Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.     

Postural stability in diabetic polyneuropathy

OBJECTIVE: To examine whether sensory changes in lower limbs associated with diabetic sensory polyneuropathy compromise postural stability in different visual sensory conditions. RESEARCH DESIGN AND METHODS: The presence and severity of sensory neuropathy was evaluated with a clinical scale and measures of nerve conduction velocity in the lower limbs. Balance control was evaluated by testing subjects' postural stability (with a force platform) with vision, without vision, and during a recovery period after being without vision. RESULTS: Neuropathic patients showed larger ranges of sway, a faster sway speed, and a greater dispersion of sway than control subjects in all conditions. They also exhibited similar or less stable postural performance with vision than that of control subjects without vision. There was a strong relationship between the severity of the neuropathy and the postural stability. CONCLUSIONS: This experiment highlights that even with vision, the postural stability of neuropathic patients is impaired and may put them at higher risk of falling when performing more challenging daily tasks.     

Age-associated differences in sensori-motor function and balance in community dwelling women

Tests of visual, vestibular, sensori-motor and balance function were administered to 550 women, aged between 20 and 99 years at a Balance and Gait Laboratory. All of the sensory, motor and balance system measures showed significant age-associated differences. Multiple regression analyses revealed that the measures of lower limb sensation were the consistent sensori-motor factors contributing to balance under normal conditions (standing on a firm surface with eyes open or closed). Under more challenging conditions (standing on foam with eyes open) vision, strength and reaction time played significant roles, whilst when standing on foam with eyes closed, vestibular function also made a significant contribution. Analysis of percentage increases in sway under conditions where visual and peripheral sensation systems were removed or diminished, compared with sway under optimal conditions, indicated that up until age 65 there was an increased reliance on vision for balance control. Beyond this age, the contribution made by vision declined, so that in the oldest age-groups reduced vision was less able to supplement peripheral input, resulting in increased sway areas. Peripheral sensation however was the most important sensory system in the maintenance of static postural stability at all ages.     

Sensory strategies in human postural control before and after unilateral vestibular neurotomy

Vestibular inputs tonically activate the anti-gravitative leg muscles during normal standing in humans, and visual information and proprioceptive inputs from the legs are very sensitive sensory loops for body sway control. This study investigated the postural control in a homogeneous population of 50 unilateral vestibular-deficient patients (Ménière's disease patients). It analyzed the postural deficits of the patients before and after surgical treatment (unilateral vestibular neurotomy) of their diseases and it focused on the visual contribution to the fine regulation of body sway. Static posturographic recordings on a stable force-plate were done with patients with eyes open (EO) and eyes closed (EC). Body sway and visual stabilization of posture were evaluated by computing sway area with and without vision and by calculating the percentage difference of sway between EC and EO conditions. Ménière's patients were examined when asymptomatic, 1 day before unilateral vestibular neurotomy, and during the time-course of recovery (1 week, 2 weeks, 1 month, 3 months, and 1 year). Data from the patients were compared with those recorded in 26 healthy, age- and sex-matched participants. Patients before neurotomy exhibited significantly greater sway area than controls with both EO (+52%) and EC (+93%). Healthy participants and Ménière's patients, however, displayed two different behaviors with EC. In both populations, 54% of the subjects significantly increased their body sway upon eye closure, whereas 46% exhibited no change or significantly swayed less without vision. This was statistically confirmed by the cluster analysis, which clearly split the controls and the patients into two well-identified subgroups, relying heavily on vision (visual strategy, V) or not (non-visual strategy, NV). The percentage difference of sway averaged +36.7%+/-10.9% and -6.2%+/-16.5% for the V and NV controls, respectively; +45.9%+/-16.8% and -4.2%+/-14.9% for the V and NV patients, respectively. These two distinct V and NV strategies seemed consistent over time in individual subjects. Body sway area was strongly increased in all patients with EO early after neurotomy (1 and 2 weeks) and regained preoperative values later on. In contrast, sway area as well as the percentage difference of sway were differently modified in the two subgroups of patients with EC during the early stage of recovery. The NV patients swayed more, whereas the V patients swayed less without vision. This surprising finding, indicating that patients switched strategies with respect to their preoperative behavior, was consistently observed in 45 out of the 50 Ménière's patients during the whole postoperative period, up to 1 year. We concluded that there is a differential weighting of visual inputs for the fine regulation of posture in both healthy participants and Ménière's patients before surgical treatment. This differential weighting was correlated neither with age or sex factors, nor with the clinical variables at our disposal in the patients. It can be accounted for by a different selection of sensory orientation references depending on the personal experience of the subjects, leading to a more or less heavy dependence on vision. The change of sensory strategy in the patients who had undergone neurotomy might reflect a reweighting of the visual and somatosensory cues controlling balance. Switching strategy by means of a new sensory selection of orientation references may be a fast adaptive response to the lesion-induced postural instability.     

