Postural System Research Articles

Time scale dependence of the center of pressure entropy: What characteristics of the neuromuscular postural control system influence stabilographic entropic half-life?

The center of pressure (COP) movement in studies of postural control reveals a highly regular structure (low entropy) over short time periods and a highly irregular structure over large time scales (high entropy). Entropic half-life (EnHL) is a novel measure that quantifies the time over which short-term temporal correlations in a time series deteriorate to an uncorrelated, random structure. The current study suggested and tested three hypotheses about how characteristics of the neuromuscular postural control system may affect stabilometric EnHL: (H1) control system activity hypothesis: EnHL decreases with increased frequency of control system interventions adjusting COP motion; (H2) abundance of states hypothesis: EnHL decreases with increased number of mechanically equivalent states available to the postural system; and (H3) neurologic process hierarchy hypothesis: EnHL increases if postural control functions shift from the spinal level to the motor cortex. Thirty healthy participants performed quiet stance tests for 90 s in 18 different conditions: stance (bipedal, one-legged, and tandem); footwear (bare foot, regular sports shoe, and rocker sole shoes); and simultaneous cognitive task (two-back working memory task, no challenge). A four-way repeated-measures ANOVA revealed significant changes in EnHL for the different stance positions and for different movement directions (medio-lateral, anterior-posterior). These changes support H1 and H2. Significant differences were also found between rocker sole shoes and normal or barefoot standing, which supports H3. This study contributes to the understanding of how and why EnHL is a useful measure to monitor neuromuscular control of balance.

Oculomotor tasks affect differently postural control in healthy children

Eye movements affect postural stability in children. The present study focuses on the effect of different types of eye movements on postural stability in healthy children.Both eye movements and postural stability have been recorded in 51 healthy children from 6.3 to 15.5 years old. Eye movements were recorded binocularly with a video oculography (MobilEBT®), and postural stability was measured while child was standing on a force platform (TechnoConcept®). Children performed three oculomotor tasks: saccades, pursuits and reading a text silently. We measured the number of saccades made in the three oculomotor tasks, the number of words read, and the surface area, the length and mean velocity of the center of pressure (CoP).According to previous studies, postural control improves with age until 10–12 years. Saccades toward a target as well as during a reading task reduce significantly the CoP displacement and its velocity, while during pursuit eye movements all children increase postural parameters (i.e., the surface area, the length and mean velocity of the CoP).These results suggest the presence of an interaction between the oculomotor control and the postural system. Visual attention to perform saccades (to stationary targets or to words) influences postural stability more than the frequency of saccade triggering does.

Influence of temporal pressure constraint on the biomechanical organization of gait initiation made with or without an obstacle to clear.

Many daily motor tasks have to be performed under a temporal pressure constraint. This study aimed to explore the influence of such constraint on motor performance and postural stability during gait initiation. Young healthy participants initiated gait at maximal velocity under two conditions of temporal pressure: in the low-pressure condition, gait was self-initiated (self-initiated condition, SI); in the high-pressure condition, it was initiated as soon as possible after an acoustic signal (reaction-time condition, RT). Gait was initiated with and without an environmental constraint in the form of an obstacle to be cleared placed in front of participants. Results showed that the duration of postural adjustments preceding swing heel-off ("anticipatory postural adjustments", APAs) was shorter, while their amplitude was larger in RT compared to SI. These larger APAs allowed the participants to reach equivalent postural stability and motor performance in both RT and SI. In addition, the duration of the execution phase of gait initiation increased greatly in the condition with an obstacle to be cleared (OBST) compared to the condition without an obstacle (NO OBST), thereby increasing lateral instability and thus involving larger mediolateral APA. Similar effects of temporal pressure were obtained in NO OBST and OBST. This study shows the adaptability of the postural system to temporal pressure in healthy young adults initiating gait. The outcome of this study may provide a basis for better understanding the aetiology of balance impairments with the risk of falling in frail populations while performing daily complex tasks involving a whole-body progression.

