Age-based stereotype threat effects on dynamic balance in healthy older adults.

Introduction: Stereotype threat can lead older adults to perceive their experiences in a biased manner, giving rise to interfering thoughts and negative emotions that generate stress and anxiety. Negative beliefs about aging may serve as an additional factor that increases the need for attentional demand, potentially resulting in a performance level below their actual capabilities. In the present study, we asked whether negative aging stereotypes influence a dynamic balance task and explored the means to counteract them in healthy elderly participants.

Ego- and Geo-Centered References: A Functional Neuroimagery Study.

Introduction: The integration of vestibular, visual, and somatosensory cues allows the perception of space through the orientation of our body and surrounding objects with respect to gravity. The main goal of this study was to identify the cortical networks recruited during the representation of body midline and the representation of verticality.

Methods: Thirty right-handed healthy participants were evaluated using fMRI.

Representation of Body Orientation in Vestibular-Defective Patients Before and After Unilateral Vestibular Loss.

The unilateral vestibular syndrome results in postural, oculomotor, perceptive, and cognitive symptoms. This study was designed to investigate the role of vestibular signals in body orientation representation, which remains poorly considered in vestibular patients. The subjective straight ahead (SSA) was investigated using a method disentangling translation and rotation components of error.

Signs of spatial neglect in unilateral peripheral vestibulopathy.

Background And Purpose: In this study, the question of whether egocentric representation of space is impaired in chronic unilateral vestibulopathies was examined. The objective was to test current theories attributing a predominant role to vestibular afferents in spatial cognition and to assess whether representational neglect signs are common in peripheral vestibular loss.

Methods: The subjective straight-ahead (SSA) direction was investigated using a horizontal rod allowing the translation and rotation components of the body midline representation to be dissociated in 21 patients with unilateral vestibular loss (right, 13; left, eight) and in 12 healthy controls.

Unilateral vestibular deafferentation impairs embodied spatial cognition.

A growing number of studies indicate that cognitive complaints are common in patients with peripheral vestibular disorders. A better understanding of how vestibular disorders influence cognition in these patients requires a clear delineation of the cognitive domains affected by vestibular disorders. Here, we compared the consequences of left and right vestibular neurectomy on third-person perspective taking-a visuo-spatial task requiring mainly own-body mental imagery, and on 3D objects mental rotation imagery-requiring object-based mental imagery, but no perspective taking.

Functional Neuroanatomy of Vertical Visual Perception in Humans.

Vertical representation is central to posture control, as well as to spatial perception and navigation. This representation has been studied for a long time in patients with vestibular disorders and more recently in patients with hemispheric damage, in particular in those with right lesions causing spatial or postural deficits. The aim of the study was to determine the brain areas involved in the visual perception of the vertical.

Do Visual and Vestibular Inputs Compensate for Somatosensory Loss in the Perception of Spatial Orientation? Insights from a Deafferented Patient.

The present study aimed at investigating the consequences of a massive loss of somatosensory inputs on the perception of spatial orientation. The occurrence of possible compensatory processes for external (i.e.

Improving postural control by applying mechanical noise to ankle muscle tendons.

The application of subthreshold mechanical vibrations with random frequencies (white mechanical noise) to ankle muscle tendons is known to increase muscle proprioceptive information and to improve the detection of ankle movements. The aim of the present study was to analyze the effect of this mechanical noise on postural control, its possible modulation according to the sensory strategies used for postural control, and the consequences of increasing postural difficulty. The upright stance of 20 healthy young participants tested with their eyes closed was analyzed during the application of four different levels of noise and compared to that in the absence of noise (control) in three conditions: static, static on foam, and dynamic (sinusoidal translation).

Changing perspective: The role of vestibular signals.

Social interactions depend on mechanisms such as the ability to take another person's viewpoint, i.e. visuo-spatial perspective taking.

Unilateral vestibular loss impairs external space representation.

The vestibular system is responsible for a wide range of postural and oculomotor functions and maintains an internal, updated representation of the position and movement of the head in space. In this study, we assessed whether unilateral vestibular loss affects external space representation. Patients with Menière's disease and healthy participants were instructed to point to memorized targets in near (peripersonal) and far (extrapersonal) spaces in the absence or presence of a visual background.

Biases in the perception of self-motion during whole-body acceleration and deceleration.

Several studies have investigated whether vestibular signals can be processed to determine the magnitude of passive body motions. Many of them required subjects to report their perceived displacements offline, i.e.

Unilateral and bilateral fatiguing contractions similarly alter postural stability but differently modify postural position on bipedal stance.

The aim of the present study was to compare the effects of unilateral and bilateral muscle fatigue on bipedal postural control and neuromuscular activities. Nineteen subjects completed bilateral fatiguing contractions (BI group), and seventeen subjects completed unilateral fatiguing contractions (UNI group) of the quadriceps femoris. Postural control, maximal voluntary contraction (MVC) and central activation ratio (CAR) were measured before and after the completion of fatiguing tasks for both groups.

Postural performance of vestibular loss patients under increased postural threat.

The effects of increasing postural task difficulty on balance control was investigated in 9 compensated vestibular loss patients whose results were compared to 11 healthy adults. Subjects were tested in static (stable support) and dynamic (sinusoidal translation of the support) conditions, both at floor level and at height (62 cm above the floor), and with and without vision, to create an additional postural threat. Wavelet analysis of the center of foot pressure displacement and motion analysis of the body segments were used to evaluate the postural performance.