Children's postural sway in response to low- and high-frequency visual information for oscillation.

Two experiments examined postural responses of 3- to 6-year-old children to visual information for oscillation. In Experiment 1, children saw oscillations of the surround, with these movements ranging in frequency between 0.2 and 0.8 Hz. Analyses of anterior-posterior postural sway revealed that, similar to previous developmental investigations, the frequency of sway matched the frequency of oscillations. Analyses of sway amplitude and timing, however, revealed patterns of results more in keeping with research on adults. Experiment 2 extended these findings, presenting oscillations in which the frequency changed during the trial. Analyses of anterior-posterior sway revealed that sway frequency matched both speeds of movement. In contrast, amplitude and timing measures were again in line with adult data. These results suggest that the postural sway of children contains both adultlike and nonadultlike parameters of balance control. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Roles of retinal periphery and depth periphery in linear vection and visual control of standing in humans.

Two groups of 60 adults (mean ages 23.7 and 29.3 yrs) were exposed to central and/or peripheral visual motion affecting either the foreground or the background of the visual field. Body sway and duration of vection over a 1-min period were measured. Results show that depth periphery and retinal periphery both play a role in the regulation of posture and in vection. Movement limited to the foreground produced little vection or postural sway compared with motion located in the background. Results also show that motion covering the periphery of the visual field is more efficient in inducing vection and body sway than motion restricted to the center of the visual field. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of sensory manipulation on postural control in Parkinson's disease

Postural control was assessed on a tilting platform system in 20 patients with idiopathic Parkinson's disease and 20 age-matched controls. The amount of information provided by vision and lower limb proprioception was varied during the experiment to investigate the influence of changes in sensory cues on postural control. The patient group with clinical evidence of impaired postural control (Hoehn and Yahr III) had significantly higher sway scores over all sensory conditions than either the Hoehn and Yahr II group or controls. The pattern of sway scores indicated that no obvious deficit in the quality, or processing, of sensory information was responsible for the postural instability observed in this group. The patients in both Hoehn and Yahr groups were also able to respond appropriately to potentially destabilising sensory conflict situations and significantly improved their sway scores when provided with visual feedback of body sway. The results indicate that in Parkinson's disease, the main site of dysfunction in postural control is likely to be at a central motor level.     

Developmental Differences in the Function and Use of Anatomical Dolls During Interviews With Alleged Sexual Abuse Victims.

The impact of anatomical dolls on reports provided by 3- to 12-year-old alleged sexual abuse victims (N = 178) was examined. Children produced as many details in response to open-ended invitations with and without the dolls. In response to directive questions, the 3- to 6-year-olds were more likely to reenact behaviorally than to report verbally, whereas the 7- to 12-year-olds produced more verbal details than enactments when using the dolls. With the dolls, the younger children were more likely than the older children to play suggestively and to contradict details provided without the dolls, whereas the older children were more likely to provide details that were consistent. Children in both age groups produced proportionally more fantastic details with the dolls than without the dolls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hepatitis C infection risk analysis: who should be screened? Comparison of multiple screening strategies based on the National Hepatitis Surveillance Program

