Rate Changes in Spontaneous Neuronal Impulse Sequences

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Abstract
Heino, T. A., J. Hyvarinenand A. R. A. Sovijärvi,Rate changes in spontaneous neuronal impulse sequences. Acta physiol. scand. 1970.78. 529–538.Sudden rate changes in spontaneous activity were seen in 16 cells of 373 examined under light urethane anesthesia in various diencephalic, striatal, and limbic areas of rabbits. The stochastic properties of the rate varying impulse sequences were examined with statistical techniques. In this material, the dispersion of impulse interval lenghts was a uniform function of the mean discharge rate. For a range of spontaneous activity from 1.5 to 73 imp/sec, this relation was adequately expressed by the equation s=1.42 m1.42, wheremis the mean interval in seconds and s is the standard deviation of the interval lengths in seconds. This relation held for means and standard deviations from different cells as well as for different values from the same cell. In one half of the cells, a time series analysis revealed no change in the stochastic properties of the impulse sequence at the time of the rate change. In other cells, a periodic, rhythmic activity was disclosed during slower discharge rates, but it was not present in the faster activity; or vice versa. In yet other cells, the changes in mean discharge rate were paralleled by similar changes in the frequency of the rhythm. Except for the rhythmic periodicity, all the stochastic properties examined were related to the mean frequency of firing.