Body Sway as a Possible Indicator of Fatigue in Clerical Workers.

BackgroundFatigue has a strong impact on workers' performance and safety, but expedient methods for assessing fatigue on the job are not yet available. Studies discuss posturography as an indicator of fatigue, but further evidence for its use in the workplace is needed. The purpose of the study is to examine whether posturography is a suitable indicator of fatigue in clerical workers.MethodsThirty-six employees (Ø 34.8 years, standard deviation = 12.5) participated in postural tasks (eyes open, eyes closed, arm swinging, and dual task) in the morning and afternoon. Position of their center of pressure (COP) was registered using a Nintendo Wii Balance Board and commercial software. From registered COP time series, we calculated the following parameters: path length (mm), velocity (mm/s), anterior–posterior variance (mm), mediolateral variance (mm), and confidence area (mm2). These parameters were reduced to two orthogonal factors in a factor analysis with varimax rotation.ResultsStatistical analysis of the first factor (path length and velocity) showed a significant effect of time of day: COP moved along a shorter path at a lower velocity in the afternoon compared with that in the morning. There also was a significant effect of task, but no significant interaction.ConclusionData suggest that postural stability of clerical workers was comparable in the morning and afternoon, but COP movement was greater in the morning. Within the framework of dynamic systems theory, this could indicate that the postural system explored the state space in more detail, and thus was more ready to respond to unexpected perturbations in the morning.

Application of a novel spinal posture and motion measurement system in active and static sitting

The quantification of work-related musculoskeletal risk factors is of great importance; however, only a few tools allow objective, unrestricted measurements of spinal posture and motion in workplaces. This study was performed to evaluate the applicability of the Epionics system in a sedentary workplace. The system is mobile and wireless and assesses lumbar lordosis, pelvic orientation and spinal motion, without restricting subjects in their movements. In total, 10 males were monitored while sitting for 2 h on static and dynamic office chairs and on an exercise ball, to evaluate the effect of dynamic sitting. The volunteers were able to perform their work unhampered. No differences among the tested furniture could be detected with respect to either the lordosis or the number of spinal movements after habituation to the furniture; however, differences in pelvic orientation were statistically significant. The results of the present study indicate that Epionics may be useful for the quantitative assessment of work-related risk factors.

TEENAGE MALE WITH MILD TRAUMATIC BRAIN INJURY IMPROVED THROUGH A COMPREHENSIVE NEUROREHABILITATION REGIMEN

Event Abstract Back to Event TEENAGE MALE WITH MILD TRAUMATIC BRAIN INJURY IMPROVED THROUGH A COMPREHENSIVE NEUROREHABILITATION REGIMEN Frederick R. Carrick1*, David J. Traster1* and Susan Esposito2* 1 Carrick Institute, United States 2 Life University, United States Background: We describe a 17 year-old male who presents with a five year history of concussions. Symptoms include headaches, light and sound sensitivity, fogginess, lightheadedness, trouble concentrating and reading, memory difficulties, fatigue, nausea and decreased appetite associated with weight loss. Methods: Comprehensive neurologic examination demonstrates a downbeat nystagmus when visual fixation was eliminated. Comprehensive Assessment of Postural Systems (CAPS) testing during perturbed surface, eyes closed, head in neutral parameters, revealed a 59.3% stability score. The patient participated in a neurorehabilitation program that included off-vertical-axis-rotation vestibular rehabilitation, specific neurorehabilitation exercises, times-one viewing gaze stabilization exercises, somato-sensory evoked potential activation of the left trigeminal system, breathing exercises and passive, multi-planar movements of right proximal extremities. Results: The combination of treatment protocols produced profound changes to all signs and symptoms associated with the mild traumatic brain injury. Follow up CAPS results during perturbed surface, eyes closed, head in neutral parameters, revealed a 74.9% stability score and a return to exercise was achieved. Conclusion: This case showed significant improvements after administration of a multimodal neurorehabilitation regimen. The authors suggest further investigation into vestibular rehabilitation mechanisms and brain-based approaches to patient treatments with mild traumatic brain injuries. Keywords: Traumatic brain injury (TBI), concussion, concussion rehabilitation, Neurorehabilitation, Balance control Conference: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration, Orlando, Florida, United States, 10 Dec - 14 Dec, 2015. Presentation Type: Poster Presentation Topic: Case Reports for Poster Presentation Citation: Carrick FR, Traster DJ and Esposito S (2015). TEENAGE MALE WITH MILD TRAUMATIC BRAIN INJURY IMPROVED THROUGH A COMPREHENSIVE NEUROREHABILITATION REGIMEN. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration. doi: 10.3389/conf.fneur.2015.58.00104 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Sep 2015; Published Online: 02 Nov 2015. * Correspondence: Prof. Frederick R Carrick, Carrick Institute, Cape Canaveral, United States, drfrcarrick@post.harvard.edu Dr. David J Traster, Carrick Institute, Cape Canaveral, United States, dtraster3@gmail.com Dr. Susan Esposito, Life University, Marietta, United States, susan.esposito@life.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Frederick R Carrick David J Traster Susan Esposito Google Frederick R Carrick David J Traster Susan Esposito Google Scholar Frederick R Carrick David J Traster Susan Esposito PubMed Frederick R Carrick David J Traster Susan Esposito Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Correlation between balance and gait according to pelvic displacement in stroke patients.