Children with cerebral palsy (CP) display postural problems, largely interfering with daily life activities. Clarification of neural mechanisms controlling posture in these children could serve as a base for more successful intervention. Studies on postural adjustments following horizontal forward and backward displacements of a movable platform in ten school-age children with spastic diplegia and non-disabled controls revealed that sitting CP children, like standing CP children, show direction specific postural adjustments, indicating that the basic pattern of muscle coordination in these conditions is conserved. Dysfunctions are especially present in the modulation of the response pattern of ventral muscles during forward translations. They consist of: (1) a stereotyped and non-variable activation of all ventral muscles; (2) an abnormal top-down muscle recruitment; and (3) an excessive degree of antagonistic co-activation. The altered patterns of muscle coordination could be the result of two interacting mechanisms, the primary deficit due to the early brain damage and a compensation due to the postural instability. Especially the latter dysfunction furnishes opportunities for therapeutic help.     

Parental scaffolding of young children's spatial communication.

Two studies documented and evaluated parental scaffolding of 3- and 4-year-olds' spatial communication. In Study 1, children gave directions to parents about locations of objects. Three-year-olds gave ambiguous directions more often than 4-year-olds, and parents used directive prompts more often with 3-year-olds than 4-year-olds. Study 2 compared the effectiveness of parental prompts in a controlled experiment. Each time children gave ambiguous directions, they were given either a directive prompt, nondirective prompt, or no prompt. Both age groups benefitted from directive prompts, but 3-year-olds benefitted less than 4-year-olds from nondirective prompts. Discussion focuses on parents' sensitivity to children's scaffolding needs and on developmental differences in children's responses to scaffolding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prevalence of ocular disorders among 6- and 7-year-olds in Santa Monica, California

BACKGROUND: Undetected ocular disorders can cause serious problems in a child's mental and social development. METHODS: To investigate relationships between ocular disease, gender and ethnicity in children, vision screening examination data was analyzed from the UCLA Mobile Eye Clinic (MEC), collected from 1985 to 1990 on first graders (69.9 percent 6- and 30.1 percent 7-year-olds) in Santa Monica, California. RESULTS: The sample consisted of 1,469 individuals, of whom 48.1 percent were female and 51.9 percent were male. Ethnicity data was available from 1988 to 1990 on 834 individuals, of whom 46.9 percent were Hispanic, 27.9 percent were White. 11.5 percent were Black, 4.4 percent were Asian, and 9.2 percent were of other races. Significantly more females than males had refractive errors, specifically hyperopia and astigmatism, and uncorrected visual acuity of 20/50 or worse in at least one eye. There were no significant associations of ethnicity or sex with any other disease category. The overall prevalences of other diseases were less than 4 percent. Of the 6- and 7-year-olds studied in Santa Monica, California, 18.5 percent had refractive errors. CONCLUSIONS: Screening for ocular disorders at an early age allows for detection of problems, especially refractive errors, that might affect school performance if uncorrected.     

The effect of drawing on memory performance in young children.

In Experiment 1, 32 5- to 6-year-old boys and girls participated in a unique event and were interviewed about that event 1 day later. Half of the children were asked to draw what happened during the event and half were asked to tell what happened. In both conditions, only children's verbal behavior was scored. Children in the draw group were as accurate and reported more information than children in the tell group, especially in response to direct questions. In Experiment 2, 32 5- to 6-year-olds and 32 3- to 4-year-olds participated in the same event used in Experiment 1 and were interviewed 1 month later. The 5- to 6-year-olds in the draw group reported more information than the 5- to 6-year-olds in the tell group after the 1-month delay. Drawing did not, however, increase the amount of information reported by 3- to 4-year-olds. These findings have important theoretical implications for memory development and important practical implications for children's eyewitness testimony. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Worldwide variations in prevalence of symptoms of allergic rhinoconjunctivitis in children: the International Study of Asthma and Allergies in Childhood (ISAAC)

