Symposium on the Role of the Vestibular Organs in Space Exploration (1970) / Chapter Skim
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ELECTROPHYSIOLOGICAL EXPERIMENTS ON THE ISOLATED SURVIVING LABYRINTH OF ELASMOBRANCH FISH TO ANALYZE THE RESPONSES TO LINEAR ACCELERATIONS
ELECTROPHYSIOLOGICAL EXPERIMENTS ON THE ISOLATED SURVIVING LABYRINTH OF ELASMOBRANCH FISH TO ANALYZE THE RESPONSES TO LINEAR ACCELERATIONS
Pages 161-166
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From page 161... ...
Whereas it is generally assumed that the semicircular canal is stimulated exclusively by angular acceleration and provides the central nervous system with integrated information relating to angular velocity at any given moment, the otolith organ, although capable of being stimulated by changes in angular velocity, is chiefly concerned with the monitoring of linear accelerations in the form of gravitational, centrifugal, translatory, and oscillatory stimuli, the last belonging to the field of vibration and sound. The assumption that semicircular canals are exclusively stimulated by angular acceleration, and not at all by linear acceleration, has been challenged in the past, but has recently come under renewed and serious scrutiny in the light of a number of experiments in which it was found that responses to angular acceleration, i.e., perrotatory and postrotatory nystagmus, perrotatory and postrotatory impulse activity chiefly in second-order neurons in vestibular centers, as well as the subjective experience of human observers, are significantly modified by centrifugal effects and by simultaneous changes of head position in space.
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From page 162... ...
When the emphasis is on quantitative aspects, the study of single units may be considered preferable, if not imperative, although useful results have been obtained by the analysis of the electronic integration of responses based on the recordings of massive multifiber response pictures. Single-unit peripheral preparations are relatively easily obtainable from the dendriti |
From page 163... ...
On their passage through the foramina of the elasmobranch labyrinth capsule, the branches of the eighth nerve are packed in a highly viscous jelly which obviously serves the purpose of establishing a leakproof barrier between perilymphatic space and the brain case. Centrally to this passage the nerve disperses into a brain-type tissue organization which makes it quite impossible to isolate strands containing recordable single units.
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From page 164... ...
Although, with the preparative methods used so far, a large proportion of the vertical ampullae and somewhat fewer of the horizontal ones proved to be positionsensitive immediately after isolation and therefore to react to gravitational stimulation, only a small percentage have so far yielded significant responses to stimulation by a rotating linear vector. The threshold was high and only in one case did the response amount to much at 30 rpm (0.3 g)
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From page 165... ...
There are, however, not a few instances of the total absence of a response to the rotating linear vector both in horizontal and vertical ampullae. Finally, there is yet another type of situation in which linear acceleration has been claimed to have modified the response from the semicircular canal.
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From page 166... ...
. , , the semicircular canals, and we predict that the semicircular ment.
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