Abstract: In this study, discrimination reactions of 40 normal persons and 78 patients of neurathenia were compared. Before the psychotherapy, the wave amplitude of latency of reaction in the patients was greater than that in the normal persons. After the therapy, decreases in wave amplitude differed in individuals depending on the extents of their recovery: The wave amplitudes of completely recovered patients decreased to that extent as in normal persons and also a great decrease in the wave amplitude was seen in the basically recovered patients, but rather poorly recovered persons showed only a small decrease in the amplitude.As for the relationship between the wave amplitudes of latency of discrimination reaction tested before the therapy and the effects of therapy, one finds that most patients originally showing small wave amplitude recovered completely or basically after the treatment, but only small percentage of patients originally showing greate wave fluctuation recovered well.The wave amplitude of latency of discrimination reaction is one of the indices of the functional states of the cerebral cortex. The experiment carried out before the therapy demonstrates that functional states of patients' cortex were different from those of the healthy persons. The recovery of the functional states of cortex and the improvements in clinical symptoms go together. The patients with severe functional disorder recovered more slowly than those having the lesser disorder.From this study, the author concludes that the wave amplitude of the latency of discrimination reaction can be used in diagnosing the severity of illness and also the effect of treatments,

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