Stable Deficits Research Articles

Shared and distinct oculomotor function deficits in schizophrenia and obsessive compulsive disorder.

Detailed analysis of oculomotor function phenotypes in antisaccade, smooth eye pursuit, and active fixation tasks was performed in a sample of 44 patients with schizophrenia, 34 patients with obsessive compulsive disorder (OCD), and 45 matched healthy controls. A common pattern of performance deficits in both schizophrenia and OCD emerged including higher antisaccade error rate, increased latency for corrective antisaccades, as well as higher rates of unwanted saccades in smooth eye pursuit compared to healthy controls. This common pattern could be related to the dysfunction of a network of cognitive control that is present in both disorders, including the dorsolateral prefrontal cortex, the posterior parietal cortex, and the anterior cingulate cortex. In contrast, only patients with schizophrenia showed a specific increase for correct antisaccade mean latency and the intrasubject variability of latency for error prosaccades as well as a decrease in the gain for smooth eye pursuit, suggesting a specific deficit in saccadic motor control and the frontal eye field in schizophrenia that is not present in OCD. A specific deficit in fixation stability (increased frequency of unwanted saccades during active fixation) was observed only for OCD patients pointing to a deficit in the frontostriatal network controlling fixation. This deficit was pronounced for OCD patients receiving additional antipsychotic medication. In conclusion, oculomotor function showed shared and distinct patterns of deviance for schizophrenia and OCD pointing toward shared and specific neurobiological substrates for these psychiatric disorders.

Gross motor skills are related to postural stability and age in children with autism spectrum disorder

Motor skill and postural stability deficits are commonly reported for children with autism spectrum disorder (ASD), however the relationship between these variables is not well established. We explored the relationship between motor skills, postural stability, restricted and repetitive patterns of behavior, diagnosis, age, and sex. Children (11 with and 11 without ASD), 5–12 years of age, participated in the study. The Test of Gross Motor Development-3 (TGMD-3) was used to assess fundamental motor skills. Postural sway was measured on a force plate during quiet standing on a solid and compliant surface. Center of pressure was calculated and used to compute sway area. Linear regression analysis showed that sway area on a solid surface, age, and diagnosis were significant predictors of motor skill performance (R2=.854). Severity of ASD, as assessed by the Repetitive Behavior Scale-Revised (RBS-R), was not predictive of motor skills. Children with ASD exhibited deficits in postural stability compared to children without ASD. Postural stability appears to influence the ability of children to perform gross motor skills. However, the RBS-R does not seem to be a useful tool for identifying those children with ASD who exhibit the greatest deficits in motor skills.

The production structure, exchange rate preferences and the short-run—Medium-run macrodynamics

This paper focuses on the role of the production structure in shaping output shares, wage bargaining and the dynamics of the real exchange rate in a Neo-Kaleckian macroeconomic model. While changes in the rate of capital utilization ensure the short-run equilibrium, in the medium run the real exchange rate must adjust to stabilize the labor market and the external sector. Interestingly, these variables define a trilemma in which it is not possible for workers to have their desired wage share, for firms to have their desired profit share in output and for the economy to have a stable deficit in current account to GDP ratio at the same time. Structural change allows for a way out of the trilemma as it makes possible a higher wage share for a given profit share with external equilibrium. The corollary is that distribution and high employment cannot be sustained solely by conventional fiscal and monetary policies: they also require industrial and technological policies that redefine the structural parameters of the system, as a form of reconciling conflicting claims with external equilibrium.

Motion Analysis and the Anterior Cruciate Ligament: Classification of Injury Risk

Anterior cruciate ligament (ACL) injuries are common, catastrophic events that incur large expense and lead to degradation of the knee. As such, various motion capture techniques have been applied to identify athletes who are at increased risk for suffering ACL injuries. The objective of this clinical commentary was to synthesize information related to how motion capture analyses contribute to the identification of risk factors that may predict relative injury risk within a population. Individuals employ both active and passive mechanisms to constrain knee joint articulation during motion. There is strong evidence to indicate that athletes who consistently classify as high-risk loaders during landing suffer from combined joint stability deficits in both the active and passive knee restraints. Implementation of prophylactic neuromuscular interventions and biofeedback can effectively compensate for some of the deficiencies that result from poor control of the active knee stabilizers and reduce the incidence of ACL injuries.