[Purpose] The purpose of this study was to investigate the correlations of balance and gait according to pelvic displacement in stroke patients. [Subjects] The subjects of this study were 58 stroke patients who had been admitted to a hospital. [Methods] A Global Postural System was used to measure pelvic displacement. To measure the balance ability, a Tetrax balance system was used to measure the weight distribution index and stability index. Gait ability was measured during the 10-Meter Walking Test and Figure-of-8 Walk Test. [Results] The results of this study showed that was significant positive correlation between the anterior superior iliac spine height difference in pelvic displacement and the weight distribution index and significant positive correlation between the posterior superior iliac spine height difference and the stability index in the normal position with the eyes closed. Statistically significant positive correlation also was found between the anterior superior iliac spine height difference and the straight and curved gait ability. [Conclusion] The increased pelvic displacement in stroke patients results in a decrease in balance ability and gait speed. This suggests that control of pelvic displacement is necessary before functional training for patients with stroke.

The effect of a pelvis-concentrated exercise program on male college students’ body alignment and foot base pressure

[Purpose] The aim of this study was to examine the effect of a pelvis-concentrated exercise program and walking on the changes in body shape and foot base pressure. [Subjects and Methods] Thirty adults from K University in Busan, Republic of Korea, were randomly divided into the Swiss-ball exercise group and McKenzie exercise group, and they conducted exercise for 40 min 3 times a week for 6 weeks. [Results] Global postural system results and foot base pressure significantly decreased in both groups. A comparison of foot base pressure after the intervention between the two groups revealed that the Swiss-ball exercise group exhibited a greater reduction than the McKenzie exercise group. [Conclusion] The results of this study indicated that the Swiss-ball exercise may improve posture and foot base pressure in male adults.

