回転後眼振のモデルによる再検討

概要

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Postrotatory nystagmus was analyzed by a 2nd order system model in 15 healthy nomal subjects. In postrotatory nystagmus the input into the semicircular canal is the impulse, so the model was Y (t) =A/T1-T2× (e-t/T1-e-t/T2) y (t) : slow phase velocity T1 : short time constant T2 : long time constant A : amplitude By means of the least square method, the variables T1, T2 and A were calculated with the aid of a microcomputer. The subject was seated in the dark on a rotating chair which was stopped at 80/sec2, 120/sec2 and 160/sec2. The slow phase of the electro-nystagmogram on DC ENG recording was calculated every 2 minutes and its values were used to calculate the variables of the model. T1 (short time constant) at 80, 120 and 160/sec2 was 0.37, 0.5 and 0.67sec and T2 (long time constaant) was 12.8, 12.19 and 11.13sec, respectively. These values could be converted into the frequency range of postrotatory nystagmus by the equation : f=1/2T. The frequency range corresponding to the above values is 0.01 to 0.4Hz, which is considered to be the normal frequency range in postrotatory nystagmus testing.