Individuals with both perceived ankle instability and mechanical laxity demonstrate dynamic postural stability deficits

BackgroundChronic ankle instability is a frequent and serious consequence of lateral ankle sprains. The contribution of perceived instability and potential for mechanical laxity to contribute to the overall deficit in dynamic postural stability is unclear. The purpose was to determine if those with mechanical laxity demonstrated significant differences in dynamic postural stability compared to controls, copers and those with perceived instability. MethodsOf 93 participants, 83 recreationally active individuals were divided into 4 groups: controls, copers, those with perceived instability, and those with both perceived instability and mechanical laxity. Injury history and the Cumberland Ankle Instability Tool were collected, and an instrumented arthrometer was applied. Participants completed a single limb jump landing, balancing upon completion. Ground reaction force data were collected, scaled to body mass, and the Dynamic Postural Stability Indices were calculated for anterior–posterior, medial–lateral, vertical and composite. One-way ANOVAs with Tukey post-hoc tests (α<0.05) were conducted on each of the stability indices among the four groups. FindingsThe mechanically lax group had significantly greater mean (standard deviation) medial–lateral stability index scores 0.57 (0.62) than the coper group 0.24 (0.20; P=0.02) and significantly greater composite index scores 0.73 (0.57) than the perceived instability 0.49 (0.09) and coper groups 0.47 (0.12 P=0.05). No other indices were significantly different among groups. InterpretationIndividuals with perceived instability and mechanical laxity exhibited dynamic postural deficits compared to copers and those with perceived instability alone. Mechanical laxity may contribute to the deficits in dynamic postural stability.

Effect Of Exercise-induced Fatigue On Lower-extremity Emg Amplitude During A Maximum Vertical Forward-lateral Jump

Muscular fatigue during exercise alters neuromuscular function. Exercise-induced muscle fatigue is thought to be a potential risk factor for athletic injuries. Few studies have examined the effects of functional exercise-induced fatigue on electromyography (EMG) amplitude (amp) during a highly demanding movement. PURPOSE: To examine EMG amp during a maximum vertical forward-lateral jump, pre and post fatigue. METHODS: Twenty-five asymptomatic subjects (24 ± 2.5 yrs, 175 ± 11 cm, 70 ± 13 kg) were recruited. EMG electrodes were placed over gluteus maximus (GX), gluteus medius (GM), vastus lateralis (VL), and medial hamstring (MH). A maximum vertical jump height (MVJH) was obtained as a baseline. A functional exercise fatigue protocol included 5-min of incremental running, 20-sec of lateral jumps, and 20 vertical lunge jumps. Subjects repeated this cycle until subjects’ RPE scale reached 17 (very hard) and the MVJH fell below 80% of their baseline. Prior to and after the fatigue protocol, subjects performed 5 maximum vertical forward-lateral jumps. Functional linear models were used to compare EMG amp mean difference before and after fatigue. Pairwise comparison functions with 95% confidence intervals (CIs) were plotted to determine significant mean difference. If the curve differences with CIs did not cross zero, then differences existed. RESULTS: Figure 1. After fatigue, GX EMG amp reduced at 0-4%, 38-53%, and 80-97% of stance. GM EMG amp reduced at 84-100% of stance. VL EMG amp reduced at 87-100% of stance. MH EMG amp reduced at 2-6%, 24-61%, and 78-100% of stance. CONCLUSIONS: A reduction in observed EMG amp may be related to movement and dynamic stability deficits of the lower-extremity. More data are needed to examine how these deficits increase an injury incidence.

Validity of the clinical hop test to detect dynamic postural stability deficits

Validity of the clinical hop test to detect dynamic postural stability deficits

Decreased postural control in adolescents born with extremely low birth weight.

The survival rates of infants born preterm with extremely low birth weight (ELBW ≤ 1000 g) have gradually improved over the last decades. However, these infants risk to sustain long-term disorders related to poor neurodevelopment. The objective was to determine whether adolescents born with ELBW have decreased postural control and stability adaptation. Twenty-nine ELBW subjects performed posturography with eyes open and closed under unperturbed and perturbed standing by repeated calf vibration. Their results were compared with twenty-one age- and gender-matched controls born after full-term pregnancy. The ELBW group had significantly decreased stability compared with controls in anteroposterior direction, both during the easier quiet stance posturography (p = 0.007) and during balance perturbations (p = 0.007). The ELBW group had similar stability decrease in lateral direction during balance perturbations (p = 0.013). Statistically, the stability decreases were similar with eyes closed and open, but proportionally larger with eyes open in both directions. Both groups manifested significant adaptation (p ≤ 0.023) to the balance perturbations in anteroposterior direction, though this adaptation process could not compensate for the general stability deficits caused by ELBW on postural control. Hence, adolescent survivors of ELBW commonly suffer long-term deficits in postural control, manifested as use of substantially more recorded energy on performing stability regulating high-frequency movements and declined stability with closed and open eyes both in anteroposterior and lateral direction. The determined relationship between premature birth and long-term functional deficits advocates that interventions should be developed to provide preventive care in neonatal care units and later on in life.

