By divising a method to record arm-deviation during the test of perrotary or optokinetic nystagmus, the relation between arm deviation and nystagmus was investigated. For this purpose the following procedure was performed. The subject was asked to sit on an electrically driven turning chair and repeatedly swung the "knob" horizontally with a constant amplitude and frequency. Handling of the knob, which was set on the turning chair, was done with the right arm slightly extended in front of the subject. Movement of this knob could be recorded electrically as serial sine curves. This graph was named "arm-kine-tograph". The center line of arm-kinetograph, by which arm-deviation could be detected, was traced by a "signal processor 7TO7A".
Change of amplitude and frequancy in arm-kinetogragh could be analysed by the same computer.
Rotatory stimulation was used for this investigation as follows.: The subject with eyes securely blindfolded sat on the turning chair with the head bent forward 30 degrees. The chair was rotated with the trapezoidal method. Stimulation of±2, 4, 6 and 8°/sec
2 were used for every 10 seconds. The chair was first rotated clockwise and then contraclockwise. In order to eliminate the influence of the previous turning, the subjects rested for 4 minuits between measurements. During this rotation test, parotatory nystagmus, arm-deviation and velocity of the turning chair were recorded at the same time. In application of optokinetic stimulation, the drum, which had black and white stripes incide it, was rotated around the subject with triangular method of±4°/sec
2.
During this test, optokinetic nystagmus (OKN), arm-deviation and rotation velocity of the drum were recorded at the same time.
The arm-kinetograph of 34 normal subjects were investigated and the following results were obtained:
1) Arm-kinetograph in non-stimulated conditions
At the beginning of recording, the center line of arm-kinetograph fluctuated irregularly. But after short training, it became stable.
2) Change in arm-kinetograph of normal subjects induced by rotatory stimulation
After the stability of the center line in the arm-kinetograph was obtained, rotatory stimulation was applied. The incidence of arm-deviation and the magnitude of the maximum arm-deviation increased in accordance with the strength of rotatory stimulation.
The subjects with dominant arm-deviation had a tendency to show large amplitudes of perrotatory ny-stagmus. Most of maximum arm-deviation appeared after the occurrence of the nystagmus which had the maximum eye-speed of the slow phase.
It was interesting that the direction of arm deviation induced by weaker stimuli (2, 4°/sec
2) mostly corresponded with the quick phase of perrotatory nystagmus, while that of stronger stimuli (6, 8°/sec
2) had a tendency to be directed to the slow phase of nystagmus. On the other hand, amplitude and frequency in the arm-kinetograph of normal subjects were not influenc ed by rotatory stimulation, while the dysmetric and arrhythmic change of the arm-kinetograph of those with cerebellar disease were manjfested by application of rotatory stimulation.
3) Changes in the arm-kinetograph of normal subjects induced by optokinetic stimulation.
Arm-deviation induced by optokinetic stimulation had a tendency to be directed to the quick phase of OKN at slow speeds of the drum, but the direction was changed to the opposite side at high speeds of the drum. In most cases the maximum arm-deviation appeared after the occurrence of the nystagmus which had the maximum eye speed of the slow phase. The amplitude and frequency of the normal arm-kinetograph were not influenced by optokinetic stimulation, while the dysmetric and arrhythmic changes of those with of cerebellar disease were manifested by the same stimulation.
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