MULTIMODAL NEUROREHABILITATION IMPROVE MILD TRAUMATIC BRAIN INJURY

Event Abstract Back to Event MULTIMODAL NEUROREHABILITATION IMPROVE MILD TRAUMATIC BRAIN INJURY Frederick R. Carrick1*, David J. Traster1*, Susan Esposito2* and Derek A. Barton1* 1 Carrick Institute, United States 2 Life University, United States Background: We describe a male in his 20’s who presents with a history of multiple concussions resulting in bilateral headaches, visual disturbances, dizziness and fatigue. Methods: Comprehensive neurologic examination revealed saccadic intrusions within all direction of pursuits. Horizontal saccades were slow with glissades. Optokinetic responses had a decreased gain in all directions. A left beating nystagmus was revealed when fixation was eliminated. Comprehensive Assessment of Postural Systems (CAPS) testing during perturbed surface, eyes closed, head in extension parameters, revealed a 15.5% stability score. The patient participated in a five day neurorehabilitation program that included off-vertical-axis-rotation vestibular rehabilitation, times-one viewing gaze stabilization exercises, somatosensory evoked potential stimulation of the left trigeminal system, oculomotor rehabilitation strategies and spinal manipulations. Results: The combination of treatment protocols allowed the patient to return to his work place symptom free. Follow up CAPS results during perturbed surface, eyes closed, head in extension parameters, revealed a 53.6 stability score. Conclusion: This case showed significant improvements as a result of the multimodal neurorehabilitation regimen described. The authors suggest further investigation into vestibular rehabilitation and brain-based therapies to patient treatments with mild traumatic brain injuries. Keywords: concussion, concussion rehabilitation, Neurorehabilitation, Traumatic brain injury (TBI), Postoperative Complications Conference: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration, Orlando, Florida, United States, 10 Dec - 14 Dec, 2015. Presentation Type: Poster Presentation Topic: Case Reports for Poster Presentation Citation: Carrick FR, Traster DJ, Esposito S and Barton DA (2015). MULTIMODAL NEUROREHABILITATION IMPROVE MILD TRAUMATIC BRAIN INJURY. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration. doi: 10.3389/conf.fneur.2015.58.00110 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Sep 2015; Published Online: 02 Nov 2015. * Correspondence: Prof. Frederick R Carrick, Carrick Institute, Cape Canaveral, United States, drfrcarrick@post.harvard.edu Dr. David J Traster, Carrick Institute, Cape Canaveral, United States, dtraster3@gmail.com Dr. Susan Esposito, Life University, Marietta, United States, susan.esposito@life.edu Dr. Derek A Barton, Carrick Institute, Cape Canaveral, United States, derekabarton@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Frederick R Carrick David J Traster Susan Esposito Derek A Barton Google Frederick R Carrick David J Traster Susan Esposito Derek A Barton Google Scholar Frederick R Carrick David J Traster Susan Esposito Derek A Barton PubMed Frederick R Carrick David J Traster Susan Esposito Derek A Barton Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Putative spinal interneurons mediating postural limb reflexes provide a basis for postural control in different planes.

The dorsal-side-up trunk orientation in standing quadrupeds is maintained by the postural system driven mainly by somatosensory inputs from the limbs. Postural limb reflexes (PLRs) represent a substantial component of this system. Earlier we described spinal neurons presumably contributing to the generation of PLRs. The first aim of the present study was to reveal trends in the distribution of neurons with different parameters of PLR-related activity across the gray matter of the spinal cord. The second aim was to estimate the contribution of PLR-related neurons with different patterns of convergence of sensory inputs from the limbs to stabilization of body orientation in different planes. For this purpose, the head and vertebral column of the decerebrate rabbit were fixed and the hindlimbs were positioned on a platform. Activity of individual neurons from L5 to L6 was recorded during PLRs evoked by lateral tilts of the platform. In addition, the neurons were tested by tilts of the platform under only the ipsilateral or only the contralateral limb, as well as during in-phase tilts of the platforms under both limbs. We found that, across the spinal gray matter, strength of PLR-related neuronal activity and sensory input from the ipsilateral limb decreased in the dorsoventral direction, while strength of the input from the contralateral limb increased. A near linear summation of tilt-related sensory inputs from different limbs was found. Functional roles were proposed for individual neurons. The obtained data present the first characterization of posture-related spinal neurons, forming a basis for studies of postural networks impaired by injury.

