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.

The directions of nystagmus and apparent self-motion evoked by caloric tests and angular accelerations.

Purpose: To further investigate the direction of (I) nystagmus and (II) self-motion perception induced by two stimuli: (a) caloric vestibular stimulations and (b) a sudden halt during vertical axis rotation.

Subjects And Methods: Twelve normal humans received caloric stimulation at 44 degrees C, 30 degrees C, and 20 degrees C while in a supine position with the head inclined 30 degrees upwards. In a second test they were rotated around the vertical axis with the head randomly placed in two positions: tilted 30 degrees forward or tilted 60 degrees backward, at a constant velocity of 90 degrees /sec for 2 minutes and then suddenly stopped.

Postural reflexes evoked by tapping forehead and chest.

We investigated whether a tap with a reflex hammer to the forehead can elicit responses in the leg muscles and whether vestibular stimulation is the crucial prerequisite for eliciting these responses. We also measured the postural changes caused by the tap and by the compensatory, presumably reflex-like reactions of the subject. Tap-evoked activity of leg muscles was easily elicited during upright stance in normal subjects and was also seen in two subjects without vestibular function.

The human vertical optokinetic afternystagmus and the effect of gravity during pitch tilt.

Background: Findings concerning human vertical optokinetic afternystagmus (VOKAN) are often not consistent and in some cases even contradictory.

Method: VOKAN was studied in nine normal subjects using corneo-retinal potential technique and an infrared video camera detection apparatus (ISCAN). VOKAN responses were measured at three angles of pitch head (and body) tilt: 0 degrees (upright), 90 degrees (supine) and 135 degrees (45 degrees below horizontal).

Central nervous system impairment in diabetic patients.

The aims of this study were to investigate the function of the central motor control system in interaction with the vestibular and auditory systems (measured by H-reflex changes in response to vestibular and acoustic stimulations) in diabetics without clinical data for CNS impairment, in order to establish whether the disease affects these CNS mechanisms; and to assess this approach in detecting subclinical CNS diabetic pathology. The results show the same mode of change of H-reflex amplitude in response to acoustic and vestibular stimulations in diabetics as in normal subjects. However the degree of facilitation and inhibition was significantly (p < 0.

Cold caloric microcirculatory reflex disturbance in patients with Parkinson's disease.

The basal skin microcirculatory blood flow and its change in response to a cold caloric stimulus (cold water, 5 degrees C, exposure of one foot for 30 s) were investigated in nine patients with Parkinson's disease (PD) and nine normal subjects (controls). The results revealed a significant (p < 0.001) difference between the groups.

Vertical optokinetic nystagmus and after-responses during backward tilt.

Method: Vertical optokinetic nystagmus (VOKN) and after-responses were detected in nine subjects using the corneo-retinal potential (CRP) technique and an infrared video camera detection apparatus (ISCAN) simultaneously. The ISCAN method produced a much smaller inter-subject variability, a higher linear regression coefficient (0.94) when vertical eye position was regressed against vertical target position (+/- 30 degrees, 5 degrees increments).

Characteristics of the autonomic response in the visually evoked reflex in humans.

This study aimed (a) to investigate the effect of the visuogenic reflex on the skin microcirculation of the hand and foot, and (b) to compare it to that evoked by thermal stimuli. Fifteen volunteers took part in this study. The laser Doppler technique was used for measuring blood flow (BF).

Responses in skin microcirculation to vestibular stimulation before and during motion sickness.

Background: Observation of physiological changes during motion sickness is required to quantify the degree of sickness. The review of the literature does not show unifying results. An objective symptom of motion sickness is facial pallor.

Changes in interdigestive migrating electric complex induced by motion sickness.

This study aimed to investigate, by means of an intralumenal recording technique, the influence of motion sickness on the interdigestive migrating electric complex (IDMEC) of the gastrointestinal system of susceptible subjects. The results indicate that vestibular stimulations significantly change the duration of IDMEC phases (p < 0.05 and p < 0.