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Unusual vestibular responses to head movements in weightlessness may produce spatial orientation illusions and symptoms of space motion sickness. An integrated set of experiments was performed during Spacelab 1, as well as before and after the flight, to evaluate responses mediated by the otolith organs and semicircular canals. A variety of measurements(More)
1. The synaptic connections of 44 single identified muscle spindle Ia afferents and of 21 Golgi tendon organ (Ib) afferents from medial gastrocnemius (MG) were studied in 46 cats by the spike-triggered averaging of synaptic noise in 803 motoneurons of various types. 2. The well-known monosynaptic Ia excitatory connections were confirmed and their(More)
A short-latency electromyographic response has been demonstrated in the human gastrocnemius during unexpected falls (11). The hypothesis that it is a form of otolith-spinal reflex has been tested in the cat. Electromyographic activity was measured in four muscles while suddenly and unexpectedly dropping a series of six cats from 50 cm above the ground. In(More)
(1) Gating currents were recorded from frog nodes of Ranvier treated either with toxins III or IV from the venom of the scorpion Centruroides sculpturatus or with the alkaloid toxin aconitine. (2) Toxins III or IV from Centruroides sculpturatus (which drastically reduce the sodium permeability PNa and slightly shift its voltage dependence in the(More)
In voltage clamped nodes of Ranvier inactivation of the sodium permeability is slowed by toxin V from the scorpion Centruroides sculpturatus, by sea anemone toxin ATX II or by internally applied KIO3. The slow decay of the Na inward current is markedly accelerated if the test pulse is preceded by a depolarizing conditioning pulse followed by a 10-500 ms(More)
The 4 payload crew members of the Spacelab Life Sciences 9-day space flight in 1991 were subjected to limited vestibular testing in flight as well as pre and post flight. Major differences in individual "perceptual style" appeared in their reaction to the visual-vestibular stimuli in the rotating dome experiment, and especially in the extent to which(More)
It is evident from the data reviewed that scorpion toxins can be distinguished on the basis of three properties: their effects on Na currents, their specific binding to excitable membranes, and the effects of depolarization and pH on binding and on effect. Additional work with other scorpion toxins is required to establish the degree of correlation between(More)
  • D G Watt
  • 1997
BACKGROUND Watt et al. (15) and Young et al. (17) have demonstrated that during prolonged microgravity, large errors can be made when pointing at memorized targets in the absence of vision. However, those experiments could not distinguish between errors caused by not knowing where the arm was pointed and errors caused by not knowing target location. The(More)
Reflex responses that depend on human otolith organ sensitivity were measured before, during and after a 10 day space flight. Otolith-spinal reflexes were elicited by means of sudden, unexpected falls. In weightlessness, "falls" were achieved using elastic cords running from a torso harness to the floor. Electromyographic (EMG) activity was recorded from(More)