Application of Psychophysics to the Exploration of Minamata Disease (methylmercury Poisoning), Which Disturbs Sensory Cortex

Minamata disease (MD), a methylmercury poisoning from fish and shellfish contaminated by Chisso Company waste discharge, was found in 1956. Small input neurons of the cerebral cortex in the fourth layer including somatic, visual, auditory, tasting, and olfactory areas are destroyed in MD. Several ten thousand people were suffered from MD in the polluted area. But socio-economical environment, discrimination against MD patients, and the lack of the disease information concealed the vast spread of MD. Somatosensory disturbance is the main symptom of MD, but it has been ignored by the Government and so-called specialists for a long time. We have been succeeding in measuring sensory acuity by using psychophysical methods using fine abrasive papers and other quantitative methods. We would like to introduce these studies and discuss further exploration of other ways of studying cortical sensory systems.