.25 to 2 newtons, these fine force occurring within physiologic levels presumably involved in speech production. Given the special anatomic and physiologic characteristics of the orofacial system, the purpose of this study was to compare lip, tongue, and finger force control in order to determine whether the motor control is uniform in both systems, that of the speech production and that of the limb, and within subsystems of speech production. Consequently, can be pathophysiology of a movement disorder in its stereotypic form be considered across limb and speech systems? It seems likely that measures of orofacial force control provide useful insights into the fundamental motor control problem of any individual with dysarthria.

Differences in circulatory control in normal subjects who faint and who do not faint during orthostatic stress.

We have determined if there are differences in normal subjects who fainted and those who did not faint during prolonged standing. We studied the short-term orthostatic responses in relation to heart rate, blood pressure measured by Finapres, left ventricular stroke volume analysed by pulse contour method, cardiac output and systemic vascular resistance, and also postural blood pressure and heart rate variability as assessed by spectral analysis. Thirteen healthy males without a history of syncope were studied. Three fainted after 10-13 min standing; the ten non-fainters remained upright for 20 min. The initial (first 30 s) postural circulatory adjustment was comparable for blood pressure but the rebound bradycardia was smaller in the fainters (heart rate at 22 s amounted to +13 +/- 10 beats/min above control vs. +1 +/- 5 beats/min in the non-fainters). Upright heart rate at 2 min standing was higher in the fainters (+31 +/- 2 beats/min vs. +20 +/- 5 beats/min), and blood pressure at 7 min standing was lower (-2/+5/+8 +/- 5/5/5 mmHg vs. +11/+13/+16 +/- 10/6/5 mmHg). The responses of stroke volume and cardiac output were comparable but systemic vascular resistance gradually decreased in the fainters from 5 min standing to the onset of fainting (+4 +/- 13% vs. +33 +/- 19% at 7 min standing). In fainters, the variability in upright blood pressure around 0.1 Hz was larger (8.8 mmHg2/Hz for diastolic blood pressure vs. 5.7 +/- 1.5 mmHg2/Hz in non-fainters).(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of proprioception to posture control in normal subjects.

In order to investigate the contribution of proprioceptive input to maintaining an upright position, stabilometry via 100-Hz vibratory stimulation applied to the Achilles tendon was studied and analyzed with respect to area, length and power spectra according to the method of fast Fourier transform (FFT). Twenty-one young medical students were analyzed in this study. When vibration was applied, the body sway was significantly greater than that of control in area and length with both eyes open and closed. There was a significant increase of total power in both the lateral (X) and antero-posterior (Y) directions with the eyes closed. With the eyes open, an increase was found only in the antero-posterior direction. The frequency band indicating the maximum spectrum did not shift. Significant increases in power spectra were found in the frequency range of more than 2 Hz in both two directions with the eyes closed. It was concluded that a vibration given to the Achilles tendon provoked a pronounced high frequency body sway especially in the antero-posterior direction when visual information was nullified, and that proprioceptive information may have a minor role compared with visual information.

A sensitive assay of transthyretin (prealbumin) in human cerebrospinal fluid in nanogram amounts by ELISA

A sensitive ELISA method for determining transthyretin (prealbumin) in human cerebrospinal fluid (CSF) is described. The method utilizes goat antihuman transthyretin antibody (IgG fraction) for capture and peroxidase conjugated antibody for color development. The assay has a linear range of 1–4 ng transthyretin added per well. The within-day and between-day coefficients of variation are 5.1 and 6.1%, respectively. The concentration of transthyretin in CSF (ranging from 5 to 20 mg per L) correlated significantly with the corresponding serum concentrations (range 170–420 mg/l). This suggests that synthesis of transthyretin in the brain and peripheral tissues is under similar biological control in normal subjects. The transthyretin concentrations in CSF did not correlate with total CSF protein concentration or age of the subject.

Quantitation of skin vasomotor control in normal subjects and in diabetic patients with autonomic neuropathy

Peripheral autonomic neuropathy in diabetes has been difficult to evaluate. We have developed a test to quantitate sympathetic skin vasomotor function in the extremities. Skin vasomotor reflexes were investigated after warming and cooling the left arm and recording changes in skin temperature as a measure of skin blood flow in the right hand and both feet. Twenty-three diabetic patients with cardiac autonomic neuropathy and 28 healthy control subjects were examined. In contrast to the healthy subjects, the diabetic patients showed reduced or even absent responses in skin temperature to both warming and cooling. The rate of skin temperature decrease for the hand and feet during cooling, which was used as the actual parameter to quantitate skin vasomotor control, was significantly reduced in the diabetic group as compared with the healthy control subjects. We conclude that this technique provides a simple non-invasive method for quantitating skin vasomotor function in the extremities of diabetic patients.

Effects of Diazepam and Chlormethiazole on Ventilatory Control in Normal Subjects

Effects of Diazepam and Chlormethiazole on Ventilatory Control in Normal Subjects