Abstract
The periodic fluctuations in the amplitudes of the evoked potential produced by intermittent light stimulation of low frequencies were analyzed for a variety of areas such as the cortex, specific and nonspecific nuclei and midbrain reticular formation in the cat's brain. From the periodic time, four types of fluctuations were found, i. e., type I, 30-50 sec; type II, 7-12 sec; type III, 3-5 sec; and type IV, 0.7-1 sec. These were almost the same as the classification of the fluctuations in the alpha wave in man. The following characteristics were found in each type of fluctuation.
Type I fluctuation showed an excitability change common to the entire nonspecific system, including the cortex, regardless of the site or the component of the evoked potential.
Type II fluctuation was an excitability change of nonspecific origin and showed an antagonistic pattern between CM and the RF-cortex system.
Type III fluctuation showed an independent activity in CM and RF, and the type III activities in CM and RF separately affected the cortex.
Type IV fluctuation was a local activity in each portion of the brain and had a closer relationship within the specific system, rather than within the nonspecific one, as compared with other types.
The functions and physiological or biological significance of these periodic fluctuations of excitability were discussed through comparisons with different periodic phenomena in the central nervous system.