A Novel Approach to Detect the Posture of Excavator’s Manipulator

In the study of excavator automation, the conventional contact-type sensors can be easily damaged because of the collision or vibration when measuring the posture of excavator’s manipulator. For this case, a novel vision-based approach for measuring the posture of excavator’s manipulator is proposed. In this approach, an industrial camera with an infrared filter is used to grab the perspective images of the manipulator under the irradiation of a LED infrared light source; and saddle point detection is adopted to detect the man-made targets which fixed on every arm of the manipulator. Then the selection algorithm based on the fixed geometric dimensioning between two targets is optimized to select the saddle point in targets, and the posture angle of the corresponding arm can be derived from the saddle point coordinates. Furthermore, the detection regions are tracked by anticipating the three group targets’ movement separately. Experiments show that with the infrared device, the vision-based posture measurement system of the excavator’s manipulator can better adapt to different illumination intensity conditions; and the optimization of target selection algorithm reduces the false detection rate from 4 times in every 30s to 1 time in every 30s; also, the average processing time for every manipulator movement frame is reduced from about 70 ms to 50ms by tracking the detection regions separately.

Contribution of supraspinal systems to generation of automatic postural responses.

Different species maintain a particular body orientation in space due to activity of the closed-loop postural control system. In this review we discuss the role of neurons of descending pathways in operation of this system as revealed in animal models of differing complexity: lower vertebrate (lamprey) and higher vertebrates (rabbit and cat). In the lamprey and quadruped mammals, the role of spinal and supraspinal mechanisms in the control of posture is different. In the lamprey, the system contains one closed-loop mechanism consisting of supraspino-spinal networks. Reticulospinal (RS) neurons play a key role in generation of postural corrections. Due to vestibular input, any deviation from the stabilized body orientation leads to activation of a specific population of RS neurons. Each of the neurons activates a specific motor synergy. Collectively, these neurons evoke the motor output necessary for the postural correction. In contrast to lampreys, postural corrections in quadrupeds are primarily based not on the vestibular input but on the somatosensory input from limb mechanoreceptors. The system contains two closed-loop mechanisms – spinal and spino-supraspinal networks, which supplement each other. Spinal networks receive somatosensory input from the limb signaling postural perturbations, and generate spinal postural limb reflexes. These reflexes are relatively weak, but in intact animals they are enhanced due to both tonic supraspinal drive and phasic supraspinal commands. Recent studies of these supraspinal influences are considered in this review. A hypothesis suggesting common principles of operation of the postural systems stabilizing body orientation in a particular plane in the lamprey and quadrupeds, that is interaction of antagonistic postural reflexes, is discussed.

The influence of different modes of ventilation on standing balance of athletes.

Background:The respiratory movements are one of the factors influencing standing balance. Although well-trained athletes have better postural performance compared to untrained men, it's not quite clear, if the formers' upright posture would be more stable during different ventilation modes, maximal voluntary hyperventilation and inspiratory breath-holding. There are no studies on this subject in the available literature.Objectives:The aim of this study was to investigate an influence of maximal inspiratory breath-holding and maximal voluntary hyperventilation on the standing balance of athletes.Patients and Methods:We assessed the amplitude and the velocity of postural sway in the athletes (n = 38) and untrained subjects (n = 28) by the force platform. The frequency characteristics of the center of pressure (CP) oscillations' were also analyzed. The amplitude and the frequency of respiratory movements were estimated by the strain gauge.Results:It was found that during quiet breath velocity and frequency of CP oscillations were lower in the athletes. Breath holding led to an increase of velocity and frequency of CP displacement in both groups, increase of these indices was more pronounced in the athletes. Maximal voluntary hyperventilation caused a significant increase of all stabilographic indices in both groups. Increase of frequency and amplitude of respiratory movements were mainly observed during hyperventilation in athletes and it caused an increase of the velocity of CP displacement. Changes of sway amplitude were the same in both groups.Conclusions:Breath holding led to activation of the postural control, which was more pronounced in the athletes. Hyperventilation caused an impairment of the postural stability. The athletes' postural system compensated the impact of hyperventilation more efficiently versus controls, but it was achieved at the expense of greater effort.

Effects of intervertebral disc disorders of low back on the mandibular kinematic: kinesiographic study.

