On Earth, the subjective sense of vertical is due to many inputs from specialised sensors located in the eye, in the inner ear, and in joints and muscles. More recently, a further contribution to the detection of subjective vertical was observed from visceral receptors sensitive to blood mass shifts, mainly located in the kidneys and in the thorax. The aim of this present experiment is the analysis of visceral receptor performance within an environment, which rules out possible bias due to visual and gravitational inputs.
Analysis will be performed pre-, during and post-flight with an instrument called a Subjective Vertical Analyser (SVA), which will provide a completely darkened environment. During flight, the experiment will include the manipulation of body fluid mass with the use of a Lower Body Negative Pressure device. This is a standard method to shift fluids into the lower extremities of the body through suction. This manipulation will help in determining the role that the visceral receptors may play in finding the subjective vertical.
Globally, this study could contribute to clarify the role that these receptors play in the detection of body axis both on Earth and under microgravity, and increase scientific knowledge on spatial orientation and flight safety.
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