[Formation of secondary focus in amygdala Kindling phenomenon of the rabbit: a study by the coherence method]

Formation of the secondary focus in the rabbit amygdala Kindling (K) phenomenon was analysed by the coherence method. This method is capable of showing the degree of correlation between two signals (EEG) at each frequency. Mature male rabbits were used and a train stimulation using a biphasic square wave of 60 Hz was applied to the amygdala for two second once a day until the completion of K-phenomenon. The results obtained were as follows. 1) The coherence values between the amygdaloid K-region and opposite amygdala were usually much higher than those of the cerebral cortex (motor and optic areas) with a frequency of 6 to 7 Hz before and after completion of the K-phenomenon. 2) The speed of the secondary focus formation was observed to be parallel with the coherence value. 3) The secondary focus formation induced by the K of amygdala in a rabbit has much to do with the 6 Hz nerve circuit which links between the primary focus and secondary focus. That is, if the coherence value appears high around 6 Hz, the secondary focus is easily formed in case of a rabbit. 4) Application of this method enabled us to see the degree of functional correlation between the primary focus and secondary focus at each frequency. With all these, it is suggested that the theta frequency ranges of power spectra between above region play a vital role in producing secondary focus formation of the amygdaloid Kindling in rabbits.