BackgroundIntervertebral disc disorders are one of the most common causes of low back pain. Neuromuscular dysfunction frequently is present in patients with lumbar disc herniation.When considering joint dysfunction, it is important to remember that the spine functions as a unit. Dysfunction on one level can trigger compensatory changes in other spinal levels or in other areas of the musculoskeleton. Findings demonstrated the relationship between stomatognathic and postural systems justifying the hypothesis that muscular-skeletal impairment in one system could affect the other one. However, evidence that a lumbar intervertebral disc herniation could influence the mandibular kinematics is still lacking. Aim of this study was to analyse the effects that intervertebral disc herniation of low back could have on the mandibular kinematics.FindingsKinesiographic evaluations of the mandibular dynamics of 23 adult patients suffering L4/L5 and L5/S1 lumbosacral disc hernation were compared with a non pathological control group. A statistically significant difference of maximal mouth opening (p < .05) and of maximal mouth opening velocity (p < .03) was found comparing the study patients with the control subjects.ConclusionLumbosacral disc herniation appears to be associated with changes in the activity of mandibular kinematics both in rate and quality of movement. The study suggests the existence of connections between masticatory system and lumbar disk herniation.

Global Body Posture and Plantar Pressure Distribution in Individuals With and Without Temporomandibular Disorder: A Preliminary Study

ObjectiveThe aim of this study was to evaluate body posture and the distribution of plantar pressure at physiologic rest of the mandible and during maximal intercuspal positions in subjects with and without temporomandibular disorder (TMD). MethodsFifty-one subjects were assessed by the Diagnostic Criteria for Research on Temporomandibular Disorders and divided into a symptomatic group (21) and an asymptomatic group (30). Postural analysis for both groups was conducted using photogrammetry (SAPo version 0.68; University of São Paulo, São Paulo, Brazil). The distribution of plantar pressures was evaluated by means of baropodometry (Footwork software), at physiologic rest and maximal intercuspal positions. ResultsOf 18 angular measurements, 3 (17%) were statistically different between the groups in photogrammetric evaluation. The symptomatic group showed more pronounced cervical distance (P = .0002), valgus of the right calcaneus (P = .0122), and lower pelvic tilt (P = .0124). The baropodometry results showed the TMD subjects presented significantly higher rearfoot and lower forefoot distribution than those in the asymptomatic group. No differences were verified in maximal intercuspal position in the between-group analysis and between the 2 mandibular positions in the within-group analysis. ConclusionsSubjects with and without TMD presented with global body posture misalignment. Postural changes were more pronounced in the subjects with TMD. In addition, symptomatic subjects presented with abnormal plantar pressure distribution, suggesting that TMD may have an influence on the postural system.

Redundant Method for Measuring Downhole Posture of the Steering Drilling Tool

Exact downhole posture measurement of steering drilling tool can provide reliable control parameters for downhole control system, so as to ensure the accurate control of hole trajectory. How to ensure the reliability of the posture measurement system while it works in harsh environment is a key technique in the engineering process of steering drilling system. A redundant measurement method based on multi-accelerometers has been put forward according to the analysis of the working environment and measurement reliability requirements of posture measurement system. Then the posture parameter solution formulas were given. According to the linear relationship between measurement signals, a reconfiguration method of the redundant measurement system was put forward to ensure the fault-tolerant operation of the system.

Visual Reliance for Balance Control in Older Adults Persists When Visual Information Is Disrupted by Artificial Feedback Delays

Sensory information from our eyes, skin and muscles helps guide and correct balance. Less appreciated, however, is that delays in the transmission of sensory information between our eyes, limbs and central nervous system can exceed several 10s of milliseconds. Investigating how these time-delayed sensory signals influence balance control is central to understanding the postural system. Here, we investigate how delayed visual feedback and cognitive performance influence postural control in healthy young and older adults. The task required that participants position their center of pressure (COP) in a fixed target as accurately as possible without visual feedback about their COP location (eyes-open balance), or with artificial time delays imposed on visual COP feedback. On selected trials, the participants also performed a silent arithmetic task (cognitive dual task). We separated COP time series into distinct frequency components using low and high-pass filtering routines. Visual feedback delays affected low frequency postural corrections in young and older adults, with larger increases in postural sway noted for the group of older adults. In comparison, cognitive performance reduced the variability of rapid center of pressure displacements in young adults, but did not alter postural sway in the group of older adults. Our results demonstrate that older adults prioritize vision to control posture. This visual reliance persists even when feedback about the task is delayed by several hundreds of milliseconds.

