THE BASAL ganglia and the substantia nigra are now generally accepted as the chief sites of pathological changes in the parkinsonian states (paralysis agitans; postencephalitic and arteriosclerotic parkinsonism). It has been suggested that these changes remove or interfere with an inhibitory function of these parts, the characteristic tremor originating elsewhere or representing the pyramidal system functioning without extrapyramidal constraint.
A 6 per second rhythm, known as the theta rhythm, can be recorded from the cerebral cortex. It is believed that this is "paced" by basal ganglia mechanisms. On a few occasions this theta rhythm has been inhibited by the inhalation of amyl nitrite.1 It appeared worth while, therefore, to try the effects of such inhalations on the tremors characteristic of diseases of the basal ganglia, even though abnormal electroencephalograms have been found to occur only in those cases of postencephalitic parkinsonism in which personality changes, and not tremor, were
GARAI O. TREMOR IN PARKINSON'S DISEASE AND ITS INHIBITION BY AMYL NITRITE. AMA Arch NeurPsych. 1951;65(4):452-462. doi:10.1001/archneurpsyc.1951.02320040042003