Postural stability deficits during the transition from double-leg stance to single-leg stance in anterior cruciate ligament reconstructed subjects

The goal of this study was to evaluate postural stability during the transition from double-leg stance (DLS) to single-leg stance (SLS) in anterior cruciate ligament reconstructed (ACLR) (n=20) and non-injured control subjects (n=20). All ACLR subjects had fully returned to their pre-injury sport participation. Both groups were similar for age, gender, height, weight, body mass index and activity level. Spatiotemporal center of pressure outcomes of both legs of each subject were measured during the transition from DLS to SLS in eyes open and eyes closed conditions. Movement speed was standardized. The center of pressure displacement after a new stability point was reached during the SLS phase was significantly increased in the ACLR group compared to the control group in the eyes closed condition (P=.001). No significant different postural stability outcomes were found between the operated and non-operated legs. In conclusion, the ACLR group showed postural stability deficits, indicating that these persons may have a decreased ability to stabilize their body after the internal postural perturbation created by the transition from DLS to SLS. The non-operated leg may not be the best reference when evaluating postural stability of the operated leg after ACLR, as no differences were found between legs.

Postural stability during the transition from double-leg stance to single-leg stance in anterior cruciate ligament injured subjects

BackgroundAn anterior cruciate ligament injury may lead to deteriorations in postural stability. The goal of this study was to evaluate postural stability during the transition from double-leg stance to single-leg stance of both legs in anterior cruciate ligament injured subjects and non-injured control subjects with a standardized methodology. MethodsFifteen control subjects and 15 anterior cruciate ligament injured subjects (time after injury: mean (SD)=1.4 (0.7) months) participated in the study. Both groups were similar for age, gender, height, weight and body mass index. Spatiotemporal center of pressure outcomes of both legs of each subject were measured during the transition from double-leg stance to single-leg stance in eyes open and eyes closed conditions. Movement speed was standardized. FindingsThe center of pressure displacement after a new stability point was reached during the single-leg stance phase was significantly increased in the anterior cruciate ligament injured group compared to the control group in the eyes closed condition (P<.001). No significant different postural stability outcomes were found between both legs within both groups (P>.05). No significant differences were found during the transition itself (P>.05). InterpretationThe anterior cruciate ligament injured group showed postural stability deficits during the single-leg stance phase compared to the non-injured control group in the eyes closed condition. Using the non-injured leg as a normal reference when evaluating postural stability of the injured leg may lead to misinterpretations, as no significant differences were found between the injured and non-injured leg of the anterior cruciate ligament injured group.

Reliability and validity of an accelerometry based measure of static and dynamic postural stability in healthy and active individuals

Postural stability is an important measure in both research and clinical practice. A portable, easy to use device that can provide higher resolution than current clinical tests may allow for better identification of patients or athletes with postural stability deficits. The purpose of this study was to evaluate the ability of a tri-axial accelerometer to quantify postural stability in a healthy athletic population. Ten subjects were recruited to determine the reliability of the accelerometer to measure dynamic postural stability and thirteen were recruited to compare the accelerometer measures across tasks of varying difficulty. Subjects were asked to complete four static postural stability tasks with eyes open and eyes closed and two dynamic postural stability tasks for a total of ten tasks. During each task postural stability was measured using a tri-axial accelerometer and force platform. Differences between postural stability scores between tasks and the correlation between the two measures were assessed. The accelerometer demonstrated moderate to good test–retest reliability (ICC=0.732 to 0.899). Only the medial–lateral axis of the accelerometer showed significant differences between static tasks but all directions were able to show significant differences between static and dynamic tasks. Additionally, Spearman's ranked correlations showed little to no correlation between the accelerometer and force platform scores. Accelerometers are a reliability tool for postural stability that measure low difficulty tasks best in the medial–lateral direction. Low correlation between the accelerometer and force platform suggest that these two methods are not measuring the same components of postural stability.