The filtering of the posturographic signals shows the age related features.

Objective. Lower frequencies of slow oscillations of the posturographic signals can be removed using high-pass filtering. This procedure releases postural reflexes possessing higher frequencies and lower amplitude range. Mutual dependence between the x and y components of posturographic signals was analyzed using principal component analysis (PCA). The posturographic signals of old patients with idiopathic gait disturbance were compared with the control group of similar age and with younger patients. There was also the analysis of the influence of the eyes state (open versus closed) and the head position (normal or bent back). The statistically significant differences in the mutual dependence between x and y components between the groups of patients were analyzed using MANOVA. The significant differences were observed mainly in the range of filter frequencies f = 0.1–1.5 Hz and f = 2.2–5.5 Hz with a maximum effect at approximately 4-5 Hz. A detailed post-hoc analysis is also presented. The differences in the higher frequency range suggest the main disturbance to be connected with the spinal reflexes. Visual and vestibular support appear insufficient for postural stability control in the idiopathic gait disturbance group. The results suggest that idiopathic gait disturbance is the final stage of the aging process of postural system.

Effects of Reversible Spinalization on Individual Spinal Neurons

Postural limb reflexes (PLRs) represent a substantial component of the postural system responsible for stabilization of dorsal-side-up trunk orientation in quadrupeds. Spinalization causes spinal shock, that is a dramatic reduction of extensor tone and spinal reflexes, including PLRs. The goal of our study was to determine changes in activity of spinal interneurons, in particular those mediating PLRs, that is caused by spinalization. For this purpose, in decerebrate rabbits, activity of individual interneurons from L5 was recorded during stimulation causing PLRs under two conditions: (1) when neurons received supraspinal influences and (2) when these influences were temporarily abolished by a cold block of spike propagation in spinal pathways at T12 ("reversible spinalization"; RS). The effect of RS, that is a dramatic reduction of PLRs, was similar to the effect of surgical spinalization. In the examined population of interneurons (n = 199), activity of 84% of them correlated with PLRs, suggesting that they contribute to PLR generation. RS affected differently individual neurons: the mean frequency decreased in 67% of neurons, increased in 15%, and did not change in 18%. Neurons with different RS effects were differently distributed across the spinal cord: 80% of inactivated neurons were located in the intermediate area and ventral horn, whereas 50% of nonaffected neurons were located in the dorsal horn. We found a group of neurons that were coactivated with extensors during PLRs before RS and exhibited a dramatic (>80%) decrease in their activity during RS. We suggest that these neurons are responsible for reduction of extensor tone and postural reflexes during spinal shock.

Children’s Catching Performance When the Demands on the Postural System Is Altered

In many dynamic interceptive actions performers need to integrate activity of manual and postural subsystems for successful performance. Groups of different skill level (poor and good catchers), (mean age = 9.1 and 9.4 respectively) were required to perform one-handed catches under different postural constraints: standing; standing in contact with a postural support aid by their side (PSAS) or to the left of their trunk (PSAF); Tandem; and sitting (control). Results revealed that, for poor catchers, the number of successful catches increased and grasp errors decreased significantly when sitting and with both postural aids in comparison with standing alone and Tandem conditions. Kinematic analyses showed that the postural aid devices reduced head sway in the anterior-posterior direction, while the PSAF reduced lateral head sway. The poor catchers' performance benefited from an enlarged support surface, and reduction of lateral sway. Good catchers performed successfully under all task constraints, signifying the existence of a functional relationship between postural and grasping subsystems during performance. The results are discussed in the frame of Bernstein's (1967) and Newell's (1986) theory.