[Experimental studies of motion sickness on board of a research ship]

To date the incidence and treatment of motion sickness have not been satisfactorily elucidated. Discrepancies among individuals in tolerating strong velocities and accelerations are well-known. To prevent motion sickness evaluations of individual predispositions are important. There are several current theories on the nature of motion sickness. These include the mismatching of sensory inputs, a Coriolis force, non-physiological stimuli and modulation of vestibuloocular reflexes (VOR). The main influence of the vestibular organ in generating kinetosis is obvious. Analysis of the chief movements of a ship demonstrates that linear acceleration is the principle factor in stimulating the vestibular organ. The moving gravity vector causes an intense otolith stimulation. By this means VOR is temporarily shut down. This effect can also be used for documenting motion sickness. A battery of vestibular tests was performed on the military research ship "Planet" during a 2-week autumny voyage on the Atlantic Ocean. Spontaneous nystagmus, bithermal bilateral responses and rotatory testing (slow harmonic acceleration) results were recorded by electronystagmography. Findings before starting and during the voyage were compared. A group of 3 unexperienced volunteers and 9 professional seamen were investigated. All unexperienced volunteers suffered from sea sickness, while none of the professionals showed any symptoms. At the beginning of the voyage the gain in nystagmus in harmonic acceleration testing was significantly lower in the professionals than in the unexperienced volunteers. During the voyage all professionals showed nearly constant gain values. All unexperienced individuals showed a decrease in gain only during the time of acute symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)