Scalp and depth EEG were obtained during thalamotomy in 19 Parkinsonian patients, and a correlation analysis was performed to demonstrate additional information. 1) The decrease in mean frequency of alpha and increase in theta activity constituted a characteristic feature in Parkinsonism. The degree of these findings was closely related to the progression of the disease. 2) Simultaneous recordings in the thalamus and the scalp tended to show approximate spectral values in mild cases, but demonstrated some differences as the disease progressed. 3) Comparison of scalp and thalamic recordings revealed the existence of coincident and independent alpha activities in each area. 4) Cross-correlation analysis of the scalp EEG revealed that there were some progessive changes in phase relationships, including advance of activities from the front and delay of from the occiput with phase shifts over 90°. 5) Travelling waves were also found in the depth EEG, and the direction was from the thalamus to the cortex in some cases, but reversed in others. The phase shifts of alpha activities between the scalp and the thalamus were from 10° to 90°. From these values, the conduction velocity of the spreading alpha were from 2.4m/s to 21.6m/s.
Alpha activity Correlation analysis