Where is straight ahead to a patient with unilateral vestibular loss?

The vestibular system is classically associated with postural control, oculomotor reflexes and self-motion perception. The patients with vestibular loss are primarily concerned with balance and gait problems including head and trunk tilt and walking trajectory deviation to the lesioned side. These long-lasting postural and locomotor biases are thought to originate from changes in spatial perception of self.

Vestibular information is necessary for maintaining metric properties of representational space: evidence from mental imagery.

The vestibular system contributes to a wide range of functions, from postural and oculomotor reflexes to spatial representation and cognition. Vestibular signals are important to maintain an internal, updated representation of the body position and movement in space. However, it is not clear to what extent they are also necessary to mentally simulate movement in situations that do not involve displacements of the body, as in mental imagery.

Betahistine treatment improves the recovery of static symptoms in patients with unilateral vestibular loss.

Vestibular loss induces a combination of postural, oculomotor, and perceptive symptoms that are compensated over time. The aim of this study was to analyze the influence of betahistine dihydrochloride on vestibular compensation. A randomized, double-blind, placebo-controlled study was performed in Menière's disease patients who underwent a curative unilateral vestibular neurotomy (UVN).

Disturbance of contralateral unipedal postural control after stimulated and voluntary contractions of the ipsilateral limb.

One session of sustained unilateral voluntary muscular contractions increases central fatigue and induces a cross-over of fatigue of homologous contralateral muscles. It is not known, however, how this cross-transfer affects contralateral unipedal postural control. Moreover, contralateral neurophysiological effects differ between voluntary muscular contractions and electrically stimulated contractions.

Stimulated and voluntary fatiguing contractions of quadriceps femoris differently disturb postural control.

Muscle fatigue affects muscle strength and postural control. However, it is not known whether impaired postural control after fatiguing muscular exercise depends on the nature of the muscle contraction. To answer this question, the present study analyzes changes in postural control after two fatiguing exercises of equal duration and intensity but that induced different magnitudes of strength loss.

Tell me your vestibular deficit, and i'll tell you how you'll compensate.

Most patients with unilateral vestibular loss exhibit a similar static and dynamic vestibular syndrome consisting of vestibulo-ocular, posturolocomotor, and perceptive deficits. This vestibular syndrome recovers more or less completely and more or less rapidly over time. One open question is whether recovery mechanisms differ according to vestibular pathology and/or patients.

Dental occlusion and postural control in adults.

We studied the influence of a dental occlusion perturbation on postural control. The tests were performed in three dental occlusion conditions: (Rest Position: no dental contact, Maximal Intercuspal Occlusion: maximal dental contact, and Thwarted Laterality Occlusion: simulation of a dental malocclusion) and four postural conditions: static (stable platform) and dynamic (unstable platform), with eyes open and eyes closed. A decay of postural control was noted between the Rest Position and Thwarted Laterality Occlusion conditions with regard to average speed and power indexes in dynamic conditions and with eyes closed.

How body position changes visual vertical perception after unilateral vestibular loss.

Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral vestibular loss. The present study was designed to investigate whether body position (standing upright, sitting on a chair and lying supine) influences the visual vertical perception in Menière's patients tested before and after a unilateral vestibular neurotomy. Data were compared with sex- and age-matched healthy participants.

Changes of visual vertical perception: a long-term sign of unilateral and bilateral vestibular loss.

This study investigates how unilateral and bilateral vestibular deafferentation modifies visual vertical perception in the presence of dynamic and static visual cues. We tested 40 Menière's patients before and after (from 1 week to 1 year) a curative unilateral vestibular neurotomy (UVN), and 4 patients with bilateral vestibular loss. Patients' performances were compared with those of 24 healthy subjects.

Visual field dependence-independence before and after unilateral vestibular loss.

To investigate whether visual field dependence-independence changed after unilateral vestibular loss, Menière's patients were tested before and after unilateral vestibular neurotomy and compared with controls. Using the rod and frame test, visual vertical perception was tested under four visual contexts (with a frame tilted either clockwise or counterclockwise, with a vertical frame, and without visual reference). Both controls and Menière's patients before unilateral vestibular loss split into visual field dependent and independent subpopulations.

Direction and distance deficits in path integration after unilateral vestibular loss depend on task complexity.

The effects of peripheral vestibular disorders on the direction and distance components of the internal spatial representation were investigated. The ability of Menière's patients to perform path integration was assessed in different situations aimed at differentiating the level of spatial processing (simple versus complex tasks), the available sensory cues (proprioceptive, vestibular, or visual conditions), and the side of the path (towards the healthy versus the lesioned side). After exploring two legs of a triangle, participants were required either to reproduce the exploration path, to follow the reverse path, or to take a shortcut to the starting point of the path (triangle completion).

Torsional optokinetic nystagmus after unilateral vestibular loss: asymmetry and compensation.

The aim of this study was to analyse torsional optokinetic nystagmus (tOKN) in 17 patients with Menière's disease before and after (1 week, 1 month and 3 months) a curative unilateral vestibular neurotomy (UVN). The tOKN was investigated during optokinetic stimulations around the line of sight directed towards either the lesioned or the healthy side, at various constant angular velocities. Dynamic properties of tOKN and static ocular cyclotorsion were analysed using videonystagmography.