Auditory verbal hallucinations reflect stable auditory attention deficits: a prospective study

Introduction. Previous studies have shown that auditory verbal hallucinations (AVHs) in psychosis are associated with reduced verbal auditory attention. Whether this is an effect of ongoing AVH or reflects a more stable cognitive vulnerability also present after treating the AVH is unknown. The aim of this study was to follow patients with acute psychosis with and without AVH, and to test their auditory attention in a more stabilised clinical phase.Methods. Fifty patients (35 males and 15 females) were examined when admitted to an acute psychiatry ward and tested three months later with a dichotic listening test with attention instructions. The patients were divided into a frequent (n = 33) and non-frequent (n = 17) AVH group based on their score on the Positive and Negative Syndrome Scale item hallucinatory behaviour (≥4 and ≤3, respectively) at baseline.Results. A significant interaction emerged between AVH group and attention instruction condition; the frequent AVH group failed to control their auditory attention as opposed to the non-frequent AVH group.Conclusions. Patients with frequent AVH in an acute psychotic state showed impaired auditory attention three months after their AVH had been treated, indicating a stable cognitive vulnerability factor for experiencing AVH.

Core Stabilization Training After Anterior Cruciate Ligament Reconstruction

Objectives:The aim of this study was to compare the effects of core stabilization exercises and conventional rehabilitation exercises after anterior cruciate ligament reconstruction in terms of knee joint laxity, knee muscle strength, postural stability and functional tests.Methods:Twenty eight patients reconstructed with hamstring tendon were included. Thirteen patients evaluated after a conventional rehabilitation and fifteen after a core stabilization programme. Single-limb postural stability assessment, isokinetic knee muscle strength test, instrumented ligament laxity test, functional hop tests were done to both groups after 16th week. Single-limb postural stability was assessed with stabilometer in both eyes open and eyes-closed conditions. Healthy legs were evaluated as internal controls.Results:Knee flexor and extensor strength indices were not different between groups (p>.05). H/Q strength ratio was different at 180 °/s (p<.05). Knee laxity was not different between groups (p<.05). There was no significant difference in hop distance and hop index between groups (p>.05). Conventional training group had deficit in overall stability score in eyes closed condition (p>.05), but core stabilization group did not have any postural stability deficit (p>.05).Conclusion:Better H/Q strength ratio was seen in core stabilization group. Core stabilization exercises improved postural stability more than classic rehabilitation.

A two-sided estimate for the Gaussian noise stability deficit

The Gaussian noise-stability of a set A in R^n is defined by S_rho(A) = P (X in A and Y in A) where X and Y are standard Gaussian vectors whose correlation is rho. Borell's inequality states that for all 0 < rho < 1, among all sets A with a given Gaussian measure, the quantity S_rho(A) is maximized when A is a half-space. We give a novel short proof of this fact, based on stochastic calculus. Moreover, we prove an almost tight, two-sided, dimension-free robustness estimate for this inequality: by introducing a new metric to measure the distance between the set A and its corresponding half-space H (namely the distance between the two centroids), we show that the deficit S_rho(H) - S_rho(A) can be controlled from both below and above by essentially the same function of the distance, up to logarithmic factors. As a consequence, we also establish the conjectured exponent in the robustness estimate proven by Mossel-Neeman, which uses the total-variation distance as a metric. In the limit rho->1, we get an improved dimension free robustness bound for the Gaussian isoperimetric inequality. Our estimates are also valid for a the more general version of stability where more than two correlated vectors are considered.

Postural instability detection: aging and the complexity of spatial-temporal distributional patterns for virtually contacting the stability boundary in human stance.

Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP) or center-of-mass (COM) fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC) is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary ( = limits of the region of feasible COP or COM displacement) and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC), a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a predictive model of postural instability during upright stance.