BACKGROUND: As part of the International Study of Asthma and Allergies in Childhood (ISAAC), prevalence surveys were conducted among representative samples of school children from locations in Europe, Asia, Africa, Australia, North and South America. SUBJECTS: 257,800 children aged 6-7 years from 91 centres in 38 countries, and 463,801 children aged 13-14 years from 155 centres in 56 countries. METHODS: Written symptom questionnaires were translated from English into the local language for self-completion by the 13-14-year-olds and completion by the parents of the 6-7-year-olds. Rhinitis was described as a problem with sneezing, or a runny, or blocked nose when you (your child) DID NOT have a cold or the flu. Additional questions were asked about rhinitis associated with itchy-watery eyes, interference with activities and a history of hay fever ever. RESULTS: The prevalence of rhinitis with itchy-watery eyes ("rhinoconjunctivitis") in the past year varied across centres from 0.8% to 14.9% in the 6-7-year-olds and from 1.4% to 39.7% in the 13-14-year-olds. Within each age group, the global pattern was broadly consistent across each of the symptom categories. In centres of higher prevalence there was great variability in the proportion of rhinoconjunctivitis labelled as hay fever. The lowest prevalences of rhinoconjunctivitis were found in parts of eastern Europe, south and central Asia. High prevalences were reported from centres in several regions. CONCLUSION: These results suggest substantial worldwide variations in the prevalence and labelling of symptoms of allergic rhinoconjunctivitis which require further study. These differences, if real, may offer important clues to environmental influences on allergy.     

Posture, locomotion, spatial orientation, and motion sickness as a function of space flight

This article summarizes a variety of newly published findings obtained by the Neuroscience Laboratory, Johnson Space Center, and attempts to place this work within a historical framework of previous results on posture, locomotion, motion sickness, and perceptual responses that have been observed in conjunction with space flight. In this context, we have taken the view that correct transduction and integration of signals from all sensory systems is essential to maintaining stable vision, postural and locomotor control, and eye-hand coordination as components of spatial orientation. The plasticity of the human central nervous system allows individuals to adapt to altered stimulus conditions encountered in a microgravity environment. However, until some level of adaptation is achieved, astronauts and cosmonauts often experience space motion sickness, disturbances in motion control and eye-hand coordination, unstable vision, and illusory motion of the self, the visual scene, or both. Many of the same types of disturbances encountered in space flight reappear immediately after crew members return to earth. The magnitude of these neurosensory, sensory-motor and perceptual disturbances, and the time needed to recover from them, tend to vary as a function of mission duration and the space travelers prior experience with the stimulus rearrangement of space flight. To adequately chart the development of neurosensory changes associated with space flight, we recommend development of enhanced eye movement systems and body position measurement. We also advocate the use of a human small radius centrifuge as both a research tool and as a means of providing on-orbit countermeasures that will lessen the impact of living for long periods of time with out exposure to altering gravito-inertial forces.     

Planning in human children (Homo sapiens) assessed by maze problems on the touch screen.

The authors examined how human children perform on maze tasks on the touch screen and whether the children plan the solution of the mazes. In Experiment 1, the authors exposed children around 3 years of age to a maze having an L-shaped line as a barrier that can be solved by moving an illustration of a dog (the target) to that of a bone (the goal) with their fingers. The participants successfully solved the maze by taking efficient routes more frequently than chance, although the authors found no evidence that a preview of the maze before starting to solve the task facilitated their performance. In Experiment 2, using a plus-shaped maze, the authors found that 3- and 4-year-old children plan and adjust their moves while solving the maze, with 4-year-olds showing more advanced and higher-level planning than 3-year-olds. Similarity of these results to what the authors previously found in pigeons tested in the same tasks may suggest an analogy for planning capacity in the behavioral level across taxa and developmental stages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young children's representation of spatial information acquired from maps.

