ON THE CONTRIBUTION OF VISCERAL RECEPTORS TO THE SENSE OF SUBJECTIVE VERTICAL (VISUAL
SUBJECTIVE VERTICAL)
Research Area: Nervous and Vestibular Systems
Expedition(s): 10, 11
Principal Investigator(s): ● Colonel Enrico Tomao, Italian Air Force, Rome, Italy
RESEARCH OBJECTIVES
On Earth, the subjective sense of vertical is due to many sensory inputs, which are mainly
related to the visual, vestibular, and proprioceptive systems, utilizing special sensors located
respectively in the eye, inner ear, and in joints and muscles. A further contribution to the
detection of subjective vertical is observed from visceral receptors sensitive to blood mass
shifts, mainly located in the kidneys and in the thorax, specific data on the contribution of
visceral receptors to the detection of subjective vertical in a specific environment is still lacking.
The aim of this experiment is the analysis of visceral receptor performance in weightlessness.
RESULTS
The subjective visual vertical (SVV) can be significantly influenced by the presence of a
displaced visual field, as in the case of the rod and frame test (RFT). A series of studies showed
the effects of blood mass shifts to and from the lower limbs on SVV due to visceral
mechanoreceptors (VM) located at the level of the kidneys and of the thorax. These sensors
may be artificially activated with a lower body negative pressure (LBNP) device. In this study,
the role of visual and VM cues to orientation perception were evaluated using the RFT and the
LBNP devices under a microgravity environment. A preliminary investigation was conducted in a
sample of military pilots to develop a RFT protocol to be used in microgravity environments.
This protocol was adopted to evaluate the contribution of VM to the SVV in a cosmonaut
before, during, and after a 10-day spaceflight, with and without concurrent activation of LBNP.
Subjective Vertical Analyser. ESA image. Eye Movement Recording Subsystem
Electronics Box. NASA image.