Estabilidade da marcha na neuropatia diabética periférica

The aim of this study was to evaluate gait stability in diabetic patients with peripheral neuropathy in three conditions: habitual walking with eyes open, walking with eyes closed, and walking with eyes open and narrow base of support. The study included 41 subjects, 18 with neuropathy (NG) and 23 controls. Gait stability was evaluated on a baropodometer using the Footwalk Pro software. The following data were obtained: gait speed and percentage of time spent in double stance and single stance. Significant differences were observed between groups in all three conditions for gait speed and single stance time, which were reduced in NG (p<0.05), and for double stance time, which was increased in NG (p<0.05). For gait speed, double stance time and single stance time, the eyes open condition differed from the eyes closed (p<0.001) and narrow base of support (p<0.001) conditions. In the three conditions studied, patients of NG presented a deficit in gait stability and this performance was even more compromised in the two conditions that required greater postural control. These gait changes resulting from the complexity imposed by the different conditions suggest the inclusion of these conditions in the evaluation and treatment of this population.

Relative stability of neurocognitive deficits in early onset schizophrenia spectrum patients

In contrast to the findings of progressive structural brain changes in adolescence, longitudinal studies of patients with early onset schizophrenia spectrum disorders (EOS) indicate that neurocognitive deficits are relatively stable over the first years. The aim of this study is to assess neurocognitive functions longitudinally in patients with EOS compared to healthy controls (HC) using the MATRICS Cognitive Consensus Battery (MCCB). MethodsTwenty patients with EOS and 41 HC were tested with the MCCB at baseline (T1) and after one (T2) and two years (T3). The mean age for the EOS group was 15.6 (SD=1.8) years, while the mean duration of illness was 1.7 (SD=1.4) years at T1. ResultsThe EOS group's neurocognitive performances indicate a stable deficit on most measures. Both the EOS and HC groups showed improved neurocognitive functioning over time on all measures except for the verbal learning domain. There was an interaction between the EOS and HC groups' performance over time on the Trail Making Test A (TMA), a subtest on the processing speed domain. ConclusionThe longitudinal neurocognitive performances measured by the MCCB confirm previous findings of stable deficits in patients with EOS. It is premature to conclude whether the increases in neurocognitive performance reflect developmental processes in adolescence or may be explained by learning effects, or both. As opposed to the other tests in this domain, a stagnation in processing speed as measured by the TMA suggests that the TMA is a particularly sensitive measure of neurodevelopmental deviance in EOS.

THE EFFECT OF LOCALISED AND GLOBALISED FATIGUE ON CENTRE OF PRESSURE EXCURSIONS IN HEALTHY AND FUNCTIONALLY UNSTABLE PARTICIPANTS FOLLOWING A SINGLE LEG DROP JUMP LANDING; ANALYSING A SUBCONSCIOUS TIME PERIOD

BackgroundIt has been reported that fatigue and stability deficits may be predispositions to musculoskeletal injury in functional ankle instability (FAI) sufferers. Analysis of subconscious time periods (initial 200 ms) may...

POSTURAL STABILITY DURING THE TRANSITION FROM DOUBLE-LEG STANCE TO SINGLE-LEG STANCE IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTED SUBJECTS

BackgroundDespite recent advances in rehabilitation and secondary prevention strategies after anterior cruciate ligament reconstruction (ACLR), re-injury rates remain high and long-term outcomes are often disappointing. Deficits in postural stability are...

Gross Motor Function of A Child With Neurodegeneration With Brain Iron Accumulation (NBIA)

Introduction. Neurodegeneration with brain iron accumulation (NBIA) involves a group of progressive extrapyramidal disorders characterised by iron accumulation in the brain. Objective. to de­scribe the gross motor function of a child with clinical diagnosis of NBIA. Method. This is a case report involving a 7-year-old child and clinical diagnosis of NBIA. This study evaluated the history of the disease and the neuromotor functions of the child using a neurological physiotherapy evaluation form. The GMFM - Gross Motor Function Measure, a system of quantitative assessment of gross motor function in five broad dimensions, was applied. Case Presentation. Magnetic resonance imaging (MRI) showed the eye-of-the-tiger sign in the me­dial globus pallidus. Clinical examination presented extrapyramidal signs like dystonia, choreoathetosis, dysarthria and visual impairment. In this case, the combination of clinical and MRI findings was con­sistent with NBIA. Results. In the A dimension (down and roll) of GMFM, the child achieve a score of 39 points (76% of the gross mo­tor function); in the B dimension (sit) she achieve a total score of 60 points (30% of the function); in the C dimension (crawl and kneel) she achieve a score of 1 point (2% of the function); in the D dimen­sion (standing position) and in the E dimension (walk, run and jump) she did not score in any item. Conclusion. The significant deficit in proximal stability and frequent extensor dystonic spasms affected the child’s functional performance.