Motion sickness: part II--a clinical study based on surgery of cerebral hemisphere lesions.

Man has always been intrigued with the localization of function within the brain but has paid insufficient attention to the long and the short association fiber pathways which, when stimulated, may fire distant areas evoking unusual responses. Three cases of intracerebral lesions are presented to demonstrate the significance of these structures. The vestibular symptoms of dizziness may occur from excitation of the temporal operculum. If, added to this symptom, the patient has spatial disorientation, such as feeling upside down, it suggests that the region of the supramarginal gyrus and the angular gyrus are involved. When unformed visual hallucinations (such as flashes of light) or formed hallucinations (such as distorted images) are present the occipital and midtemporal regions of the brain, respectively, are considered to be the sources of such responses. The symptoms described above were reminiscent of those experienced by some of the cosmonauts and astronauts and it called the authors' attention to this "motion sickness in space." The areas from which such responses may be elicited are the temporoparieto-occipital regions, which are nourished by the posterior cerebral artery and its branches. Vascular insufficiency to this area by spasm of the vessel may be responsible for this symptomatology.