[Rhythmical processes in the cerebral cortex bioelectrical activity in arousal reaction: qualitative nonlinear...

An integral equation that takes into account the absolute and relative refractory periods of cortical cells was added to the earlier obtained integral equations describing the cooperation of excitatory and inhibitory neurons of the cerebral cortex, and its substantiation was suggested. The steady states and the stable region of oscillations of the mean membrane potential of excitatory neurons were investigated depending on the mean afferent influx value on the assumption of the normal threshold distribution of cells. The existence of a parameter multitude in the region of stability was shown when a suppression of the delta-rhythm and an enhancement of the theta-rhythm up to its dominance take place increasing nonspecific afferent influx, which shows up a white noise, and decrease of the theta-rhythm during further increase in nonspecific activation. Simultaneously the frequencies of the major cerebral rhythms increase. The conformity of the theoretically calculated dependences of changes of the spectrum upon increasing nonspecific afferent influx to the experimental data obtained during the electrical stimulation of the rabbit midbrain reticular formation was demonstrated.