The early development of the ability to acquire integrated knowledge of a space from a map was investigated in 130 children, 4 to 7 years of age. Experiment 1 demonstrated that all 6- and 7-year-olds and many 4- and 5-year-olds could learn the layout of a large playhouse composed of six adjoined rooms by memorizing a map. Children who learned the map before entering the playhouse more quickly learned a route through it than children who were not exposed to the map, and older children performed significantly better than younger children. In Experiment 2 preschoolers learned a map of a space that contained six spatially separated small rooms within one large room. Children could therefore view the entire configuration of smaller rooms as they traveled around the larger room. Preschoolers performed significantly better in Experiment 2 than in Experiment 1, and the majority of them performed perfectly or almost perfectly. Taken together, the findings help to clarify young children's map-reading abilities in several respects and suggest that preschoolers' abilities are more substantial than has been assumed or demonstrated previously. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Setting goals to switch between tasks: Effect of cue transparency on children’s cognitive flexibility.

Three experiments examined the difficulty of translating cues into verbal representations of task goals by varying the degree of cue transparency (auditory transparent cues, visual transparent cues, visual arbitrary cues) in the Advanced Dimensional Change Card Sort, which requires switching between color- and shape-sorting rules on the basis of cues. Experiment 1 showed that 5- and 6-year-old children’s performance improved as a function of cue transparency. Experiment 2 yielded the same pattern of results and showed that cue transparency effects cannot be accounted for by cue format only. Finally, Experiment 3 examined the effect of cue transparency in 7- and 9-year-olds and adults. The effect decreased over age for accuracy performance but not for latencies, suggesting that under some conditions, the difficulty of cue translation can still be observed in individuals whose inner speech is efficient. Overall, these findings showed that goal setting substantially contributes to children’s flexible behaviors and continues to influence adults’ performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mental disorders in the offspring of alcoholic fathers (children from an early age to 28)

The examined groups included 175 children whose fathers were alcoholics and 73 individuals from nonalcoholic parents. The study group was divided by age into children from infantile age to 15 years and 16-28-year-olds. The wide range of psychopathologic disorders were revealed in children up to 15 years of age: syndrome of hyperactivity, neurotic disturbances, mental retardation, epileptic-like syndrome. Alcoholism was found in sons only (3.77%). Mental disorders were revealed significantly more frequently in sons of alcoholic fathers than in their daughters. Their incidence increased with the age of the sons. The disturbances occurred significantly more frequently in the test group as compared with the control one (19 and 6.38%, respective by). In the older group (16-28-year-olds) the spectrum of mental disorders consisted of alcoholism, mental retardation, psychopathic-like and neurotic disorders. Alcoholism occurred most frequent and its rate depended on the age and sex. Frequency of alcoholism was 66.7% in sons aged 21-28 years and 15.38% in daughters of the same age. The conclusion was made about multiple risk for children of alcoholic fathers. More vulnerable contingent was the sons for which the risk of alcoholism was very high.     

Body composition determined with MR in patients with Duchenne muscular dystrophy, spinal muscular atrophy, and normal subjects

OBJECTIVE: To examine the feasibility of using spectral analysis techniques to identify potential biomarkers of diminished postural control in elderly individuals. DESIGN: Data from spectral signatures (derived from postural sway) of 21 young adults and 42 elderly individuals classified as "high" or "low" risk with regard to functional balance capacity were analyzed using Risk Category (3) x Sensory Condition (3) multivariate analyses of variance. Postural control was challenged by varying the visual conditions under which individuals stood on a measurement platform. RESULTS: Results indicated that measures of central tendency and dispersion of the spectral frequency distribution from medial-lateral components of sway (but not antero-posterior sway) clearly differentiated between "high" and "low" risk elderly. Low risk elderly were not different from young adults. High risk elderly exhibited greater dispersion and lower mean frequency than other groups. CONCLUSIONS: Differences in spectral characteristics of medial-lateral components of sway were more related to risk category than to age. Elderly persons with high functional balance capacity displayed characteristics similar to those of young adults. Thus, spectral frequency analysis techniques may be a clinically useful tool for identifying individuals potentially at risk of falling.