Astronauts eye-head coordination dysfunction over the course of twenty space shuttle flights.

Background: Coordination of motor activity is adapted to Earth's gravity (1 g). However, during space flight the gravity level changes from Earth gravity to hypergravity during launch, and to microgravity (0 g) in orbit. This transition between gravity levels may alter the coordination between eye and head movements in gaze performance.

Self-Motion Versus Environmental-Motion Perception Following Rotational Vestibular Stimulation and Factors Modifying Them.

Motion perception following rotational vestibular stimulation is described either as a self-motion or as an environmental-motion. The purpose of the present study was to establish frequency of occurrence of both sensations in healthy humans; what other sensations they experience and how factors insinuation and visual cues modify them. Twenty-four healthy subjects were rotated with constant velocity of 80°/s in four combinations of opened and closed eyes during the rotation and after a sudden stop.

Eye-Head Coordination in 31 Space Shuttle Astronauts during Visual Target Acquisition.

Between 1989 and 1995, NASA evaluated how increases in flight duration of up to 17 days affected the health and performance of Space Shuttle astronauts. Thirty-one Space Shuttle pilots participating in 17 space missions were tested at 3 different times before flight and 3 different times after flight, starting within a few hours of return to Earth. The astronauts moved their head and eyes as quickly as possible from the central fixation point to a specified target located 20°, 30°, or 60° off center.

Acquisition of Predictable Vertical Visual Targets: Eye-Head Coordination and the Triggering Effect.

The study was designed to investigate target acquisition in the vertical plane with emphasis on establishing strategy differences associated with acquisition triggering methods. Eight subjects were tested. Measurements consisted of target acquisition time, eye-head latency differences, velocity of gaze, eyes and head, and head amplitude.

Vestibular disorders following different types of head and neck trauma.

This review focuses on the published literature on vestibular disorders following different types of head and neck trauma. Current knowledge of the different causes and underlying mechanisms of vestibular disorders, as well as the sites of organic damage, is presented. Non-organic mechanisms are also surveyed.

Case Report of Vestibularly evoked Visual Hallucinations in a Patient with Cortical Blindness.

Previous work has shown that caloric vestibular stimulation may evoke elementary visual hallucinations in healthy humans, such as different colored lines or dots. Surprisingly, the present case report reveals that the same stimulation can evoke visual hallucinations in a patient with cortical blindness, but with fundamentally different characteristics. The visual hallucinations evoked were complex and came from daily life experiences.

Thresholds for self-motion perception in roll without and with visual fixation target--the visualvestibular interaction effect.

The purpose of this study was to establish the selfmotion perception threshold, in roll, in the visualvestibular interaction (VVI) state, creating an oculogyral illusion, and to compare this threshold to the self-motion perception threshold in darkness. A further aim was to investigate the dynamics of the threshold at a low frequency range (0.1-1 Hz) of sinusoidal rotation.

Vestibular and ocular motor function prior to and after therapeutic apheresis with small plasmafilter in multiple sclerosis.

Some patients with multiple sclerosis (MS) are resistant to steroid therapy. In them an alternative therapy could be therapeutic apheresis (TA). A woman with relapsing-remitting cerebral MS with dizziness and imbalance, resistant to steroid therapy was treated with low volume plasmapheresis with saline substitution.

Illusory self-motion perception evoked by caloric vestibular stimulation in sitting versus supine body positions.

The purpose of this study was to determine (i) if a change in the body position that alters the somatosensory afferentation and thus the signal integrated by sensory interaction influences the illusory self-motion perception evoked by cold calorics. If yes, (ii) is the direction of the provoked nystagmus also changed? The vestibular system in 47 healthy subjects was stimulated calorically with 20°C water while in supine and sitting positions but with the head fixed. After each procedure the subjects were asked to describe their self-motion experience, and the provoked nystagmus was analyzed.

Anxiety changes depersonalization and derealization symptoms in vestibular patients.

Background: Depersonalization and derealization are common symptoms reported in the general population. Objective. The aim of the present study was to establish the relationship between anxiety and depersonalization and derealization symptoms in patients with peripheral vestibular disorders.

Translation, cross-cultural adaptation and validation of the Bulgarian version of the Dizziness Handicap Inventory.

Purpose: The aim of the present study was the translation, cross-cultural adaptation and validation of the Dizziness Handicap Inventory in Bulgarian language (DHI-BG).

Methods: Ninety-seven vestibular patients (19 men and 78 women, mean age 45.08 ± 13.

Flash induced afterimage versus single spot visual object influence on visual-vestibular interaction in detection threshold for self-motion perception.

In seven healthy subjects we studied the effect of flash induced afterimage on perceptual threshold for self-motion during sinusoidal vertical axis rotation compared to rotation in darkness, and rotation with subject's gaze fixed on a 'real' visual object rotated with him. For a real object we used light-emitting diode (LED) aligned with subject's head. A MOOG motion platform was used to generate motion.

Asymmetrical loading during non-visual navigation.

Since previous studies showed that loading influences posture and gait, the aim of the present study was to determine the effect of asymmetrical loading on locomotion. The following questions were posed: is there a habituation to asymmetrical loading and what is the effect of immediate unloading? Nine healthy subjects (4 males and 5 females) were tested. They had to memorize visually a triangle drawn on the floor and then to walk clockwise and counterclockwise along it in darkness and blindfolded under the following conditions: baseline, loading of right shoulder with 20% of the body weight, after 30 min of habituation to the weight, and immediately after unloading.

Comparison of tap-evoked and tone-evoked postural reflexes in humans.

To find an easy clinical test of postural reflexes, we compared tone and tap stimuli for eliciting postural reactions in leg muscles in 13 healthy subjects during upright stance. Tones (1000 Hz, 90 dB nHl) were presented monaurally via headphones; taps were applied with a reflex hammer to the forehead. Surface EMG was recorded from the medial gastrocnemius and the sternocleidomastoid muscles, and rectified and averaged.

Cutaneous microcirculatory reaction to externally and internally applied cold caloric stimuli and its habituation.

The skin microcirculatory reaction to internally and externally applied cold stimuli and its habituation were studied in 10 subjects. Stimuli were applied, via drinking and injecting water (5 degrees C) through a probe into the stomach, and by immersing one foot in water (5 degrees C) 10 times, and the reaction was measured by a LDF. Results showed a decrease in the microcirculation after external stimulation, while no reaction was detected in response to internal stimulations.

Eye Coordination and Vestibular Testing in Electroconvulsive Therapy.

Nine depressive patients were examined before bilateral electroconvulsive therapy (ECT), immediately after ECT, and 2 days later with saccadic, pursuit tracking, and Hallpike caloric vestibular tests. Before ECT, all tests showed normal results. Immediately after ECT, the saccadic test displayed dysmetria of the fast eye movements in six of nine patients.