Analysis of the theta-rhythm of the rabbit neocortex by estimation of particular coherence functions

Situations characterized by differences in the genesis of the theta-rhythm were distinguished by the analysis of activity recorded simultaneously from various points of the rabbit neocortex and hippocampus by means of the estimation of particular coherence functions. With maximal cross-correlation between potentials from different parts of the neocortex, in most cases (not less than 75%) the high coherence of these potentials in the theta-band is determined by a theta-rhythm generated actually in the neocortex. In about 20% of cases the high coherence of these potentials may be the result of the passive conduction of hippocampal theta-activity to the surface of the neocortex. To increase the likelihood of the passage of excitation from the afferent to the effector system active generation of rhythmic waves in the theta-band in both the neocortex and hippocampus is essential. Rhythmic processes in both structures must be coherent with each other.